Archived Advisories

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Snowpack and Avalanche Discussion Attached images Attached Videos
Jan 20, 2017 - Eric Knoff
Madison Range   Gallatin Range  Lionhead area near West Yellowstone   Cooke CityThe snowpack has two distinct weak layers capable of producing avalanches. One exists mid-pack and the other near the ground. The lack of snow over the past week combined with warmer temperatures have helped these weak layers gain strength. On Wednesday, Doug got stable results in three different snowpits in the Lionhead...
Bridger West Side
Goat triggered avalanche in Hyalite
Avalanche in Beehive 4 - Jan 15
Jan 19, 2017 - Eric Knoff
Madison Range   Gallatin Range  Lionhead area near West Yellowstone   Cooke CityIt has been nearly a week since the last significant snowfall and avalanches are becoming harder to trigger. Yesterday, Doug and his partner rode in the Lionhead area near West Yellowstone and dug multiple snowpits. Each pit pointed towards improving stability (video). Although the backcountry snowpack is getting...
Avalanche near Divide Peak
Goat triggered avalanche in Hyalite
Avalanche in Beehive 4 - Jan 15
Jan 18, 2017 - Doug Chabot
Madison Range   Gallatin Range   Lionhead area near West Yellowstone   Cooke CitySouth of Bozeman to Big Sky, West Yellowstone and Cooke City, the snowpack has 2 weak layers responsible for avalanches, collapsing and poor stability test scores (snowpits). One layer is on the ground and the other formed at the surface before the last snowstorm ended 6 days ago. Since then, the likelihood of...
YNP: small avalanche on Druid Peak
Avalanche near Divide Peak
Goat triggered avalanche in Hyalite
Beehive Avalanche Overview
Jan 17, 2017 - Doug Chabot
Madison Range   Gallatin Range   Lionhead area near West Yellowstone   Cooke CityThe snowpack has two weak layers of sugary facets: a thin layer formed during the cold weather 10 days ago and a thick layer at the ground. Yesterday, Alex and I skied into Beehive Basin north of Big Sky to look at the natural avalanche that occurred Sunday afternoon (video, photo). A small, wet loose avalanche likely...
YNP: small avalanche on Druid Peak
Avalanche near Divide Peak
Goat triggered avalanche in Hyalite
Beehive Avalanche Overview
Jan 16, 2017 - Alex Marienthal
Cooke City   Madison Range   Southern Gallatin Range  Lionhead area near West YellowstoneSince the storm four days ago avalanches have become less likely, but remain possible. The mountains near Big Sky, West Yellowstone, and Cooke City have two buried weak layers. A layer of sugary snow near the ground, and a layer of facets that formed near the surface before last week’s storm. Large...
Avalanche in Beehive 3 - Jan 15
Avalanche on Sheep Mtn. near Cooke
Taylor Fork Snowpit - Jan 13 2017
Remotely triggered slides - Lionhead
Jan 15, 2017 - Alex Marienthal
Cooke City   Madison Range   Southern Gallatin Range  Lionhead area near West YellowstoneOver the last three days the mountains have not received any new snow and wind has been light. Without recent loading the snowpack has adjusted to the weight of last week’s storm. However, weak facets below 2-4 feet of recent snow make large avalanches possible to trigger. An avalanche observed...
Unstable extended column test at Lionhead
Avalanche on Sheep Mtn. near Cooke
Natural Avalanche Cooke City
Remotely triggered slides - Lionhead
Jan 14, 2017 - Eric Knoff
Cooke CityThe snowpack around Cooke City is still adjusting to the 3+ feet of snow that fell earlier in the week. Natural avalanches occurred during and immediately after the storm - many of these propagated long distances and ran full track (photo, photo, video). These slides likely failed on a layer of near surface facets that formed prior to the storm during the extended period of cold weather.While natural avalanche activity...
Taylor Fork Snowpit - Jan 13 2017
Natural Avalanche Cooke City
Remotely triggered slides - Lionhead
Natural avalanche near Lulu Pass
Jan 13, 2017 - Eric Knoff
Cooke CityAfter the biggest storm of the year, the snowpack is getting a break. It has been over 24 hours since the snow stopped and winds have diminished significantly. Without active loading, natural avalanches are less of a concern, but human triggered avalanches remain likely. A large natural avalanche on the SE face of Scotch Bonnet two days ago is a good reminder of what’s still possible (photo, video).Slides failing...
Natural avalanche near Lulu Pass
Snowpit showing weak layer depth
Jan 12, 2017 - Doug Chabot
Cooke CityThe avalanche warning has expired with the snowstorm. Since Sunday night the mountains got 4’ of snow (3.5” of SWE) with strong winds that blew at all elevations. Avalanches released naturally on a thin layer of facets underneath the new snow. I was in Cooke City and made a video showing this layer breaking in my tests. Yesterday morning I awoke to 2’ of new snow. My partner and I pinned our...
