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| 2024-11-01 | 2025-04-15 | Clark | Monthly Summaries: Avalanches, Snowpack, and Weather: Pre-Season and November 2024: The fall weather in NW Montana was mostly sunny, warm, and dry until October 21st when the first winter storm of the season arrived. The Canyon floor received 1.00-1.50” of rain, but elevations above 6000’ accepted the first snowfall of the winter. The remainder of October was mostly dry until the 31st when an extended period of wet weather began and snowfall made it down to the Canyon floor. The National Weather Service issued its first Winter Storm Warning on November 4th, and the Program Area picked up 5-7” of snow above 6000’ and another 1.00” of water. We had dry conditions for only three days before another series of weak, but wet weather systems continued to build the winter’s snowpack. A more potent storm arrived on the 20th and lasted for three days. By sundown on the 23rd the Canyon floor had 10-14” of new snow and terrain above 6000’ received 12-24”. November finished cool with sub-freezing temperatures and light snowfall under mostly NW flow aloft. No avalanches were observed in November and snow depths ranged from 10-15” on the Canyon floor and 20-30” at our weather stations at 6400’. December 2024: November was consistently wet, but December alternated between a few storms and then long periods of dry weather. The month began with a week-long period of stable high pressure and dry weather. Air temperatures inverted with colder air settling down into the low elevation terrain. Meanwhile the high country basked in sunshine during the day and enjoyed milder temperatures. A small storm on Dec. 7th/8th brought an 1.00’ of water with freezing levels rising to 7000’. Another dry spell ensued from the 9th to the 13th. The snowpack was capped with a stout melt-freeze crust and was mostly stable with no avalanches observed in the Program Area. A more powerful storm finally arrived on December 18th, but it was warm with freezing levels again climbing up to almost 6000’ accompanied by strong westerly winds. The Canyon picked up an inch of water and elevations above the snow line received 6-8” of snow. Several avalanches occurred in the nearby Flathead Range and two, destructive-size 2 of 5 slab avalanches were observed in Grizzly Gulch in the Program Area. These were composed of the most recent storm snow and did not fail on an older snow buried deeper in the snowpack. The weather again turned mostly dry and partly sunny on the 19th and lasted through Christmas. The snowpack gained strength and no further avalanching occurred. January 2025: The month of January began with Canyon floor snow depths ranging from 20-25”, which is about average for that time of year. A powerful arctic front arrived from the NE on Jan. 3rd. and kicked up the Easterly winds. With all the loose, powder snow available for transport. Visibility improved the following day, and one slab avalanche was observed in the Infinity path. This was composed of the most recent storm snow and ran about ½ the distance to the grade. The weather for much of the next ten days was characterized by mostly cloudy skies and periods of light, scattered snow showers alternating with dry and sometimes sunny periods. A few wet loose avalanches ran in Path 1163 and Shed 10 on a sunny afternoon on Jan. 15th. A couple of these reached destructive size 2 (D2). Snow accumulations during this time totaled a measly 2-3” before conditions completely dried out on the 14th. Another arctic front pushed over the Continental Divide from the NE on the 17th ushering in the coldest temperatures of the season. Overnight lows dipped to -15 to -10 °F but soon began to moderate and reached more seasonable values by the 21st. The dry weather continued until the very last day of the month. The snowpack gradually gained strength overall and our region enjoyed some of the safest avalanche conditions in recent memory. But, due to all the cold and dry weather, the snowpack’s surface was faceting and becoming quite weak. Our concerns for the future began to build as this layer became weaker. Fortunately, a period of warm and sunny weather ensued from Jan. 25th to the 30th. This created surface melt on slopes exposed to the sun and the subsequent refreeze at night formed a crust on the surface of the snowpack. The shady slopes did not build this crust and any snowfall accumulated directly on the weak layer. On Jan. 31st the weather pattern finally changed, and a weak winter storm arrived that afternoon. February 2025: The storm that kicked off February under-produced regarding precipitation. The Program Area received only 6” of snow with 0.50” water on the Canyon floor and 7-10” of new snow above 6000’ by sundown on the 1st. But westerly winds were moderate to strong with gusts exceeding 40 mph in terrain above 5500’. The wind loading was substantial.. An arctic front arrived on the 2nd ushering in colder temperatures and caused winds to clock from SW to the NE. Wind speeds were strong to extreme and a blizzard ensued before conditions calmed down that night. Snowfall began again on the 3rd and continued for the next 48 hours. By sundown on the 5th, the Canyon floor received 5-7” of new snow with 0.50” of water. Elevations above 6000’ picked up another 8-10” of snowfall. Another push of arctic air arrived on the night of the 4th/5th and the Canyon was subject to strong NE winds and severe blowing and drifting snow. The weather had cleared by the morning of the 5th and a recent slab avalanche was observed in the Infinity path. It was D2 in size and ran about 1000 vertical feet, or ½ the distance to the grade. After a day and half of benign weather. Clear sunny weather on the 7th revealed an avalanche that had run in Path 1163, most likely on the night of the 5th. This was also a D2 and ran about ¾ distance to the rail. The Program Area experienced only light snowfall with seasonable temperatures before yet another arctic airmass arrived on the 10th. This time conditions remained dry, but very cold, with overnight lows dipping down to -20 and even -30 °F at some locations. Concerns grew as the slab over the late-Jan. faceted weak layer grew thicker. But observations generally found good stability and there were no additional avalanches observed in the Program Area through Feb 16th. Avalanches outside the Railway terrain in the Flathead Range and Glacier Park were also quite limited. February 15th kicked off a period of extended snowfall. A weak arctic front pushed over the Continental Divide on the 16th and elevated the wind speeds created heavy blowing and drifting snow. By morning on the 18th, the Canyon floor had accumulated about 9-10” of snow with 0.40” water. Upper elevations received another 10-14” of snowfall. Observed avalanche activity was limited to D1, loose dry sluffs on steep, rocky slopes in Path 1163 and similar type terrain. The RADS rating fell back to Level 1 on the 18th. A wet atmospheric river from the Pacific impacted the Program Area beginning on the night of Feb. 22nd. Freezing levels climbed and it was raining up to 5500’. A small wet loose avalanche ran in the Umbrella path putting 1-2’ of debris onto Main 1. The precipitation intensified overnight and by late-morning the Canyon had picked up 0.50” of rain. A couple D2 wet loose avalanches ran in Shed 12 with at least one event putting a couple feet of debris onto the shed roof. Two D1.5 wet loose avalanches ran above Hwy 2 in Blue Rock East with 3-4’ tall debris piles terminating on the white line of the east bound lane. A D2 wet loose ran in the Burnout avalanche path. The associated debris was 3-5’ deep and 20-30’ wide and conveniently terminated on top of the old retaining wall. The forecast called for heavier precipitation over the next 24 hours. The storm became even stronger overnight and by sunrise on the 24th it had dumped another 1.00” of water with more than foot of snow above 6000’ in just 6 hours. Westerly winds increased as well, and a widespread avalanche cycle ensued. Slab avalanches ran in Shed 8, Shed 10, and Infinity. But the most impressive avalanche occurred in Path 1163. It was D3 in size and reached 85% distance to the rail with debris piles 20-30’ deep. D2 avalanches reached about 75% distance to the highway in Larry and Curly and there were many other large to very large (a couple nearing D4 size) in terrain outside of, but adjacent to the Program Area. There were no additional avalanches observed over the next 24 hours. An impressive ridge of high pressure parked itself over much of the western U.S. around Feb. 27th resulting in sunny skies and above-average temperatures. The Program Area saw daytime highs nearing 60°F on the Canyon floor and 50°F was recorded at the Snowslip weather station up at 7000’ elevation. Another wet loose avalanche cycle ensued with D2 slides in Path 1163, Shed 10, Shed 9, and I Beam. All debris terminated well above the rail and highway. Snow depths thinned rapidly below 5000’ and some paths such as Jakes and Umbrella almost completely melted out. March 2025: From March 2nd through the 10th the weather was mostly mild with above-freezing temperatures below 5500’. The snowpack below this elevation continued to melt out and by the 14th avalanche paths such as Second Slide and the Shed 4D Cutbank were mostly snow free and Burnout was starting to break up into disconnected patches of snow. But above 6000’ the snowpack continued to grow. The second week of March was mostly wet with a series of small storms that brought light precipitation each day. Another atmospheric river arrived on the 15th. This one was a bit cooler than the February event and the Canyon floor received 6-8” of snow and about 0.75” of water. Terrain above 6000’ picked up over a foot of new snow and received the brunt of some strong SW winds with gusts exceeding 40 mph. Due to the lack of snow in the lower reaches of the railway avalanche terrain. the RADS rating remained at Level 1. No avalanches were observed in the Railway terrain after the weather cleared on the 17th, but some D2 soft slabs were observed on nearby Elk Mountain. After a brief dry spell through the 19th, snowfall returned with another 6-8” of snow on the 20th and 21st. On the 22nd the wettest winter storm of the season hit the Program Area. By nightfall the Canyon floor received just over a foot of snow and terrain above 6000’ picked up over 2’. Conditions began to warm late on the 23rd and heavy rain began around sundown. Rain poured through the night and all the next day. By the end of the day on the 24th a widespread avalanche cycle had ensued with a mix of hard slabs, soft slabs, and wet loose events above the rail. Most impressive was a D2.5 hard slab in Path 1163 with debris that terminated ¾ distance to the grade. Multiple other D2s ran in the Railway terrain but all associated debris remained above the rail. By the morning of the 25th, the Canyon floor had received almost 3.00” of rain over past 48 hours and freezing levels had climbed to 8000’. Temperatures warmed even more on the 26th as skies cleared under a brief high-pressure ridge. Daytime highs reached 65 °F on the Canyon floor and 52°F at the Snowslip weather station at 7000’. Despite the soaring temperatures, no new avalanches were observed. The snowpack appeared to be adjusting to the heat and melting conditions and with cooler weather on the way. Another D2 wet slab ran in Shed 7 West sometime on the 26th or 27th with debris terminating at ½ path. Avalanche activity ceased once sub-freezing temperatures returned on March 29th and the month finished with mostly cloudy and seasonable weather. April 2025: April began with a couple inches of new snowfall above 6000’ and a trace to 1” on the Canyon floor. A more potent system arrived late on the 2nd and continued through the 3rd and the Program Area accumulated a few more inches of new snow. A high-pressure ridge moved in immediately following the storm and the skies cleared, and temperatures climbed. The warm and sunny weather prevailed for much of the time until the season concluded on April 15th. No other avalanches were observed. |
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| 2023-11-01 | 2024-04-15 | Clark | Pre-Season and December 2023: Sunny, warm, and mostly dry weather lasted in NW Montana until October 24th when an Arctic front arrived and temperatures plummeted as low as -5° F. This is when the first snowfall of the season occurred as well. The Canyon floor received 2-4” of snow and elevations above 6000’ accumulated 6-10”. The remainder of October was dry and cold with overnight lows dipping well below 0° F. Winds were consistent out of the NE. Early November saw a gradual warming trend back to more seasonable temperatures. An atmospheric river arrived on November 2nd and lasted for several days. This brought heavy precipitation, most of which fell as rain in the Program Area as freezing levels climbed to over 8000’. Colder weather on November 6th brought the freezing levels back to about 5000’ and a series of wet systems over the next couple days delivered 4-6” of snow and just over an inch of precipitation. High pressure set in on November 9th with dry weather until the 15th when the first potent winter storm of the season put about a foot of new snow on the ground above 6000’ and 1.00-1.30” of rain on the Canyon floor. Another ridge of high pressure built over the region on the 16th with only weak pulses of moisture causing scattered snow showers for the next few days. The ridge strengthened on the 25th and dry weather ensued until the end of the month. Snow depths on the Canyon floor ranged from 0-3” and stations above 6000’ were reporting 15-18”. Slopes with sunny aspects were largely snow free until about 6000’. No avalanches were observed. The late November dry period had degraded snow cohesion properties (facet layer) faceted much of the snow and created the first concerning weak layer of the season. On December 5th a storm finally arrived, but it was quite warm and freezing levels soared up to at least 8000’. Instead of accumulating snow, the Program Area lost snow until colder weather arrived on the 7th and formed a thick crust on the surface of the snowpack at all elevations. The November facet layer was largely destroyed and no longer much of a concern. Subsequent snowfall buried this crust with another 6-10” of snow by the 14th when another ridge of high pressure set in on the 17th. Warming temperatures once again diminished snowpack depths, and by the 21st, much of the avalanche terrain above the rail was melted out. Sub-freezing temperatures returned on the 22nd and another crust capped whatever snowpack remained at all elevations. On the 23rd a weak storm deposited 2-3” of snow on top of the December 22nd crust at Canyon floor elevations and 5-10” above 6000’. On the 24th, yet another strong ridge of high pressure built over the region ushering in dry sunny weather and warming temperatures. On the 30th freezing levels rose to near 10,000’ elevation with calm winds and sunny skies. January 2024: January 1st broke records for the least amount of snow on the Canyon floor on that date. Snow depths here ranged from 3-7”. Averages for this time of year range from 19-24”. Colder weather arrived around New Year’s and with it, an inch or two of snow. The cold temperatures combined with a shallow snowpack created a layer depth hoar at the ground below about 5500’. It also created a later of near surface facets on top of the late-December crust above this elevation. Consistent snowfall increased snow depths and by the end of the first week of the month, terrain above 6000’ had 2-4’ of snow on the ground. A winter storm arrived on the 9th and lasted through the 11th. An Arctic front arrived on the 10th and severe easterly winds created blizzard conditions. Following the storm, the Canyon floor had gained 10-14” of snow with about 1.00” of water. Elevations above 6000’ picked up 15-20” of snow. There were finally some avalanches with a few small Destructive Size 1 of 5 (D1) slabs observed in Shed 6 and on steep cutbanks above the highway and the river. . More notable was several D1 and a few D2 size crowns in Path 1163 and the uppermost reaches of Shed 10. A larger, D2.5 hard slab failed in Shed 9 on the facets resting on top of the late-December crust. All debris terminated well above the rail grade. A frigid Arctic airmass settled in for the next several days. Overnight lows from January 12-16th were generally -40 to -30 °F with Devil Creek recording -50° F on one particularly cold night. Another winter storm arrived on January 17th. This storm one was more potent than the previous week and prompted a rise in the RADS rating to Level 2 (see table below). Snowfall rates were impressive, measuring at 1-2” per hour at times until around 0100 on the 18th when the precipitation died off. This storm was also an overrunning event with moisture from the Pacific riding over cold Arctic air trapped below in the bottom of the Canyon. Storm totals amounted to 13-17” on the Canyon floor with 0.70-0.90” of water and about 20” in the terrain above 6000’. Easterly winds were again severe creating whiteout and blizzard conditions. A notable avalanche cycle ensued during the storm with a couple D2 size slab avalanches in Path 1163 and Shed 7 West. There were smaller, D1 size crowns basically on any slope nearing 35°. All debris terminated well above the grade. . The cold and snowy weather did not last long as a wet and warm front arrived on the 19th. For much of the next week light rain occurred on the Canyon floor and the freezing levels hovered around 5500-6000’. Several small (D1) wet loose avalanches ran during this time as well as a few small (D1) wet slabs on steep cut banks above the rail, highway, and river. On the 28th a more substantial warm up occurred with freezing levels climbing to over 7000’ with rain. The skies cleared on the 29th and several large (D2-D3) hard slab avalanches had failed in the Goat Lick, Hanging Tree, and I Beam avalanche paths. The crowns spanned several hundred feet, but debris terminated well above the highway. An investigation of a couple crowns in I Beam revealed that these avalanches failed on the layer of facets resting on top of the late December crust. There were also a couple D2 size wet loose avalanches in Path 1163 and a D2 size wet loose slide in the Shed 10 Feeder. Debris terminated above the rail. The weather kept getting warmer and January ended with daytime high temperatures nearing 50° F at elevations over 6000’. Locations just east of the Continental Divide such as St. Mary and East Glacier reached 60°F. February 2024: Like the previous month, February 1st was record-breaking for the lowest snow depth recorded on the Canyon floor. Values ranged from 8” at Devil Creek to 14” at Essex. Averages for this time of year range from 25-32”. Sub-freezing temperatures finally returned on Feb. 3rd as the weather pattern became more seasonable with scattered snow showers that deposited 3-5” of snow on top of the new Feb. 3rd melt-freeze crust. The thin layer of new snow on top of this crust quickly faceted and became the next weak layer of concern in our snowpack. A period of consistently snowy weather began on Feb. 8th and the mountain snowpack finally began to grow in steady increments. The wet weather was interrupted by a brief drying and cooling period with the arrival of an Arctic airmass on Feb. 13-16th followed by a sunny high-pressure period during the 17-19th. By now the weak layer of faceted snow on top of the Feb. 3rd crust was buried by 1-3’ of cohesive snow and became reactive. On Feb. 18th there were several skier-triggered avalanches in the nearby Flathead Range. In one instance a rider was caught, carried, and injured and required a helicopter evacuation. The following day another skier was caught in the same basin but escaped uninjured. No avalanches were observed above the rail at this time. Wetter weather ensured beginning Feb. 20th as a series of warm storms impacted the Program Area. The snowpack above 6000’ increased by another 1-3 feet, but the Canyon floor depths remained well below average due to receiving rain instead of snow. A potent storm on the 25th/26th produced 1.20” of water on the Canyon floor and about a foot of snow above the freezing line which hovered around 5000’. Feb. 28th brought another warm and very windy storm. By sunrise on the 29th elevations above 6000’ had received well over a foot of new snow and more than 0.50” water overnight combined with severe loading from strong to extreme SW winds. A widespread avalanche cycle ensued with D2.5 hard slab avalanches in Path 1163 and Shed 7 West. Debris from these two events ran about ¾ path in 1163 and 2/3-path in Shed 7 W terminating above the rail. In the nearby Flathead Range multiple D2-D3 avalanches were observed with some crowns running over 1500’ in width. The failure layer for these large hard slab avalanches was most likely the facets resting on top of the Feb. 3rd crust. Due to the abnormally thin snow depths below 6000’ the RADS rating remained at Level 1 (see table above) throughout the month. The lack of snow combined with high surface roughness in the avalanche paths kept the avalanche hazard at the rail grade low. March 2024: February snowfall grew the seasonal snowpack above 6000’ to more typical depths, but not enough to reach long-term averages. Meanwhile, snow depths on the Canyon floor continued to break records measuring at a measly 15-21” compared to 30-40” which is typical for this time of year. March 1st snow depths were the lowest recorded since 2006 at Essex and Devil Creek. There have been other similar winters with shallow March snow depths such as in 2009-10, 2014-15, and 2015-16 when conditions were like this year. At Java East, the 2009-10 and 2015-16 seasons had less snow on the ground on March 1st by 2”. A weak Arctic front arrived from the NE on March 1st and quick pulses of moisture overran this and the Program Area picked up 2-6” of additional snow by the 5th with the east end favored. A drying and warming trend ensued from March 6-9th with daytime highs reaching 50 °F on the Canyon floor and the low-40s °F above 6000’. The next five days were mostly unsettled with weak pulses of moisture that brought another 0.50” of water and 6-8” of snow. Beginning March 14th an impressive ridge of high pressure moved into the region. The skies cleared and temperatures climbed each successive day. Daytime high temperatures peaked around the 19th with values reaching 50 °F at 6500’ and freezing levels soaring to over 10,000’. There was a widespread avalanche cycle across the region on all sun-exposed slopes. However, due to the lack of snow and minimal avalanche activity specifically in the railway terrain. Avalanches above the rail were mostly limited to a few D1 wet loose sluffs. But of note there was one impressive D2.5 wet slab that ran in Path 1163 on the 18th with debris terminating ¾ path. Cooler weather arrived from the NE on the 21st and temperatures dropped below freezing at all elevations. Terrain at elevations above 6000’ received another 12-20” of snow over the next four days. The weather slowly warmed beginning the 25th but remained unsettled for the remainder of the month with brief sunny and warm periods alternating with cloudy days that brought scattered showers. Overall, the snowpack continued to settle and stabilize at elevations above 5500’ and pretty much melted out in the railway terrain below this elevation. April 2024: April began warm and sunny with daytime high temperatures reaching 60 °F on the Canyon floor and freezing levels climbing above 9000’. The snowpack continued to melt with losses now occurring at all elevations. Low to mid-elevation avalanche paths such as Second Slide, Jakes, and Burnout were largely free of snow by the end of the first week. A cold front arrived on the 3rd bringing with it increasing clouds, light precipitation, and freezing levels lowering to 5000’. The Canyon floor picked up 0.20” of rain and terrain above the rain/snow line had 2” of fresh snow by the morning of the 4th. The weather continued in a typical spring-like fashion with a mix of below-freezing conditions and snowfall alternating with sunny periods and above-freezing temperatures. Avalanche activity was limited to a few D1 loose snow sluffs with debris that terminated well above the grade. A very warm and dry period began on the 10th and lasted for five days. Daytime high air temperatures peaked on the 14th, reaching 70 °F on the Canyon floor and the mid-50s °F at 7000’. Most of the snowpack below 6000’ melted out in the Railway’s avalanche terrain. Cooler and cloudier weather arrived on the 15th when the 2023-24 season ended. |
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| 2023-01-01 | 2023-01-31 | Clark | The first two weeks of January were characterized by mostly dry and benign weather. Snow depths gained very slowly as weak pulses of moisture would drop an inch or two every few days. Observations noted facets forming on top of the December 28th crust. But then a warm-up occurred beginning on the 10th and lasted until the 14th when sub-freezing temperatures returned. A new crust formed on the snowpack’s surface that extended up to 7000’ elevation. Avalanche activity during the warm weather was limited to small wet loose avalanches (D1s) and some cornice fall in Shed 7 West. No debris reached the rail. The second half of January was even drier than the first. A mere 3.5” inches of total snowfall were recorded in Essex between January 10th and 26th. A winter storm dumped feet of snow to the south of the Program Area on the 27th, but snowfall totals were limited to 2-3” on the Canyon floor and 4-6” above 6000’ by the 28th as the moisture feed stayed south. Cold arctic air infiltrated the Program Area overnight on the 27th/28th and temperatures plummeted to below zero/single digits °F. Two D2-size avalanches ran on the 28th, one in Path 1163 with debris terminating 2/3rd distance to the rail, and one in the Shed 10 Feeder path with debris terminating well above the rail. Both were soft slabs likely formed/triggered by recent winds. January finished cold and quiet with limited snowfall as the Arctic air slowly moderated. Over the month of January BNSF Avalanche Safety issued a total of five (5) ACRs on the following dates: January 6th, 10th, 20th, 26th, 31st. The mean matrix score for the month was 36 with a minimum value of 30 on Jan. 6th and 10th and a maximum value of 48 on Jan. 48th. It was an exceptionally dry month with only about a foot of total snowfall measured on the Canyon Floor. |
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| 2022-12-01 | 2022-12-31 | Clark | The first Avalanche Conditions Report (ACR) was issued on November 30th with a Matrix score of 18 as a winter storm hit the Program Area. Another storm on December 2nd deposited another 15-22” of snow prompting a rise in the Matrix Score to 48, the upper end of RADS Level 1. Snow depths at upper elevations were now well above average and nearing 4’ deep. No avalanches were observed in the Railway terrain, but several were in the nearby Flathead Range with one Destructive-size 3 of 5 (D3) on the SE face of Snowshed Mountain that failed on the November facets and appeared to have ran full path down to Sheep Creek. A potent winter storm slammed into the Program Area on December 20th. This was a classic overrunning event with Pacific moisture riding over a brutally cold Arctic airmass pushing in from the NE. The RADS was elevated to Level 2 and three D2.5 size avalanches were observed in three separate paths, Shed 7 West, Shed 10, and Path 1163 on the 21st. These avalanches in Shed 7 and Shed 10 were later found to have failed on the November facets with associated debris breaking many trees. A thin ribbon of debris ran to within 50’ of the shed roof in Shed 7 and the Shed 10 slide ran to 4500’ elevation. A couple D1 wind slabs put some debris on the inside Main at some cut banks east of Blacktail. The Canyon floor picked up 22” of snow with 1.00” of snow water equivalent during the December 20th/21st storm. High elevation weather stations reported storm totals between 19-24”. The following three days were bitterly cold with Marias Pass recording a low of -49 °F on the 22nd. The RADS remained at Level 2 until the evening of December 24th when it was elevated to Level 3 due to rapidly warming temperatures and rain. Freezing levels and rain extended up to at least 7800’ during the following days (December 25th-27th) and Java East recorded 2.50” of rainfall. A widespread avalanche cycle ensued with many D2-D3 size avalanches in the Program Area and surrounding region. Notable activity included a D2.5 slab avalanche triggered by a falling cornice that ran 2/3rd-distance to the rail in Shed 7 West and three D2s running ¾-distance to the rail in Path 1163. On the 27th another D2.5 wet loose avalanche ran in Path 1163 with debris gouging down to the November facets near the ground and terminating ¾ distance to the grade. Several wet loose/wet slab avalanches, size D1-2 ran in the Blue Rock Cut and Blue Rock East above Hwy 2 with four slides blocking the eastbound lane around 0200 hours on the 27th. Sub-freezing temperatures returned on the 28th and the RADS was downgraded to Level 2 and then down to Level 1 on the 29th. Avalanche debris reaching the rail was limited to a couple D1 wet loose slides in the Shed 4D Cutbank and other similar short, but steep slopes adjacent to the rail. Over the month of December, ten (10) ACRs were issued on the following dates: December 2nd, 6th, 14th, 19th, 20th, 21st, 24th, 26th, 28th, and 29th. The mean matrix score for the month was 59, the minimum was 18 on the 2nd, and the maximum was 89 on the 26th. |
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| 2022-10-01 | 2022-11-30 | Clark | Pre-Season and December 2022: Unseasonably warm and dry weather lasted in NW Montana until the 4th week of October with temperatures well above average and persistent wildfire smoke filling the air. The pattern abruptly changed with the first major snowfall of the season on October 21st-23rd when 2-3” of snow fell above 5000’ and 6-8” accumulated above 6000’. Snowfall continued through the 25th with another 4-6” at upper elevations. After a dry week, a series of storms deposited another 10-20” of snow in the high country between Halloween and November 6th. The first Arctic front of the season arrived late on the 6th and temperatures plummeted below 0 °F for several days with NE winds. Dry and mostly cold conditions continued until November 22nd and much of the snowpack faceted creating a nasty weak layer that became a concern the following month. This layer was buried on November 23rd and a few weak pulses of moisture continued to grow the mountain snowpack so that depths above 6000’ were exceeding 2 feet by the end of the month. |