Standing on the toe of debris
A panorama of the avalanche near Lulu Pass
Natural avalanche near Lulu Pass
Snowpit showing weak layer depth
Jan 11, 2017 - Eric Knoff
Cooke CityOnce again Cooke City is in a league of its own. Over the past 72 hours this area has received nearly 3”of SWE (snow water equivalent) totaling roughly 3 feet of snow. This heavy load has been deposited on a weak-old snow surface that formed during the cold snap last week. Yesterday, Doug got fractures to propagate easily in his stability tests on the new snow/old snow interface (video). This is an obvious sign...
Jan 10, 2017 - Doug Chabot
Cooke CityCooke City has an Avalanche Warning. In the last 48 hours the mountains have gotten 2.5” of snow water equivalent (SWE), estimated to be over 2’ of snowfall. Last week’s cold weather formed a weak layer at the surface which is now buried and unstable from the weight of the new snow. Strong winds also formed thick wind drifts adding even more weight. Avalanches will occur naturally and it is...
Jan 9, 2017 - Alex Marienthal
Cooke CityThe mountains near Cooke City got 1.4” of snow water equivalent (SWE) overnight, in addition to .4” of SWE the night before. This heavy snow fell on a faceted, weak snow surface, and strong winds formed deep drifts of snow over this weak layer. Avalanches breaking below the new snow and fresh wind slabs are likely and will run naturally today. Weak facets near the ground are also a concern and large...
Avalanche crown in first Yellowmule on Buck Ridge
Wind slabs breaking
Forecasters Social
Jan 8, 2017 - Alex Marienthal
Cooke City   Madison Range   Southern Gallatin Range Lionhead area near West YellowstoneNew snow and strong wind formed fresh wind slabs overnight. These slabs rest over weak snow near the surface of the snowpack, and add weight over weak layers near the base of the snowpack. I found weak snow throughout the snowpack at Buck Ridge on Friday (video). Weak snow formed near the surface of the snowpack...
Avalanche crown in first Yellowmule on Buck Ridge
Avalanche in first Yellowmule on Buck Ridge
Natural Avalanche up Republic Creek - Cooke City
Natural Avalanche on Sheep mtn. near Cooke City
Jan 7, 2017 - Alex Marienthal
Bridger Range   Madison Range   Gallatin Range   Lionhead area near West Yellowstone   Cooke CityThe snowpack throughout the advisory area has multiple layers of weak sugary snow. Yesterday at Buck Ridge we found a weak snowpack and saw evidence of avalanches that broke on facets near the ground within the past week (video). Weak facets at the base of the snowpack are buried by 2-6...
Avalanche crown in first Yellowmule on Buck Ridge
Avalanche in first Yellowmule on Buck Ridge
Wind slabs breaking
Forecasters Social
Jan 6, 2017 - Eric Knoff
Bridger Range   Madison Range   Gallatin Range   Lionhead area near West Yellowstone   Cooke CityWeather is the architect of avalanches. Although little snow has fallen over the past week, strong winds have formed small but touchy wind slabs in isolated areas. Yesterday, Alex and I experienced these touchy conditions first hand while skiing around Bridger Bowl. We observed two small natural...
Jan 5, 2017 - Eric Knoff
Bridger Range   Madison Range   Gallatin Range   Lionhead area near West Yellowstone   Cooke CityCold, dry weather is helping to create a weaker snowpack. But without new snow, avalanches are becoming harder to trigger.There are, however, a few avalanche concerns. Strong winds out of N-NE yesterday afternoon developed fresh wind slabs on upper elevation, leeward slopes.  These slabs...
Cooke City:it's never simple
Jan 4, 2017 - Doug Chabot
Bridger Range   Madison Range   Gallatin Range   Lionhead area near West Yellowstone   Cooke CityIn the last 48 hours the likelihood of triggering an avalanche has decreased. Our last substantial snowfall was on Friday and winds have calmed since Sunday. In the absence of finding fresh avalanches or collapsing or cracking as we travel, we lean on snowpits and tests to gather stability data...
Marty's Snowpit Profile
Cooke City:it's never simple
Jan 3, 2017 - Doug Chabot
Bridger Range   Madison Range   Gallatin Range   Lionhead area near West Yellowstone   Cooke CityEvery time it snows we get naturally occurring avalanches, the number one sign of instability. Right now, without much snow or wind-loading, avalanches are becoming rare and we rely on stability tests and red flags of cracking and collapsing to help determine stability. Yesterday in the Bridger...
Wind slabs breaking
Cooke City:it's never simple
Jan 2, 2017 - Alex Marienthal
Bridger Range   Madison Range   Gallatin Range   Cooke CityLionhead area near West Yellowstone  Throughout the advisory area layers of sugary weak snow form the foundation of the snowpack. Slabs of snow 3-7 feet thick rest over these weak layers, which broke and caused large avalanches through December. A natural avalanche was observed yesterday in the Northern Gallatin Range. Last...