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| 2021-04-01 | 2021-04-15 | Clark | BNSF Avalanche Safety issued a total of two (2) ACRs during the month of April on the following dates: April 9th and 15th. The RADS rating never rose above Level 1 and the mean matrix score for the month was 15 with a maximum value of 18 on the 9th and a minimum value of 12 on the 15th. By April 1st much of the snowpack below 5500’ had melted away and the snow above that elevation was mostly stable. No additional avalanche activity was observed in the Program Area during April and the 2020-21 season ended quietly on the 15th. | |
| 2021-03-01 | 2021-03-31 | Clark | BNSF Avalanche Safety issued a total of five (5) ACRs during the month of March on the following dates: March 3rd, 7th, 15th, 23rd, and 31st. The mean matrix score was 43 with a maximum value of 74 on March 3rd and a minimum value of 25 on the 31st. March began with a rapid warm-up and near record high temperatures. This very fast transition to spring-like weather initially caused a period of increasing avalanche danger where the matrix score was increased to the upper reaches of Level 2, but not enough to reach Level 3. Fortunately, no more avalanches reached the railway during the first week of the month, but a very impressive slab avalanche ran in a path known as I-Beam which threatens US Highway 2, but not the railway. This slide ran about ¾ path, stopping short of the highway. The only avalanche activity observed in terrain threatening the rail were small wet loose avalanches that terminated well above the grade. Daytime highs during this period reached 60°F on the Canyon floor and into the 40s°F above 6000 feet elevation. Overnight lows were inverted with values in the teens-20s °F on the Canyon floor but only dropping into the high-30s °F at ridgetop locations. The RADS rating was finally lowered to Level 1 on March 7th. The next week saw more seasonable temperatures with sub-freezing overnight lows at all locations and near-freezing or above-freezing temperatures during the day. This prolonged period of melt-freeze conditions helped to stabilize the snowpack and continued the fast melt-out of snow below 5500 feet elevation. The last two weeks of the month finished with benign weather and very limited avalanche activity consisting of very small wet loose sluffs that did not reach the rail grade. |
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| 2021-02-01 | 2021-02-28 | Clark | BNSF Avalanche Safety issued a total of twelve (12) ACRs during the month of February on the following dates: February 3rd, 6th, 7th, 11th, 21st, 22nd (x2), 23rd (x2), 24th, 25th, and 28th. The mean matrix score for the month was 67 with a minimum value of 27 on the 3rd and a maximum value of 105 on afternoon of the 23rd after a large-magnitude avalanche ran in Shed 7 West. The first week of February was wet as several potent Pacific storms impacting the region. Settled snow depths quickly increased by 1-3 feet across the Program Area. Some impressive avalanche activity was observed on Feb. 5th in the nearby Shields Creek basin, located adjacent to the Shed 7 path, but in terrain that does not threaten the rail. One of these was a large-magnitude D3-size avalanche located on the east face of Snowslip Mountain that appeared to be naturally triggered by heavy wind-loading. The RADS rating rose to Level 2 during February 5-7th due to heavy snowfall and elevated winds. On the 6th a very cold Arctic airmass spilled over the Continental Divide and settled over NW Montana. Over the next week overnight low temperatures plummeted as low as -30° F and winds clocked to the NE blowing at moderate speeds with strong gusts. Avalanche activity above the rail was limited to small, destructive sized 1-1.5 loose snow sluffs. However, one D-size 2.5 slab released in the Grizzly Gulch in terrain that does not threaten the railway but is located very near the grade. Other notable avalanche activity in the vicinity included the east face of nearby Java Mountain, two separate D2-sized avalanches on the west face of Running Rabbit Mountain, and a human-triggered, D3-size avalanche on the Devil’s Hump south of the Program Area. A relatively warm storm arrived on the 21st beginning with high westerly winds but very little snowfall. At 2030 hours a slide fence indication was reported in the Second Slide avalanche path (MP 1162.5). Shortly after, a west-bound and now stopped train on Main 1 confirmed that the indication was caused by avalanche debris that had hit the fence and buried Main 1. The RADS rating was elevated to Level 4 that night as snowfall rates increased, and the winds remained elevated. No additional avalanche activity was observed above the rail for the next 12 hours and the RADS rating was cautiously dropped to Level 3 at 1150 hours on the 22nd. Later that afternoon a D2-sized slab avalanche ran in the Java Gauntlet, but the associated debris stopped short of the rail. By the morning of the 23rd precipitation rates, wind speeds, and temperatures were dropping and only one other avalanche had been observed in Path 1163 with debris running only 2/3rd path. However, at 1100 hours a very large, D3-sized avalanche ran in the Shed 7 West path. Associated debris ran over shed with a massive powder cloud (see photo below) and caused extensive vegetation damage in the vicinity. After the Shed 7 avalanche, the RADS rating was increased again to Level 4 and plans were finalized that evening to conduct an avalanche control mission utilizing a helicopter to deploy explosives into several avalanche paths located in the railway Program Area. The RADS rating was lowered to Level 3 shortly after the mission on the 24th and then further lowered to Level 2 the following morning. The weather remained active for the rest of the month with continued snowfall and elevated winds. This combined with lingering concerns about the mid-January weak layer kept the RADS rating at Level 2 for the remainder of the month. |
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| 2021-01-01 | 2021-01-31 | Clark | Throughout January BNSF Avalanche Safety issued a total of 6 ACRs on the following dates: January 3rd, 12th, 13th (x2), 18th, and the 28th. The RADS rating rose to Level 2 on the morning of the 13th due to rapidly warming temperatures and rising freezing levels. But a fast-moving cold front soon dropped the rating back to Level 1 by 1700 that evening. Much of the remaining month was dry with very little snow and the avalanche danger remained at Level 1. The mean matrix score for the month was 35 with a minimum value of 20 on the 18th and a maximum value of 59 at 0823 hours on the 13th. The first half of January was characterized by a few warm winter storms that brought mostly rain to elevations below 5500’ and snow above that. On Jan 12th/13th a more potent and exceptionally warm storm impacted the Program Area. Freezing levels soared up to 7000’ and almost 1.5” of rain fell. The RADS rating was elevated to Level 2 as several destructive sized 1-2 wet loose avalanches were triggered in terrain above the rail with debris running 2/3rd to ¾ path but stopping short of the grade. One notable slab avalanche (D2-size) ran in Path 1163 with debris terminating about ¾ path. By sunset on the 13th a cold front moved into the region and quickly dropped air temperatures back below freezing. A stout melt-freeze crust formed on the surface of the snowpack, effectively locking down the snow and the RADS rating was lowered back to Level 1. The “Jan. 13th Crust” as it was named, was widespread across the Program Area and most of the surrounding region. Also notable during this time were the extreme winds. Gusts ranging between 40-60+ miles per hour were common, and in a couple high elevation locations exceeded 100 miles per hour. For two weeks after January 13th the weather was often dry with only a couple very light snowstorms. The avalanche danger decreased along with the Matrix score. However, what little snow fell on top of the Jan. 13th crust began to facet and weaken under substantial temperature gradients. By the end of the month there was a widespread weak layer of faceted snow resting on top of the firm and slick Jan. 13th crust. This set the stage for the large-magnitude avalanches that occurred the following month. On January 28th the cycle of dry weather broke and series of storms over the next three weeks began to build a substantial slab of snow over the mid-January weak layer. |
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| 2020-12-01 | 2020-12-31 | Clark | Over the month of December BNSF Avalanche Safety issued a total of four (4) ACRs on the following dates: December 2nd, 12th, 19th, and the 27th. The RADS rating never rose above Level 1. The mean matrix score for the month was 12 with a minimum value of 5 on Dec. 12th and a maximum value of 20 on Dec. 27th. An impressive ridge of high pressure parked itself over the Program Area from December 1st through the 8th. This brought dry, stable weather with inverted air temperatures where cold, sub-freezing conditions prevailed on the Canyon floor and warmer air existed aloft above 6000 feet. On the 8th a warm front arrived and daytime air temperatures soared to well-above freezing at all elevations. The high in Essex that day was 55 °F and weather stations above 6000 feet reported daytime highs in the 40s °F. A cold front moved in on the 9th and quickly formed the widespread December 9th melt-freeze crust on the snowpack surface throughout the Program Area. Afterwards a series of small storms incrementally built up the snowpack and by the 19th a foot or more of snow had accumulated on the crust. Thin layers of weak faceted snow formed around this crust creating the first notable persistent weak layers of the season. A notable warm-up occurred on the 22nd when above freezing temperatures rose to near 6500 feet elevation. This was also accompanied by some light rain and triggered multiple slab avalanches outside the Program Area in the nearby Flathead Range. Several Destructive Size 2 and even a few Destructive size 3 avalanches were observed. The Program Area was spared and no avalanches were observed in the terrain above the rail. Several small storms incrementally buried the December 22nd crust with about a foot of snow by the 27th. Again, some thin layers of weak, faceted snow formed around this crust, forming another notable persistent weak layer within the snowpack. A large glide avalanche (Destructive size 3) ran on the southeast face of nearby Snowshed Mountain. This avalanche was outside of the Program Area and did not threaten the railway. But it was notable for its size and the fact that glide avalanches failing in December are rare. From the starting zone at 7000 feet, it appeared the associated debris may have run full path, a vertical drop of almost 3000 feet. 2020 ended with no notable avalanche activity observed or reported within the Program Area save for few very small (Destructive size 1) wet loose sluffs on steep, low elevation cut banks such as Umbrella Fence. |
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| 2020-10-01 | 2020-11-30 | Clark | Dry and warm, summer-like conditions prevailed in the Program Area until about October 10th when the weather pattern finally broke and a period of cold and snowy weather enveloped the region. By October 20th there was well over a foot or two of snow in much of terrain above 6000 feet. Immediately following this there was a weeklong cold snap with overnight low temperatures dropping below zero °F in the mountains. However, during the last few days of October and the first week of November temperatures rebounded to above normal and the mountain snowpack began to melt and lost almost half its depth. Colder temperatures and a couple potent storms once again brought accumulating snow to the high country during the second week of November. After another brief lull during the 3rd week of the month, November finished with a series of small storms that built up the snowpack in small increments. During the last week of the month daytime highs sometimes reached above freezing then dropped below freezing at night. This created a snowpack structure characterized by several melt-freeze crusts interspersed with partially melted and re-frozen grains. By the start of December there was 2-4 feet of snow above 6000 feet in the Program Area and about a foot of snow on the Canyon floor. These were above-average snow depths for that time of year. BNSF Avalanche Safety issued the first ACR of the 2020-21 season on November 25th with a RADS rating at Level 1 and a matrix score of 11. |
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| 2020-04-01 | 2020-04-30 | Clark | BNSF Avalanche Safety issued a total of three (3) ACRs during the month of April on the following dates: 4/4, 4/10, and 4/15. The mean matrix score for the month was 37 with a minimum value of 25 on the 15th and a maximum value of 45 on the 4th. Winter-like conditions returned in force during the first few days of April. By the end of the first week another 1-2 feet of new snow had accumulated in terrain above 6000 feet. Very little avalanche activity was observed in the Program Area, but in the nearby Flathead Range several large, Destructive size 2 and size 3 slab avalanches had failed on the March 24th crust and faceted weak layer. In some instances these avalanches were unintentionally triggered by parties of backcountry skiers and resulted in a couple of close calls. A period of high pressure with abundant sunshine and steadily warming temperatures ensued from the 7th through the 10th. Daytime highs reached 60° F on the Canyon floor and neared 50 °F above 6000 feet. This led to a widespread wet loose avalanche cycle on slopes with easterly, southerly, and westerly aspects as the snow from late March and early April slid on the March 24th crust. Most of these avalanches were small in size, Destructive size 1s and 1.5s, but a few Destructive size 2 (could bury, injure, kill a person) wet loose slides ran in Shed 11, Path 1163, and Shed 10. Only a couple small, D1 slab avalanches were observed in the Program Area during this avalanche cycle. All avalanche debris terminated well above the rail grade. Several large slab avalanches were observed outside the Program Area in the nearby Flathead Range during this same time, many of which appeared to be running on the March 24th crust and faceted weak layer. The warm sunny weather came to an abrupt halt on the night of the 10th as another Arctic front from the northeast moved in. Temperatures dropped into the high-20s °F on the Canyon floor and the teens °F above 6000 feet and the snowpack surface was capped by a thick melt-freeze crust that greatly improved stability. A forecasted winter storm for the 11th was a bust with only a trace to four inches of new snow accumulating across the Program Area. Cool and mostly cloudy weather prevailed for the next several days and the 2019-20 season finished quietly on the 15th of April with no additional avalanche activity. |