Natural Avalanche up Republic Creek - Cooke City
Natural Avalanche on Sheep mtn. near Cooke City
Natural Avalanche near Cooke, north of Sheep mtn.
Jan 1, 2017 - Alex Marienthal
Bridger Range   Madison Range   Gallatin Range   Cooke City Lionhead area near West Yellowstone      Throughout the advisory area there are layers of weak faceted snow near the ground. These layers sit above thick ice crusts at the base of the snowpack on some slopes, and sit directly on the ground on other slopes. Either way, these sugary weak layers have the potential...
Deep snowpack - Cooke City
Natural Avalanche up Republic Creek - Cooke City
Natural Avalanche on Sheep mtn. near Cooke City
Natural Avalanche near Cooke, north of Sheep mtn.
Dec 31, 2016 - Eric Knoff
Madison Range   Southern Gallatin Range   Lionhead area near West Yellowstone   Cooke CityThere’s a high level of spatial variability in the snowpack. Some slopes are stable while others are not. The most significant factor creating unstable conditions is wind deposited snow. Earlier in the week, strong winds out of the W-SW formed dense wind drifts on leeward slopes. These drifts added a...
Deep snowpack - Cooke City
Natural Avalanche up Republic Creek - Cooke City
Natural Avalanche on Sheep mtn. near Cooke City
Dec 30, 2016 - Eric Knoff
Madison Range   Southern Gallatin Range   Lionhead area near West Yellowstone   Cooke CityRecent avalanche activity has one thing in common – avalanches are occurring on wind loaded slopes. Yesterday, Alex was in Cooke City and observed multiple large natural avalanches that took place over the past few days. Other skiers in the area also observed recent natural activity. Most slides are...
Natural Avalanche up Republic Creek - Cooke City
Large cornice chunk in debris pile
Dec 30, 2016 - Eric Knoff
Madison Range   Southern Gallatin Range   Lionhead area near West Yellowstone   Cooke CityRecent avalanche activity has one thing in common – avalanches are occurring on wind loaded slopes. Yesterday, Alex was in Cooke City and observed multiple large natural avalanches that took place over the past few days (photo). Other skiers in the area also observed recent natural activity. Most slides...
Natural Avalanche up Republic Creek - Cooke City
Large cornice chunk in debris pile
Natural Avalanche on Sheep mtn. near Cooke City
Dec 29, 2016 - Eric Knoff
Madison Range   Southern Gallatin Range   Lionhead area near West Yellowstone   Cooke CityToday, wind slabs will be the primary avalanche concern in the mountains around Big Sky, West Yellowstone and Cooke City. Strong winds out of the W-NW yesterday combined with a foot of low density snow Tuesday night created perfect conditions for wind slab development. Thick wind drifts will be widespread on...
Blowing snow
Wind Ripples
Depth Hoar at Bacon Rind
Dec 28, 2016 - Doug Chabot
Madison Range   Southern Gallatin Range   Lionhead area near West Yellowstone   Cooke CityThe mountains around Big Sky to Lionhead to Cooke City all received about .5” of snow water equivalent (SWE). This translates into 8-12” of low density powder. I am concerned about the weight of the new snow and wind-loading. This .5” of SWE is in addition to the 1” of SWE that fell...
Blowing snow
Wind Ripples
Depth Hoar at Bacon Rind
Dec 27, 2016 - Doug Chabot
Bridger Range   Gallatin Range   Madison Range   Lionhead area near West Yellowstone  Southwest Montana’s snowpack has more similarities than differences. We are finding weak, sugary facets at the ground. The snow is not very supportable and you will sink to the dirt if you step out of your skis. Snowmobiles, especially short tracks, will dive into the facets on a hard turn. Both of...
Blowing snow
Wind Ripples
Depth Hoar at Bacon Rind
Dec 26, 2016 - Alex Marienthal
Bridger Range   Gallatin Range   Madison Range   Lionhead area near West Yellowstone  Yesterday’s 4-6” of snow totaled .2-.3” of snow water equivalent (SWE). Wind readily transported this low density powder into soft wind slabs. These wind slabs were easily triggered by skiers yesterday, and they will be deeper and remain easy to trigger today. Be cautious of...
Depth Hoar at Bacon Rind
Natural Avalanche Woody Ridge  - Cooke City
Natural Avalanche Woody Ridge - Cooke City
Natural Avalanche The Fin - Cooke City
Dec 25, 2016 - Alex Marienthal
Southern Madison Range   Southern Gallatin Range  Lionhead area near West YellowstoneOver the last 48 hours the mountains south of Big Sky and near West Yellowstone received 6-8” of snow equal to .8” of snow water equivalent (SWE). Moderate southeast wind yesterday formed drifts of snow over a weak snowpack. These wind slabs could be up to a foot thick and carry a skier or rider into...
Natural Avalanche Woody Ridge  - Cooke City
Natural Avalanche Woody Ridge - Cooke City
Natural Avalanche The Fin - Cooke City