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| 2020-03-01 | 2020-03-31 | Clark | BNSF Avalanche Safety issued a total of five (5) ACRs during the month of March on the following dates: 3/4, 3/11, 3/17, 3/24, and 3/31. The mean matrix score for the month was 35 with a minimum value of 30 on the 17th and a maximum value of 41 on the 11th and the RADS rating never rose above Level 1. The first ten days of March consisted of mostly benign weather involving very little new snow, temperatures around freezing, and a general stabilizing trend of the snowpack. More active weather returned on the 10th and by the 11th over a foot of new snow had fallen above 6000 feet and 4-9 inches had accumulated on the Canyon floor. Temperatures were just above freezing at the rail grade on the 11th and a small wet loose avalanche ran near the Umbrella Fence putting 2-4 feet of debris next to Main 1 that was about 20 feet wide. A powerful Arctic front impacted the Program Area and much of western Montana from the 13th through about the 14th. Snowfall was limited but strong NE winds formed some thin wind slabs on westerly-southerly aspects. In the Flathead Valley there was extensive tree blowdown from these winds. An extended period of high pressure with benign weather and plenty of sunshine accompanied by warm daytime temperatures began on the 15th. Avalanche activity trended downward as snowpack stability improved each passing day. By the 23rd there had been no avalanches observed above the rail for almost a week. The snowpack below 5500 feet began to quickly melt out, especially on slopes in the western half of the Program Area that have a more southerly aspect. Sub-freezing temperatures returned on the 24th and a stout melt-freeze crust formed on the snowpack surface across much of the terrain. For the next seven days the weather remained unseasonably cold with a steady influx of small storms that buried the March 24th crust. A thin layer of weak, faceted snow formed on top of this crust. Rainfall up to about 5500 feet on the 29th wiped out this layer of facets at low elevations. However in terrain above the 3/29 rain line, the facets kept developing and the slab of overlaying snow kept getting thicker. By the end of the month the March 24th crust/facet layer was buried by up to a foot of snow in the mid to upper-elevations. |
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| 2020-02-01 | 2020-02-29 | Clark | BNSF Avalanche Safety issued a total of six (6) ACRs during the month of February on the following dates: 2/2, 2/8, 2/16, 2/20, and 2/25 (x2). The mean matrix score for the month was 39 with a minimum value of 30 on the 20th and a maximum value of 52 on morning the 13th when the Program Area received up to a foot of new snow overnight. Temperatures continued to warm and precipitation fell as rain up to 7500 feet until late afternoon on February 1st. Several Destructive size 1 and 1.5 wet loose avalanches were observed in Path 1163 before a quick moving cold front dropped temperatures back down to seasonable norms during the PM hours. This formed a distinct melt-freeze crust everywhere on the snowpack surface up to about 7500 feet which greatly improved stability. Avalanches were more numerous and larger outside the Program Area in the nearby Flathead Range during the Jan 31st - February 1st warm-up. A very large Destructive Size 3.5 (could destroy a wood-frame house and take out some trees) ran on the NE face of Cameahwait at the head of Essex Creek sometime on the morning of February 1st. The failure layer was the weak snow near the base of the snowpack. There were several other very large avalanches observed on other peaks in the nearby Flathead Range during the same time period. The weather over the next 3 weeks consisted of a more or less constant stream of moisture in the form of steady, albeit small, snowstorms. This kept the matrix score slightly elevated within Level 1 (mid to high-30s). By the 20th the crust formed by the melt/freeze conditions on February 1st was buried 2-3 feet deep above 6000 feet. One local avalanche professional coined the term, “Febru-buried” to describe the steady and incremental, but not necessarily obvious increase in snowpack depths, especially above 6000 feet. Beginning the 20th and lasting till the 23rd a ridge of high pressure settled over western Montana bringing with it some dry weather and much-appreciated sunshine. Another storm hit on the night of the 24th resulting in another foot of snow in the Program Area by the morning of the 25th. This elevated the RADS rating to Level 2 for the daylight hours but limited avalanche activity prompted a reduction back Level 1 on the evening of the 25th. Another ridge of high pressure arrived on the 27th and lasted until the end of the month bringing with it warm and benign weather with sunny skies. A few small, Destructive size 1 and 1.5 wet loose avalanches were observed in Path 1163, Infinity, and several other avalanche paths as temperatures climbed into the 50s °F on the Canyon floor and well-above freezing above 6000 feet. Associated debris did not reach the rail grade or was too small to be concerning. |
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| 2020-01-01 | 2020-01-31 | Clark | Over the month of January BNSF Avalanche Safety issued a total of ten (10) ACRs on the following dates: 1/4, 1/7, 1/8, 1/12, 1/13, 1/14, 1/17, 1/24, 1/29 and 01/31. The RADS rating rose to Level 2 on the 7th for two days, and again on the 12th for three days during periods of stormy weather. For the remainder of the month the RADS rating remained at Level 1. The mean matrix score for the month was 45 with a minimum value of 21 on 1/4 and a maximum value of 67 on 1/13. 2020 began with a winter storm that dumped 6-16 inches of heavy new snow above 4500 feet elevation. This new snowfall accumulated on the weak near-surface facets and surface hoar that formed during the dry weather period between Christmas and New Years Eve. A few avalanches resulted from the storm including a Destructive Size 2 of 5 that ran in Shed 5. Associated debris ran about 800 vertical feet terminating above the rail grade. After a few days of light snow showers an even stronger winter storm impacted the Program Area from the 6th through the afternoon of the 8th. Snowfall totals exceeded 2 feet in the upper elevation starting zones and weather stations on the Canyon floor measured over an inch of snow water equivalent. Two larger sized avalanches (Destructive size 2.5 out of 5) ran in Path 1163 and Shed 7 West. It was not possible to investigate the crowns of these slides, but observations from Highway 2 suggest that the failure layer for the avalanche in 1163 was the weak faceted snow at the base of the snowpack. In Shed 7 West it appeared the failure layer was likely buried surface hoar that formed between Christmas and New Years. Both of these avalanches ran about 2/3rds path with debris terminating about 600 vertical feet above the railway. Beginning January 11th and lasting through the 14th another potent storm buried John F Stevens Canyon with another 12-20 inches of snow. This was the result of warm and moist air from the Pacific overrunning much colder Arctic air flowing south from the Canadian interior. Visibility was limited during this time so very few avalanches were observed but no avalanche debris reached the rail grade. Observations from Shed 11 on the 14th indicated that a Destructive Size 2 of 5 avalanche ran in that path sometime during the storm cycle. Some very large avalanches were observed by staff with the Flathead Avalanche Center outside of the Program Area in the nearby Flathead Range. These avalanches failed on deeply buried persistent weak layers sometime during the January 11th-14th storm cycle and ranged from Destructive size 3-4 of 5. Debris from the largest slide on Nyack Mountain took out large swaths of mature timber as it ran past the historic forest trimline on the valley floor. The remainder of January was characterized by a series of small storms and brief warm periods with melt conditions up to 6000 feet, and very little avalanche activity. However on the 31st temperatures began to climb abruptly as a strong SW flow brought abnormally warm weather and strong winds. |
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| 2019-12-01 | 2019-12-31 | Clark | Over the month of December BNSF Avalanche Safety issued a total of seven (7) ACRs on the following dates: 12/6, 12/8, 12/13, 12/17, 12/20, 12/23, and 12/31. The RADS rating never rose above Level 1. The mean matrix score for the month was 15 with a minimum value of 7 on 12/6 and a maximum value of 20 on 12/31. By early December the layer of faceted snow overlying the crust from mid-November was buried by several inches to a foot or more of snow. Observations from December 2nd in the Shed 7 East avalanche path revealed this weak layer of sugar-like snow lurking 12 inches below the surface. By December 13 it was still present at this location only then it was buried almost 2 feet down. Unfortunately the weather events in November and December created a poor snowpack structure in and around the Program Area and an associated “persistent slab problem” which simply refers to a cohesive slab of snow layered on top of a weaker layer of snow that is much less cohesive and is resistant to strengthening. Outside the Program Area, several large magnitude, life threatening avalanches were observed failing on this crust/facet layer in the nearby Flathead Range as a couple potent storms in December quickly loaded this layer to failure (photo below). Avalanche activity in the Program Area during December was limited to smaller slides (Destructive size 1s and 2s) with the largest occurring in Path 1163 on December 20th during a period of warm and rainy weather. The associated debris in Path 1163 ran about 2/3rds path terminating well above the rail grade. A period of dry and warm weather with sunny skies occurred between Christmas and New Years. On the snowpack surface a layer of near-surface facetted snow formed along with a widespread layer of surface hoar. Below 6000 feet the snowpack warmed enough to melt slightly then formed a melt-freeze crust once below-freezing temperatures returned. The month of December finished with below average snow depths, especially at low-mid elevations (below 5500 feet). The shallow snow helped keep the railway avalanche danger low despite the poor snowpack structure and a couple decent winter storms. There simply was not enough snow to create large avalanches in much of the terrain above the rail. Also there were still many obstacles (trees, brush, rocks) still not buried in the lower half of the avalanche paths, which acted to limit the extent of avalanche debris. |
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| 2019-09-28 | 2019-11-30 | Clark | The first snow of the 2019-20 winter arrived early this year with an impressive storm on September 28th that dumped several feet of snow near the Continental Divide and at points several miles eastward. Locations just east of Glacier National Park reported 3-5 feet of snow during this event. West of the Continental divide at elevations above 6000 ft. accumulations were more modest, but still high for that time of year, totaling 1-2 feet. October 2019 turned out to be the coldest on record for that month in western Montana, largely a result of a few Arctic fronts impacting the region. Snow depths thinned and thickened above 6000 ft. as temperatures swung from well below normal readings to well above freezing during the days between Arctic intrusions. Temperatures were still erratic in November with warm periods when temperatures reached well-above freezing, even at elevations above 7000 ft. alternating with very cold periods when readings dropped to the single digits or even below 0 °F. By mid-November the snowpack in the Program Area above 6000 ft. consisted mostly of crusted old snow at the base of the snowpack formed by the aforementioned freeze/thaw cycles. On top of this crust a few more inches of snow accumulated slowly. But during the intervening dry spells it underwent a process known as faceting where the existing snow grains became progressively more granular (sugar-like) and lacking in cohesion due to the cold and dry weather. |
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| 2019-04-01 | 2019-04-15 | Clark | A total of 3 ACRs were issued during the month of April on the following dates: 4/3, 4/11, 4/15, with the associated matrix ratings of: 18, 15, and 11 respectively. After the big warm up in late March much of the lower elevation terrain was snow free and the remaining snow had stabilized considerably with the cooler, more seasonable weather during the first half of April. There were no avalanches reported in the Program Area during the month and the 2018-19 season concluded on April 15th. | |
| 2019-03-01 | 2019-03-31 | Clark | A total of 10 ACRs were posted during the month of March on the following dates: 3/7, 3/13, 3/18, 3/20, 3/21 (x2), 3/22 (x2), 3/23, and 3/28. Between the 18th and the 22nd a rapid warm-up with above-normal temperatures affected the Program Area which elevated the RADS rating to Level 2, Avalanche Statement, and Level 3, Avalanche Watch (see table below). Outside of this timeframe, the RADS rating remained at Level 1, Unrestricted. There were a few key factors that led to the impressive March 17-22nd avalanche cycle. First, in locations where the snowpack was relatively shallow, about 2-3 feet deep or less, much of the snow grains had lost cohesion and were composed of weak faceted crystals. This was due to multiple weeks of sub or near zero-degree (°F) temperatures during February and early March. When the temperatures began to climb rapidly by the 17th and 18th, this already weak snow lost even more cohesion and strength and was more susceptible to avalanching. It appeared most avalanches during this event initiated as a small point release in the wet snow. But, as these small avalanches gained momentum while moving downhill, they also gained mass by entraining additional weak snow in the path. This process resulted in many avalanches gouging the season’s snowpack all the way to the ground and, in doing so, effectively removing the entire season’s snowpack from the slope. By the time these wet avalanches reached their termination elevation, their size was impressively large. By March 20th daytime temperatures were climbing into the mid-60s °F at the Canyon floor and the 50s °F above 6000 feet elevation which further weakened the snow. In addition, nighttime lows at upper elevations did not drop below freezing for four consecutive nights in a row and this was a major contributor to the widespread wet snow avalanche activity. By the end of the cycle, over 25 Destructive size 2 (could bury or kill a person) were recorded in the Program Area with one just barely reaching the grade in an avalanche path named “Jakes” (MP 1161.89-1162). Three avalanches reached Destructive size 3 (could destroy a wood frame house) including a wet slab in Shed 11 (photo above) and another in Shed 10.7 where the debris terminated within 100 yards of the Shed. Cooler temperatures finally arrived on the 23rd and the avalanche activity largely ceased. The RADS rating was dropped to Level 1, Unrestricted on the evening of the 23rd and remained at that level for the rest of the month. Overall the mean matrix rating for the month was 55 with a minimum value of 20 on the 28th and a maximum value of 88 on the afternoon of the 22nd. |
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| 2019-02-01 | 2019-02-28 | Clark | BNSF Avalanche Safety issued a total of 12 ACRs during the month of February on the following dates: 2/1, 2/3, 2/5, 2/9, 2/12, 2/13 (x2), 2/14, 2/15, 2/19, 2/25, 2/28. The mean matrix rating for the month was 47 with a minimum value of 27 on the 28th and a maximum value of 93 on the 13th when the Program Area went through a brief avalanche cycle following a potent winter storm. February began with a warm up on the 1st and 2nd with above-freezing temperatures and rain extending up to 6500 feet elevation. Numerous very small wet loose avalanches ran during this time including one reaching the grade at Umbrella Fence. The associated debris was only about 3 feet deep and 10 feet wide and went unreported at the time. An Arctic front pushed over the Continental Divide on the 3rd and temperatures dropped 30 to 40 degrees (°F) with an increase in northeasterly winds. Snowfall amounts weren’t impressive but the amount of wind-loading was enough to create wind slabs that failed and avalanched on some slopes. One example was the Infinity path where a Destructive Size 2 avalanche ran 2/3rds path sometime on the 5th. Sub-zero temperatures and NE winds persisted until about February 12th when a strong winter storm impacted the Program Area. This storm began cold and deposited several inches of fluffy, low-density snow. As temperatures warmed the snowfall became progressively denser and began to slowly form into a more cohesive slab. The RADS rating was increased to Level 2, Avalanche Statement on the afternoon of the 12th (table above). The next day on the 13th numerous naturally triggered slab avalanches had failed as a result of the storm and the creation of an upside-down snowpack where heavier, more dense snow (the slab) overlaid less dense and weaker snow beneath. Avalanche activity occurred above the rail and US Highway 2 with debris reaching both the rail and the highway. Most notable was debris 4-8 feet deep from the Shed 4D/Burnout Cutbank which covered Main 1 for about 200 linear feet (photo below). The RADS was elevated to Level 3, Avalanche Watch at 0930 on the 13th. Due to the existing snowpack conditions and observed avalanche activity BNSF Railway management applied for a Special Use Permit from Glacier National Park on the 13th. On the 14th the weather had cleared and at about 1200 Two Bear Air flew with the Daisy Bell® for a short mission in the east end of the Program Area. Results from the mission resulted in minimal avalanching and the mission terminated and the RADS rating was lowered to Level 2, Avalanche Statement that same afternoon. With more time and drier weather the snowpack continued to stabilize and the RADS level was lowered to Level 1, Unrestricted on the evening of the 15th. Most notable for the second half of the month was the arrival of weekly Arctic fronts from the northeast which dropped temperatures to below seasonal values and a brought consistent NE winds. Wind-loading onto westerly aspects became the norm. On the last day of the month another Arctic front was approaching and the snowpack, especially in locations where it was less than 3 feet deep had started to degrade and facet due to the consistently cold conditions. |
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| 2019-01-01 | 2019-01-31 | Clark | Over the month of January BNSF Avalanche Safety issued a total of six ACRs on the following dates: 01/03, 01/07, 01/10, 01/17, 01/21, and 01/28. The RADS level never rose above Level 1, Unrestricted. The mean matrix rating for the month was 33 with a minimum value of 22 on 01/10 and a maximum value of 42 on 01/07. The first 10 days of January were characterized by mostly active weather and a series of small storms. Two more avalanches ran in, or very near the Program Area that likely failed on the December facets. One was in a path known as the Shed 10 Feeder and the second was at the very top of Grizzly Gulch (the drainage between Running Rabbit and Snowslip Mountains) and in a location that does not threaten the railway. This second avalanche was un-intentionally triggered by a party of skiers. Both of these avalanches were relatively small, and in the case of the Shed 10 Feeder path, the associated debris stopped well above the rail grade. Several more large magnitude avalanches ran on the December facets in the nearby Flathead Range in early January. These slides occurred in terrain that does not threaten the railway. But the activity was a reminder that the weak basal layers in the snowpack were still capable of producing large avalanches. Beginning January 10th a strong ridge of high pressure built over northwest Montana and lasted until the 17th. This was a weeklong period of mostly dry weather and inverted air temperatures, meaning it was much colder down in the valleys than at the mountaintops. It was a period of low avalanche danger but it also created new weak layers in the snowpack. Due to the abundant sunshine and above-freezing temperatures a crust formed on the snowpack surface. There was also a layer of surface hoar, which is the winter equivalent of dew where feathery frost crystals form on top of the snowpack during clear cold nights. Once buried, surface hoar can act as a weak layer for a slab avalanche. The rest of January was quiet with very little avalanche activity and only a few small storms that gradually loaded the weak layers formed during the January 10-16th dry spell. |
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| 2018-11-01 | 2018-12-31 | Clark | Over the month of December BNSF Avalanche Safety issued a total of seven ACRs on the following dates: 12/10, 12/13, 12/18, 12/21, 12/27, 12/29, and 12/31. The RADS level never rose above Level 1. The mean matrix rating for the month was 28 with a minimum value of 7 on 12/13 and a maximum value of 42 on 12/18. The 2018-19 snowpack began developing in the Program Area by early November. During a trip to the Shed 11 weather station on Nov 8th there was 3-8 inches of snow below 6000 feet and 10-15 inches above that elevation. But the weather remained mostly dry with little accumulating snowfall for much of November and early December. In fact by the 1st week of December the snowpack at the Canyon floor had decreased in depth with little to no snow on the ground. During these weeks of dry weather the shallow snowpack that existed at upper elevations was undergoing a process known as faceting where the existing snow grains became progressively more granular (sugar-like) and lacking in cohesion due to the cold and dry weather. This weak layer of snow, was referred to as the “December facets” and was buried by the first potent storm of the winter on December 12th. Avalanche activity was minimal above the rail but field observations showed that this layer was reactive and one intentionally triggered avalanche released the following day in a location known as Test Slope 3 (photo below). Associated debris stopped well above the rail grade. No other avalanche activity was observed in the Program Area immediately following the December 12th storm. December continued with mostly active weather and two more notable storms on the 18th and the 29/30th. When the weather finally cleared on the 31st, we observed one avalanche that had run in Path 1163. It appeared that this avalanche failed on the December facets. The debris terminated 2/3rds distance down the path. Unfortunately, the weather events in November and December created a poor snowpack structure and a “persistent slab problem” which simply refers to a cohesive slab of snow layered on top of a weaker layer of snow that is much less cohesive and is resistant to strengthening. Numerous large-magnitude, life threatening avalanches were observed failing on the December facets in the nearby Flathead Range in December. Avalanche activity on this layer in the Program Area was much more limited. This was largely due to substantially lesser amounts of snow in the terrain threatening the railway. The month of December finished with below average snow depths, especially at low-mid elevations (below 5500 feet). The RADS level never rose above Level 1, Unrestricted during the entire month (table above). The shallow snow depths helped keep the railway avalanche danger low despite the poor snowpack structure and a few hefty winter storms. There just was not enough snow to create large avalanches in much of the terrain above the rail. Also there were still many obstacles (trees, brush, rocks) still not buried in the lower half of the avalanche paths, which along with the still uneven ground acted to limit the extent of avalanche debris. |
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| 2018-04-01 | 2018-04-15 | Clark | A total of 6 ACRs were issued during the month of April on the following dates: 4/1, 4/8, 4/9, 4/11, 4/13, and 4/15. Winter-like weather continued through the first half of April with below normal temperatures and continued accumulating snowfall. But in all but one case, a brief storm on the 11th, the new snow quickly bonded to the old and the RADS level remained at Level 1 until the avalanche forecasting program concluded on April 15th. Some notable avalanche activity this month occurred on the 11th when path 1163 ran approximately ¾ distance to the rail grade. Also avalanches ran in two paths known as “Curly” and “Larry” which are located on the south side of U.S. Highway 2. The associated debris travelled to within 150 feet of the highway’s right of way. No avalanche activity affected railway operations for the remainder of the spring season. After mid-April the weather turned consistently warm and dry and the deep 2017-18 winter snowpack began to rapidly melt. | |
| 2018-03-01 | 2018-03-31 | Clark | A total of 14 ACRs were posted during the month of March on the following dates: 3/2, 3/7, 3/8, 3/9, 3/10, 3/11, 3/12, 3/13, 3/14, 3/15, 3/19, 3/26, 3/29, and 3/31. Between the 7th and the 14th a melt/freeze cycle affected the Program Area which elevated the RADS rating to Level 2 of 5, Avalanche Statement on a daily basis, mostly during the warmer afternoon hours. Outside of this timeframe, the forecasted Railway avalanche danger was not elevated above Level 1 of 5, Unrestricted for 17 days. Avalanche activity in March was limited to cornice fall and loose snow avalanches. These avalanches were prompted by air temperatures climbing well above freezing along with substantial solar input. These avalanches posed little danger to Railway elements at risk and overall the snowpack structure improved substantially due to snowpack settlement and melting. From a forecaster’s perspective, the March weather combined with the improved snowpack structure greatly reduced uncertainty and was a welcome change in conditions following February’s storms. |
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| 2018-02-06 | 2018-02-06 | Steiner | Good evening; I wanted to update you on recent avalanche activity that is just now being observed as we had some clearing today. Near the Program Area and Essex large magnitude, deep slab avalanche activity occurred on a prominent peak, Mount Cameahwait, just to the south of Essex. This peak exhibited avalanche activity on both its east aspect (7 miles from the JFS Canyon portion of the Program Area) and its north aspect. All observed activity initiated between 7200 to 7500 feet elevation. It is likely both of these avalanches occurred on Sunday night as air temperatures warmed to near freezing at upper elevations, precipitation rates were moderate to heavy, and west winds were moderate with strong gusts. Cameahwait North Aspect Avalanche: In the North Aspect photo, the trigger appears to be cornice fall as much of the cornice is missing. Also in the North Aspect photo, you can see the faint line of a smaller soft slab that likely released and then stepped down into the deep slab instability. This step-down is a very-telling in regards to sensitivity of the region's deep slab instability. It didn't take much surface disturbance to cause massive failure at the basal facets which are resting on the Thanksgiving rain crust. This is the same problematic and persistent deep-seated layer responsible for the deep slab avalanches near Path 1183. Cameahwait East Aspect Avalanche: Cameahwait's east aspect avalanche is approximately seven (7) miles to the west of the Program Area and occurred at a slightly higher elevation but similar aspect of the Program Area terrain. The East Aspect avalanche was also likely triggered by cornice fall. Unfortunately the upper portion of the fracture line (crown line) is out of view. It is likely in this area that this avalanche was triggered. The length of the crown line of the East Aspect avalanche is approximately 2000 lineal feet. Based on terrain features visible on this avalanche bed surface, its depth is nearly full depth, its bed surface comprised of the Thanksgiving rain crust, and its weak layer that failed massively the December facets. Although I can not say for sure, I would not be surprised this deep slab avalanche was also triggered by an initial smaller soft slab avalanche that stepped-down into the deeper seated persistent weak layers. Regardless, for a cornice fall and/or surface soft slab to release a deep slab avalanche of this magnitude is an excellent indicator of the substantial amount of stored energy in the existing snowpack structure (at least on the night of 2/4/2018 Program Area Attributes vs. Mount Cameahwait Attributes: Terrain: Although aspect and elevation are similar between the Program Area terrain and, in particular, the East Aspect avalanche there are some major differences. First is slope angle. The Mount Cameahwait avalanche(s) occurred on far steeper terrain than what the Program Area starting zones are comprised of. Secondly, and in particular to the East Aspect avalanche, the long distance planer terrain feature associated with this avalanche does not exist in the Program Area. Snowpack: Our confidence is high that the snowpack structure associated with both observed Cameahwait avalanches was the same as what we have observed and recorded in the Program Area. Cornice development on the easterly aspects of Mount Cameahwait are very similar to what we have observed and recorded in the Program Area. Weather: I'm not sure of differences in weather that may have been present on 2/4/2018. Mount Cameahwait is certainly more prone to a intermountain (transitional) snow climate whereas the JFS Program Area snow climate is typically more continental. I guess that's it for now. If you have any question regarding recently observed deep slab avalanche activity, please feel free to email or call the mobile phone (406)-291-9671 Thank you, Ted Steiner. |
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| 2018-02-01 | 2018-02-28 | Clark | BNSF Avalanche Safety issued a total of 24 ACRs during the month of February on the following dates: 2/1, 2/2, 2/3 (x3), 2/4 (x2), 2/5, 2/7 (x2), 2/8 (x3), 2/9, 2/10, 2/13, 2/16 (x2), 2/17, 2/18, 2/19, 2/22, 2/26, and 2/27. The majority of these ACRs were issued during on or before the 10th, a period of continued winter storms and associated avalanche activity. In detail, during the timeframe between February 3rd to the morning of February 10th, the forecasted Railway avalanche danger was at Level 2 of 5, Avalanche Statement with the forecasted danger elevated to Level 3 of 5, Avalanche Watch, on the afternoon of the 4th through the morning of the 5th. A Level 3 of 5, Avalanche Watch rating was again posted for the entire day of the 8th. Driving these elevated danger ratings were a series of meso-scale weather system overrunning events in which warmer moist air was being pumped into the Program Area from the Pacific Ocean while cold, continental air (arctic air) was being drawn into the Program Area from the northeast. The collision of these warm vs. cold air masses was instigated by an air pressure gradient deficit that had set up in the Program Area region. The result of these air masses colliding and interacting was some impressively active weather with substantial snowfall, rain, wind, and dramatic air temperature swings ranging from above freezing to well below zero (°F). The greatest concern promoting the Level 3, Avalanche Watch danger ratings on the 4th and again on the 8th was the possibility that this period’s storm-related snowfall, rain, and windloading would overburden the existing poor-structure snowpack and trigger large magnitude, deep slab avalanches. At this time the potential for these large magnitude avalanches to threaten Railway elements at risk was elevated. In retrospect, natural avalanche activity that did occur during this period was moderate, although still life threatening in magnitude. But the debris associated with these avalanches terminated above the rail grade. Paths with the furthest running debris were 1163 and Infinity where it travelled to within three-quarters (3/4) distance to the rail grade. Avalanche crown lines, or the fracture lines, that were associated with the observed avalanche activity were, for the most part, obliterated by storm-related snowfall and windloading. However, some old crowns were visible and indicated that storm-related natural avalanche activity had released on both easterly aspects, loaded from prevailing west winds, but also on westerly aspects loaded from non-typical easterly winds at all elevations. Based on observations from this year and from previous seasons, it appears that loading events on the non-typical westerly aspects lead to increased avalanche activity. This is likely the result of wind-loaded snow being deposited onto a typically a shallower and weaker snowpack that is common on these west-facing slopes. Another storm cycle near the third week of February again ticked up the RADS rating to Level 2 of 5, Avalanche Statement. Fortunately during this storm cycle the air temperatures remained below freezing and the existing snowpack structure had improved in strength so a higher RADS rating was not necessary. Between the elevated avalanche forecast periods of February were relatively long bouts of forecasted Level 1, Unrestricted conditions. These conditions were supported by rather benign weather and air temperatures that were at or below seasonal norms. In total, 17 days were at Level 1 of 5 with no recommended restrictions being advised for Railway operations. |
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| 2018-01-01 | 2018-01-31 | Clark | BNSF Avalanche Safety issued a total of 19 ACRs on the following dates: 1/1, 1/3, 1/4, 1/6, 1/8, 1/9 (x2), 1/10, 1/11, 1/12, 1/15, 1/18, 1/22, 1/25, 1/27, 1/28, 1/29, and 1/30 (x2). The mean matrix rating from the 19 ACRs was 45 with a minimum value of 25 on 1/15 and a maximum value of 70 on 1/30. The New Year began with drier weather and the RADs rating was lowered to Level 1. For the next week high pressure conditions dominated the region with mostly dry and benign weather. Beginning the afternoon of January 9th however temperatures began to warm as a system from the Pacific moved in and brought rain and wet heavy snow. Over the next three days temperatures cooled but the weather remained wet and another 20 inches of snow was added to the snowpack. By the 12th a lack of avalanche activity indicated that this new snow was bonding well and stabilizing and the RADS rating was reduced back to Level 1 that afternoon. For the next two weeks the Program Area was under the influence of either brief periods of high pressure or westerly or zonal flow that brought only small amounts of new snow with each passing storm. The only notable avalanche activity was a cornice fall avalanche in Shed 7 West on January 27th where the debris ran 2/3rds path. Warming temperatures, rainfall below 5000 feet elevation and heavy wet snowfall above this elevation necessitated a bump up in the RADs rating beginning the 28th and lasting until the afternoon of the 30th when temperatures cooled back to normal and the recent storm snow quickly stabilized. |
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| 2017-12-21 | 2017-12-21 | Steiner | 12/21/2017 @2015 Good Evening; Given the recent storm cycle and associated natural avalanche activity I thought I would write a review, overview, and outlook of our current snowpack and potential avalanche situation. Early Season in Review: Early November brought the Program Area accumulating snow with new snow depths of eight inches to twenty inches (8"-20") depending on aspect and elevation. This snowfall was accompanied by variable wind speeds and arctic air influence. Air temperature toward the end of this storm system's influence dropped into the single digits (F). Mid-November conditions were relatively dry and seasonably cool. Third week of November brought increased air temperatures at all elevations and substantial rain. This rain either melted off snow or created a substantial crust on the snowpack surface at the time. Late November through the first two weeks of December weather conditions were relatively dry with a strong, persistent high pressure ridge that lasted through mid-December. Through December 15th only four to six inches (4" to 6") of snow depth was present at Program Area Canyon floor elevations. A substantial amount of Program Area terrain was completely void of any snowpack at all. However, in particular, the lower angle starting zones with shaded aspects at upper elevations had retained over 12" of snow depth from earlier season snow events. Beginning on the afternoon of the 15th high pressure conditions were replaced by an unstable atmosphere and with the transition, two to three inches (2"-3") of new snow accumulation was deposited at all elevations in the Program Area. On Sunday, December 17th, air temperatures warmed and precipitation continued which established a substantial rain crust at elevations below 5000 feet in the Program Area and region. It was also on the afternoon of the 17th that the National Weather Service posted a Winter Storm Warning and predicted up to 50" of new snowfall for the Program Area between December 18th and 20th. December 18th through 20th; Snow. Accumulation rates between one and two inches (1"-2") per hour. Storm conditions for the duration produced relatively low density snow and light to moderate variable winds at all elevations. Settled storm total snow accumulation averaging 32" is deposited at canyon floor elevations in the Program Area. Post-storm total snow depths range between 24" and 30". Snowpack and Avalanche Conditions Overview Based on 12/20/17 Field Observations: Skies clearing, air temperatures remained well below freezing at all elevations, and winds were calm. Based on conditions a conservative decision was made to travel into the field utilizing terrain adjacent to the Burnout avalanche path in the Program Area. Areas adjacent to the starting zone of the Burnout avalanche terrain was our destination of field observations. On our vehicle drive to begin our ski tour, visibility improved enough to see widespread direct action avalanche activity associated with the December 18th-20th storm in and around the Program Area. Very small to small magnitude avalanche activity on steep lower elevation terrain (D1-D1.5). Larger magnitude activity in mid and upper elevation Program Area avalanche prone terrain (D2-D3). All observed avalanche debris associated with activity terminated above rail grade and/or Canyon floor elevations. Difficult ski-travel conditions utilizing heavy timbered slopes and/or slope angles of less than 30 degrees allowed us to only gain the starting zone elevation of the Burnout avalanche path (5300 feet a.s.l). During our ascent to the Burnout starting zone, snowpack instability was substantial with nearly constant audible collapsing and shooting cracks in the snowpack (massive snowpack failure) under the weight of one skier. Enough energy was being released from instigating these collapses that snow was being rattled from trees and cracks in the snowpack were remotely propagating across inclined terrain of greater than ~35 degrees. Snow profile and stability tests conducted and recorded in a 110 cm snowpack at the upper most point of our tour (5300 feet a.s.l.) revealed 90 centimeters (3 feet) of relatively low hardness (density) storm snow deposited on 20 centimeters (8 inches) of sugar snow (facets) with very little cohesive properties (*Note Graph to the Lower Right). Conclusive ECT stability test resulted in propagation with one test recording of ECTP 26@90. The other ECT test required two more blows from the shoulder than the standard 30 but completely propagated across the column at 32. Snowpack Conditions & Avalanche Outlook: While touring yesterday we encountered the greatest widespread instability in the Program Area snowpack that I have experienced while conducting field observations over the past 12 seasons. We also observed numerous avalanches that had occurred on various aspects, elevations, and locations. There is NO REASON to believe this instability is limited to the Burnout Area. I believe we have a snowpack instability problem that is inclusive of the entire Program Area; at all elevations and on all aspects. Snowpack condition that currently exists in the Program Area is referred to as a persistent slab problem which simply refers to a mass of snow layered on a persistent, unstable underlying layer of snow that has poor cohesive qualities (facets). In even more accurate terms what we are dealing with is a persistent deep slab problem as the significant instability in this season's Program Area snowpack exists at the basal layer interface. The Program Area's persistent deep slab problem, which is susceptible to triggering for long periods of time (months) has the ability to propagate over long distances and produce large magnitude, life threatening, and infrastructure damaging avalanches. The key point being that the poor snowpack structure related to December 18th's storm has elevated the potential of large magnitude natural avalanche activity, not just in the near-term but for an extended period on the order of months. This is what we're up against and conservative, avalanche-cognizant decision-making will be critical to helping ensure an avalanche-incident-free season for both train and maintenance operations. Please call or email if you would like to discuss more about existing and future snowpack/avalanche conditions. Thank you, Richard (Ted) Steiner BNSF Avalanche Safety Consultant. (406)291-9671 |
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| 2017-12-01 | 2017-12-31 | Clark | BNSF Avalanche Safety issued a total of 15 ACRs on the following dates: 12/18, 12/19(x2), 12/20, 12/21, 12/22, 12/23, 12/26, 12/27, 12/28, 12/29, 12/30(x2), and 12/31.The mean matrix rating from the 15 ACRs was 56 with a minimum value of 34 on 12/26 and a maximum value of 80 on 12/30. For the first half of December a stubborn high pressure ridge parked itself over the western United States. The result was a 2 week+ period of mostly dry weather which caused the shallow snow on the ground to become quite weak due to a process called faceting. Here the existing snow grains become increasing angular and lacking in cohesion and eventually resemble the consistency of sugar. This was a widespread problem across the western US and this layer of faceted snow became known as the December Dry Layer (DDL) amongst avalanche professionals nationwide. The BNSF Avalanche Program was no exception and the early December weather created a snowpack structure that was weak at the base and the DDL remained a layer of concern for much of 2017-18 season. Beginning late 12/18 a winter storm struck the region and over the course of the next 3 days over 4 feet of new snow accumulated in the Program Area. There was widespread natural avalanche activity and the RADS level rose to Level 2 and remained there for almost 5 days. Several avalanches ran in terrain threatening the railway including paths: 1163, Shed 10, Shed 9, and Shed 7 East. All associated debris travelled to within 1/3rd distance from the rail grade in their respective paths. By 12/24 the snowpack stabilized enough to bring the RADs level back down to Level 1. After a brief lull during and just after Christmas an even more potent winter storm impacted the Program Area beginning 12/28 and deposited another 2-4 feet of snow over the next 48 hours. Initially the RADs level was elevated to Level 2 on 12/28. Increase in the RADS was due to the quickly increasing new load being placed on top of the weak basal layer. Then on 12/29 several small magnitude avalanches released naturally on steep cut banks above the rail along with Jakes and Path 1164. Avalanche debris from all these natural avalanches was deposited on the rail grade. The RADS level was elevated to Level 3 of 5, Avalanche Watch during the late morning hours on 12/30 following a large magnitude (Destructive size 3) avalanche was observed in the Infinity path. Debris associated with this avalanche terminated just short of the rail grade with air blast debris being deposited on the grade. Following the Infinity avalanche, BNSF Avalanche Safety went to investigate the avalanche site. Examination of the site revealed that mature trees were destroyed by the avalanche less than 50 yards upslope from the rail grade and that a very powerful air blast had broken tree limbs along the rail grade and on the opposite side of the rail grade from the avalanche path. The RADS level remained at Level 3 for the rest of 12/30. After avalanche activity decreased and weather conditions improved, the RADS level was lowered to Level 2 on 12/31. |
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| 2017-04-13 | 2017-04-13 | Steiner | Currently, the Railway Avalanche Danger rating remains on the very low end of Level 2 of 5, Avalanche Statement with an associated Matrix score of 50. What this means is that the overall likelihood of life threatening avalanche activity occurring in Program Area avalanche prone terrain remains possible. However, my confidence (which is reflected in the Matrix Score, in avalanche activity that does occur reaching rail grade elevations in the Program Area is low. The associated Matrix Score is comprised of, it is a cumulative number, in this case 50, of 13 different avalanche-related variables that are “scored” between zero and ten (0 and 10). Scoring of each variable is subjective and estimated by the forecaster (me). However, whatever the score for a particular variable is, represents “forecaster concern” regarding each of the 13 variables… 0 representing NO CONCERN and 10 representing SIGNIFICANT CONCERN. The level of CONCERN for each variable being driven by either objective data or degree of uncertainty. In the Matrix numeric parameters for Level 2 of 5, Avalanche Statement, ranges between 50 and 75. So, why L2 of 5 and 50 for nearly two (2) days? • Recent avalanche activity. • Instability observed in the near surface snow structure. • Recent weather conditions. Recent avalanche activity (observed Wednesday) indicated that instability in the near-surface snowpack exists and also provided strong evidence that associated debris with whatever avalanche activity occurred had associated magnitude to carry small to moderate amounts of debris at or near rail grade elevations. However, NO avalanche activity was observed and/or reported through yesterday or last night. Snowpack stability tests conducted during last Tuesday’s field observations indicated a reactive weak layer observed at different elevations and on different aspects approximately two feet (2’) from the snowpack surface. Yesterdays and last night’s storm deposited between six and ten inches (6”-10”) of new snow at mid and upper starting zone elevations in the Program Area. On the Canyon floor, much of what fell yesterday melted and total amounts being recorded this morning are around four inches (4”). Winds throughout the storm were relatively light with stronger southwest gusts and air temperatures decreased to below freezing at all Program Area elevations due to the passing of a cold front… This morning, air temperatures are in the low 30 0F at Canyon floor elevations and in mid-20s 0F at upper starting zone elevations. My decision to remain at L2 through this morning was due to the possibility that storm predicted snowfall with increased water content may be substantial enough to provide overburdening stress to the surface snowpack and potentially trigger avalanche activity similar to what was observed Wednesday. With weather conditions improving and no reported and/or observed avalanche activity in the past 24 hours, my plan is to reduce the Railway Avalanche Danger rating back to Unrestricted after this morning’s Canyon based observations. New RAD rating should be posted by 1030. Thank you, Richard (Ted) Steiner |
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| 2017-03-01 | 2017-03-31 | Clark | March 2017 Summary Conditions Report: BNSF Avalanche Safety issued a total of 9 ACRs on the following dates: 3/2, 3/7, 3/10, 3/17, 3/21, 3/24, 3/28, 3/31. The RADS level never rose above Level 1. The mean matrix rating was 21 with a minimum value at 13 on 3/31 and a maximum value at 34 on 3/10. Spring came early this year to the Program Area. For most of March temperatures were above average with multiple rain events. Thus the snowpack at low to mid elevations consistently melted away. By the end of the month much of the avalanche terrain below 5500 feet was snow free even though most of the month experienced fairly wet weather. Above 6000 feet the snowpack continued to maintain and even increase slightly in depth and remained near average for late-winter/early spring. The first half of the month brought unsettled weather with a continuous series of small storms. On 3/17 the strongest storm of the month dropped 10-12 inches of snow at upper starting zone elevations. High pressure developed over the next three days with sunny skies and warm temperatures. Small wet loose avalanches ran in several paths above the rail grade. All debris terminated in the upper 1/3 of the paths. The avalanche hazard to the rail was minimal by the end of the month. This was due to the lack of snow at the low-mid elevations and a mostly stable snowpack in the upper-elevation starting zones. |
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| 2017-02-01 | 2017-02-28 | Clark | February 2017 Summary Conditions Report: BNSF Avalanche Safety issued a total of 26 ACRs during the month of February on the following dates: 2/3 (x2), 2/4 (x2), 2/5 (x3), 2/6, 2/7 (x2), 2/8, 2/9 (x3), 2/10 (x2), 2/11, 2/12, 2/15, 2/16, 2/17 (x2), 2/20, 2/25, 2/27 and 2/28. Fifteen ACRs were issued during the Feb. 4-10th period when a large-scale avalanche cycle suspended railway operations at two different times. Two ACRs were issued on Feb. 3 while the hazard was increasing but the danger rating remained at Level 1. On Feb. 4 the RADS rose to Level 2 and remained there until the PM hours of Feb. 5th when it rose to Level 3. The next day it increased again to Level 4 and remained there until the PM hours of Feb. 7th. However due to the extreme winter weather, railway operations had effectively halted. A mitigation mission was held on the 7th which resulted in several small to medium-sized avalanches (D1-D2) a few of which reached the rail grade. After the mission the RADS was lowered to Level 3 and operations resumed under the accompanying restrictions. That is until the morning of Feb. 9th when a large-magnitude avalanche ran in path 1163. The associated debris buried both mains, tore out the slide fence, and dusted the pavement on US Highway 2. Fortunately cooling temperatures stabilized the snowpack quickly on Feb. 10th and around noon the RADS was lowered to Level 3 and train operations once again resumed. The following day the rating was dropped to Level 2 where it remained for most of the following week. Between Feb. 16th and the end of the month the RADS was kept at Level 1 except for one brief 20-hour period on the 20th when a period of warm weather accompanied by rain caused an increase to Level 2. The mean matrix rating for the month was 66 with a minimum value of 29 on 2/25 and a maximum value of 111 on 2/9. BNSF Avalanche Safety toured for a total of four days above the rail during February to assess snowpack and avalanche conditions in the upper elevation terrain. A complex series of weather events ensued during the first eleven days of February which led to a widespread avalanche cycle that included numerous large-magnitude destructive slides. From Feb. 3-6th the weather was very unsettled as cold arctic air from the northeast interacted with warm and moist air flowing in from the southwest. These two air masses were constantly vying for control over the Program Area and the result was exceptional amounts of snowfall. Over the course of these four days over 50 inches of snow fell at the Canyon Floor elevations. Moderate to strong winds would swap back and forth from easterly to westerly directions and temperatures would fluctuate several tens of degrees in only a matter of hours. But on Feb. 8th the warm air from the Pacific won out and temperatures began to climb rapidly. Early on the 9th it began to rain and by the end of the day almost 1.5 inches had fallen across the area. Several large magnitude avalanches ran on the 9th in John F Stevens Canyon and across northwest Montana. Beginning Feb. 10th the rain ceased, temperatures began to drop to more seasonable levels, and the snowpack quickly stabilized. A period of high pressure ensued from Feb. 12-15th with clear and sunny skies and afternoon temperatures once again rising above average. A loose wet avalanche cycle accompanied this warm up but no debris reached to rail grade. The remainder of February experienced more seasonable weather with typical sub-freezing temperatures and moderate gains in snow depth with each passing storm. The first week of February had seasonable weather with a series of small storms with steady westerly winds that loaded SE-E-NE aspects. Beginning 2/9 a very strong ridge of high pressure developed over the Program Area. Temperatures at Canyon floor elevations reached into the 50s °F and remained above freezing at elevations up to 7000 feet for three straight days. Small wet loose avalanches ran in several paths but debris terminated in the upper 1/3, well above the rail grade. High pressure broke down around 2/13 but overall the weather remained mostly unseasonably mild for February. The snowpack below 6000 feet began to melt and by the last week of the month it wasn’t possible to ski all the way to the Canyon floor. Above 6000 feet snowpack depths continued to increase but remained mostly stable with no notable avalanche activity for the rest of the month. Ted taught one BNSF avalanche safety class to a night shift crew on 2/3. |
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| 2017-01-01 | 2017-01-31 | Clark | January 2017 Summary Conditions Report. BNSF Avalanche Safety issued a total of 16 ACRs on the following dates: 1/3, 1/6, 1/8, 1/9 (x2), 1/10, 1/14, 1/16, 1/17, 1/18 (x2), 1/19 (x2), 1/23, 1/28, and 1/30. The RADS level remained at Level 1 except for the PM hours of 1/18 and AM hours of 1/19 when it increased to Level 2. The mean matrix rating for the month was 39 with a minimum value of 20 on 1/23 and a maximum value of 50 on 1/18 and 1/19. BNSF Avalanche Safety put in a total of five field days above the rail grade in order to observe snowpack and weather conditions in our upper elevation terrain. January began under the grips of a frigid Arctic air mass. Temperatures plummeted at night sometimes reaching as cold as -30° F. Daytime temperatures struggled to rise above 0°F. These bitterly cold temperatures were sometimes accompanied by light to moderate easterly winds which continued to load westerly aspects in the Program Area. An over-running event occurred Jan. 8-9 with warmer air aloft and increasing west winds. But another Arctic front pushed in on Jan. 10 returning the area to the deep freeze. Beginning Jan. 17 a warm system from the southwest push into the region. Freezing levels rose above 7000 feet elevation and precipitation came as a rain/snow mix. The warm weather continued through Jan. 19th and caused widespread loose snow avalanche cycle that occurred primarily at low elevations. Debris from several small loose snow avalanches reached the rail from steep cut banks located above the grade. A larger (D2) avalanche ran in path 1163 with debris terminating at 2/3rd path. Soon after temperatures dropped to below freezing creating widespread crust which we referred to as the Jan 19th crust for the remaining season. The rest of the month was characterized by quiet weather with seasonable temperatures and occasional weak systems that brought only small amounts of accumulating snow. |
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| 2016-12-01 | 2016-12-31 | Clark | December 2016 Summary Conditions Report: BNSF Avalanche Safety issued a total of 9 ACRs on the following dates: 12/11, 12/16, 12/19, 12/20, 12/23, 12/26, 12/28, and two on 12/30. The RADS level never rose above Level 1 except for the AM hours on 12/30 when it briefly increased to Level 2. The mean matrix rating for the month was 37 with a minimum value of 30 on 12/23 and a maximum value of 50 on 12/30. BNSF Avalanche Safety put in five field days in December where we toured above the rail grade to asses snowpack conditions in the upper elevation starting zones of our avalanche terrain. During these field days we also repaired and/or improved our weather stations at Shed 11 and Shed 7 East. December was a cold and windy month with about average precipitation. Several arctic air masses moved over the region bringing an abundance of easterly winds and below normal temperatures. The snowpack accumulated at a steady rate with a consistent series of storms that never deposited more than about 12 inches of snow at a time at all elevations. Due to the cold temperatures the storm snow was of exceptionally low density and easily available for wind transport. The result was heavy wind-loading onto both easterly and westerly aspects in our avalanche terrain. Wind slabs and cornices grew at a steady rate and by late December we had observed cornice-fall and wind slab avalanches. Most of these slides terminated in the upper 1/3rd of our avalanche paths. But on 12/30 avalanches ran about 2/3rds distance down paths 1163 and Shed 7 West. In locations more sheltered from the wind the snowpack was faceting for most of the month. By the end of December the snowpack was composed mostly of facets at low to mid elevations and at the upper elevations in non-wind affected terrain. |
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| 2016-03-01 | 2016-03-31 | Clark | BNSF Avalanche Safety issued a total of 9 ACRs on the following dates: 3/2, 3/7, 3/10, 3/17, 3/21, 3/24, 3/28, 3/31. The RADS level never rose above Level 1. The mean matrix rating was 21 with a minimum value at 13 on 3/31 and a maximum value at 34 on 3/10. Spring came early this year to the Program Area. For most of March temperatures were above average with multiple rain events. Thus the snowpack at low to mid elevations consistently melted away. By the end of the month much of the avalanche terrain below 5500 feet was snow free even though most of the month experienced fairly wet weather. Above 6000 feet the snowpack continued to maintain and even increase slightly in depth and remained near average for late-winter/early spring. The first half of the month brought unsettled weather with a continuous series of small storms. On 3/17 the strongest storm of the month dropped 10-12 inches of snow at upper starting zone elevations. High pressure developed over the next three days with sunny skies and warm temperatures. Small wet loose avalanches ran in several paths above the rail grade. All debris terminated in the upper 1/3 of the paths. The avalanche hazard to the rail was minimal by the end of the month. This was due to the lack of snow at the low-mid elevations and a mostly stable snowpack in the upper-elevation starting zones. |
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| 2016-02-01 | 2016-02-29 | Clark | BNSF Avalanche Safety issued a total of 9 ACRs on the following dates: 2/2, 2/6, 2/9, 2/11, 2/14, 2/17, 2/20, 2/22, and 2/29. The RADS level never rose above Level 1 but the matrix rating did peak at 49 (highest value for Level 1) on 2/20 and it reached 48 on 2/6. The mean matrix rating was 37 with a minimum value at 20 on 2/29. The first week of February had seasonable weather with a series of small storms with steady westerly winds that loaded SE-E-NE aspects. Beginning 2/9 a very strong ridge of high pressure developed over the Program Area. Temperatures at Canyon floor elevations reached into the 50s °F and remained above freezing at elevations up to 7000 feet for three straight days. Small wet loose avalanches ran in several paths but debris terminated in the upper 1/3, well above the rail grade. High pressure broke down around 2/13 but overall the weather remained mostly unseasonably mild for February. The snowpack below 6000 feet began to melt and by the last week of the month it wasn’t possible to ski all the way to the Canyon floor. Above 6000 feet snowpack depths continued to increase but remained mostly stable with no notable avalanche activity for the rest of the month. Ted taught one BNSF avalanche safety class for a night shift crew on 2/3. |
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| 2016-01-01 | 2016-01-31 | Clark | BNSF Avalanche Safety issued a total of 10 ACRs on the following dates: 1/5, 1/13, 1/14, 1/19, 1/20, 1/22, 1/24, 1/27, and two on 1/30. The RADS level never rose above Level 1 but the matrix rating did peak at 49 (highest value for Level 1) on 1/30. The mean matrix rating was 40 with a minimum value at 16 on 1/5. A strong ridge of high pressure dominated over the Program Area for almost the first 2 weeks of January. This period was characterized by light and variable winds, very little precipitation, and strong temperature inversions where it was not uncommon for low temperatures at the Canyon Floor to fall below 0°F and struggle to reach the teens °F of by the afternoon. Meanwhile at ridgetop locations, low temperatures would barely fall below freezing and would reach the 40s °F by the afternoon. Warm air aloft brought freezing rain up to the ridgetop altitudes on 1/13 and the rest of the month was characterized by active weather with consistent storms dropping 4-12 inches of snow, often accompanied by moderate to strong W to SW winds. Freezing levels rose to 6000 feet on 1/22 but then cooler, more seasonable temperatures prevailed for the rest of the month. Notable avalanche activity included: several intentionally triggered wind slabs in Test Slopes 1 and 2, including a D1.5 in Test Slope 2 that failed on a buried surface hoar layer, loose avalanche debris that ran 2/3 path in 1163 on multiple occasions, and a large cornice fall in Shed 7 W sometime between 1/27 and 1/30. Of note this cornice fall did not trigger another avalanche on the slope below. We taught two BNSF avalanche classes, one for signal maintainers on 1/12, and another for the maintenance crews on 1/28. We also flew the Daisy Bell with Minuteman Aviation on a training mission in the Schellinger Gravel Pit on 1/6. |
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| 2015-12-01 | 2015-12-31 | Clark | BNSF Avalanche Safety issued a total of 9 ACRs on the following dates: 12/1, 12/13, 12/15, 12/19, 12/20, 12/22, 12/24, 12/25, and 12/29. The RADS level never rose above Level 1. The mean matrix rating value was 23 with a minimum value on 12/15 and a maximum value on 12/25. December began under a ridge of high pressure that had been parked over the Program Area for much of the previous week. Snow depths were far below average at all elevations. Small, weak storms brought only minor amounts of snow for the first half of the month. Of note, on Dec 9, heavy rain fell up to almost 7000 feet. We did not reach the upper elevation starting zones until 12/15 when we climbed up to the Shed 11 weather station and found only 8-20” (20-50 cm) of snow. We were only able to ski about 800 vertical feet below the station due to the abnormally thin snow cover. Beginning around 12/19 a series of strong storms moved through the Program Area including one storm that occurred between 12/22 and 12/24 where upwards of 2 feet of snow fell. The snowpack quickly gained depth and by the time another high pressure system began building around 12/26, snow depths were near average, to even slightly above. Winds were predominately light to moderate from the W and SW and temperatures generally remained below freezing at all elevations. Only minor windslab avalanches were observed in Paths Shed 7, Shed 8, and Infinity. In all cases debris terminated in the upper 1/3 of the path. We taught one BNSF avalanche class for signal maintainers on 12/22. We also flew the Daisy Bell with Two Bear Air on a training mission in the Schellinger Gravel Pit on 12/10. |
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| 2015-04-01 | 2015-04-15 | Steiner | April is again a warm and dry month. The snowpack has totally melted out at all Canyon floor locations in the Program Area. Seasonal snowpack elevations have climbed to approximately 1670 meters (5500 ft.). No significant snowfall or avalanche activity in the Program Area during this period. Weather conditions continued to be warm and dry. | |
| 2015-03-01 | 2015-03-31 | Steiner | Warm and dry conditions persist. Elevation of the snowline in all Program Area avalanche prone areas has climbed to above 1500 m (5000 ft.). As a result, no avalanche hazard in the Program Area existed for Canyon floor elevations by the middle of March. Again, during this period, no significant snowfall nor avalanche activity. It is a warm and dry winter. | |
| 2015-02-01 | 2015-02-28 | Steiner | Warm air temperatures and dry conditions have continued through this month. As a result of warmer conditions than normal, precipitation that has occurred has accumulated as snow at elevations above 1670 meters (5,500 ft.) and a rain/snow mix or rain at elevations below 1670 m. Snowpack depth continues to wane at lower elevations and, in some locations, has begun to melt out at lower elevations in Program Area avalanche paths- exposing bare ground. No significant snowfall events nor avalanche activity has occurred during this period. This is the warmest and driest February recorded in the Program Area since the beginning of the avalanche program. |
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| 2015-01-11 | 2015-01-31 | Steiner | During this period air temperatures warmed above average and precipitation that did fall fell as snow at higher elevations and a rain/snow mix at lower elevations. No significant slab avalanche activity was observed or recorded. Best skiing of the year, based on coverage occurred in the last week of January. Overall, air temperatures are above the norm, snowfall is below the norm, and overall snowpack coverage is lower than observed any previous Program year. | |
| 2015-01-01 | 2015-01-10 | Steiner | Light to moderate snowfall rates and accumulation. Air temperatures were seasonal to below seasonal and were affected by the onset and regression of arctic influenced weather events. Winds were light to moderate and alternated between west and east depending on influencing weather event. The most significant snowfall accumulation occurred on 1/6/15 and consisted of approximately 60 cm in 48 hours. This weather event began cold and warmed as the storm progressed. Given this weather situation and a persistently weak basal and mid-depth snowpack a moderate sized avalanche cycle ensued at all elevations. Weak layer/ bed-surface interfaces were related to late November and mid-December interfaces. No associated avalanche debris reached the rail grade. However, the Gauntlet did produce widespread avalanche activity and debris reached rail grade elevation at this location. All other paths that ran terminated at least 2/3rds distance to the rail grade. |
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| 2015-01-01 | 2015-01-10 | Steiner | Light to moderate snowfall rates and accumulation. Air temperatures were seasonal to below seasonal and were affected by the onset and regression of arctic influenced weather events. Winds were light to moderate and alternated between west and east depending on influencing weather event. The most significant snowfall accumulation occurred on 1/6/15 and consisted of approximately 60 cm in 48 hours. This weather event began cold and warmed as the storm progressed. Given this weather situation and a persistently weak basal and mid-depth snowpack a moderate sized avalanche cycle ensued at all elevations. Weak layer/ bed-surface interfaces were related to late November and mid-December interfaces. No associated avalanche debris reached the rail grade. However, the Gauntlet did produce widespread avalanche activity and debris reached rail grade elevation at this location. All other paths that ran terminated at least 2/3rds distance to the rail grade. |
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| 2014-12-21 | 2014-12-31 | Steiner | Seasonal conditions in regards to air temperature. Lack of precipitation and wind in comparison to the norm. No significant avalanche activity. | |
| 2014-12-01 | 2014-12-20 | Steiner | This time period was dominated by either high pressure weather systems and associated inversions and/or split flow weather patterns. Only light snowfall was recorded during this period at all elevations with snow depths at all elevations decreasing. No avalanche activity was observed or reported. On 12/4/2014 we did conduct a weather station maintenance field visit to the Shed 11 Weather Station. Although no formal snowpack observations were conducted during this tour, surface snowpack (10 cm) was well faceted and beneath facets was a well established melt/freeze crust. It appeared basal snow consisted of poor structure from ski pole penetration. Audible failures were experienced during this field visit. As of 12/20, no formal field observations have taken place above the grade due to a shallow snowpack and hazardous travel conditions. Also, as of 12/20/14, the only avalanche activity observed in the Program Area has been in Path 1163. On 12/16/14 avalanche debris was observed about 2/3rds path. No crown was visible. |
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| 2014-11-01 | 2014-11-30 | Steiner | 11/1/2014-11/2/2014: Heavy liquid precipitation followed by arctic event and accumulating snowfall at all Program Area elevations. Air temperatures well below 0 degrees F. No avalanche activity observed or reported. T gradient having negative effects on structure of existing snowpack. 11/3/14-11/15/14: Unseasonably cold with accumulating snowfall. 11/15/14-11/27/14: Warming trend to unseasonably warm air temperatures. Snow depth decreases significantly at all elevations. 11/28/14-11/29/14: Significant moisture plume settles over area bringing high elevation rain and wet snow. 11/29/14: Afternoon into evening. STRONG arctic front impacts Program Area. Strong easterly winds, uprooted trees, power outages, and infrastructure damage. Air temperatures plummet. 11/30: Cold air has settled into the Program Area with air temperatures below zero and minimum air temperatures reaching -20 degrees F. |
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| 2013-10-15 | 2013-11-30 | Steiner | Accumulating snows began at all elevations in the Program Area beginning in mid-October. All Starting zones had melted out by the third week of October. Beginning 11/2/2013, the seasonal snowpack began accumulating at all elevations in the Program Area. Although air temperatures above freezing and rain have reduced initial snow depths at elevations below 5800 feet elevation (1760 m), the snowpack above this elevation has continued to deepen throughout November. Significant mixed precipitation event(s) occurred on 11/8 and 11/17-18 with rain below 5,800 feet elevation and snow at higher elevations. A well established High Pressure event occurred between 11/19 and 11/29. During this Hp event, air temperatures dropped below 0 degrees F at all elevations in the Program Area and remained well below freezing for the entire period. Development of surface hoar and near surface facets was observed near the Program Area and near starting zone elevations. In Essex surface hoar measured was measured up to one inch (1")(2.5cm) in length. Hp began to break down on the evening of 11/30. On 11/27, there was reported avalanche activity on the south face of Shields Mountain- adjacent to the Program Area. No slab avalanche activity was observed in the Program Area. We did not travel in the Program Area starting zones during November and collected no manual field data during this time. |
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| 2013-03-15 | 2013-04-04 | Steiner | Weather conditions during this time were dominated by a dirty ridge pattern with some high pressure dominated weather days. Overall, air temperatures were above average and precipitation that did occur resulted in rain below 5,500 feet elevation and snow accumulation at higher elevations. By 4/3/2013 air temperatures were reaching the 60s F and snow threatening Railway elements had melted off lower and mid elevation avalanche paths. Upper elevation avalanche paths with starting zones above 6,200 feet elevation retained and gained in snowpack depth but surface roughness associated with the lower third (1/3) of these paths increased substantially and eliminated the ability for avalanche activity generated by these paths from reaching the rail grade. The Shed 11 Glide Crack did fail massively between 4/2 and 4/3/2013. Debris carried to 400 vertical feet above the Shed 11 Snowshed. | |
| 2013-03-08 | 2013-03-14 | Steiner | Blocking ridge continues to dominate region... Air temperatures initially warming into the 40s with rain line climbing to 1800m on 3/11/12. Air temperatures REALLY spike on 3/14 to 10C (50F)! Minimal slab avalanche activity observed during this time. | |
| 2013-03-05 | 2013-03-07 | Steiner | Light snow accumulations being recorded with pulses of weather pushing through weak developed ridge. | |
| 2013-03-02 | 2013-03-03 | Steiner | Natural avalanche activity was observed from US Highway 2 at approximately 1445 on 3/2/2013. Activity observed occurred on the northerly aspect of Nyack Mountain in the Middle Fork corridor and associated debris ran into both Cascadilla and Rescue basins. Starting zone elevation was approximately 7,000 feet and terminus elevation was approximately 5,400 feet. Avalanches appear to have been triggered by cornice fall, were soft slab in character and associated crown depths were approximately 100 to 130 cm. Interface of slab and bed surface appeared to be old snow. Crown length of the Cascadilla avalanche was greater that 200 meters and the Rescue avalanche approximately 50 meters. Terrain associated with avalanche activity was steep, unconfined slopes with poor buttressing. Steiner. |
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| 2013-03-01 | 2013-03-03 | Steiner | Warm and wet storm cycle... NW flow associated with Jet wrapping down from Canada. Mild air temperatures and rain to 1800m. Slab avalanche cycle associated with this weather is widespread... Observed from Marias Pass to Cascadilla Creek drainage. Avalanche activity observed appears to have initiated at elevations above 1800m and all debris terminated at elevations above 1600m. Avalanche up to Destructive Size 3 was observed on the northerly aspects in Cascadilla Creek and Sheep Creek... Appears a moderate size slab release occurred in Shed 9... Debris terminated above the mid elevation nick point. | |
| 2013-02-19 | 2013-02-26 | Steiner | Another shot of snowfall associate with weak low pressure system... 31cm HST at Java Manual Weather Obs. site. | |
| 2013-02-13 | 2013-02-18 | Steiner | High pressure breaks down. Weak low pressure system moves over area. Warm... up to 41cm HST (Devil Creek Manual Weather Obs Site). No avalanche activity observed or reported. | |
| 2013-01-31 | 2013-02-12 | Steiner | Moderate west winds transporting available snow onto easterly aspects. Significant cornice development... Surface windslab formation on easterly aspects... High pressure (split flow) develops on 2/1 and continues through 2/12/2013... WARM. Only slight snowfall during this time- low density... 5cm (2")(Low Elevations)15cm (6")(Upper Elevations). No avalanche activity observed or reported. | |
| 2013-01-28 | 2013-01-29 | Steiner | Temperatures cooling... 25 cm HST at 1700m (5940ft) and above. Arctic air moves in on 1/29/13... Moderate east winds (-20C)... West aspects loading. | |
| 2013-01-24 | 2013-01-26 | Steiner | High pressure scrubbed out. 1/24... 7cm HST- low density. 1/25-26... 10cm HST with increased density... Canyon floor elevations... Temperatures increasing. RAIN to 1550m. |
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| 2013-01-16 | 2013-01-23 | Steiner | High pressure strengthens. Inversion exists. PWL form... Surface hoar, Near surface facets associated with melt/freeze crust. | |
| 2013-01-11 | 2013-01-15 | Steiner | Weak high pressure ridge developing. Air temperatures cooling... HST 25cm- low density. | |
| 2013-01-07 | 2013-01-10 | Steiner | High pressure finally breaks down. Moderate to strong west winds at ridgetop elevations, Rain to 1600m. 32cm HST at elevations above 1700m. Strong west winds at ridgetop elevations on 1/9/2013. | |
| 2013-01-02 | 2013-01-06 | Steiner | Strong high pressure develops. Surface hoar and near surface facets forming at elevations above 1500m (5000ft). Sun crust forming on direct solar aspects above 1750m (5700ft). | |
| 2012-12-26 | 2013-01-01 | Steiner | Happy New Year! Low density snow accumulation, 20cm, in Program area associated with previous arctic event and then with westerly weather influence. Moderate west winds transport available snow onto recently scoured easterly aspects above 1700m (5,600ft). | |
| 2012-12-18 | 2012-12-25 | Steiner | Snowfall and storm systems tapering off. First short burst of arctic air moves into Program area with moderate east winds and air temperatures dipping to -20C at Canyon floor elevations. Easterly aspects scoured. | |
| 2012-12-10 | 2012-12-17 | Steiner | Storm cycle continues. 52 HST in Essex between 12/13 and 12/17. Strong west winds. | |
| 2012-12-07 | 2012-12-08 | Steiner | Significant snow storm. 40 cm HST on Canyon floor. 60cm above 1500 m (5,000 ft.) Moderate to strong west winds and air T -15C | |
| 2012-12-01 | 2012-12-02 | Steiner | Accumulating snow above 4300 feet elevation. Appears to be staying put for the season. Air Ts continue to be relatively warm... -5C. | |
| 2012-11-01 | 2012-11-30 | Steiner | Warm and wet conditions~ entire month. Snow has accumulated several times and melted out at all elevations... Mid-November first accumulating snowfall that has remained in place fell at elevations above 5,500 feet. | |
| 2012-10-27 | 2012-10-27 | Steiner | First accumulating snow of the season on Canyon floor- 10cm. 34 degrees F. Intensity= S<1. Winds Calm. *Entirely melted out a few days later. |
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