Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Saturday, March 26, at 6:45 AM. Today’s advisory is sponsored by Mystery Ranch and Spark R&D. This advisory does not apply to operating ski areas.
A trace to one inch of snow fell yesterday morning with west winds blowing 10-20 mph at the ridge lines. This morning, under clear skies, temperatures are in the teens and winds are light at 5-10 mph out of the west. Today will be sunny, calm and temperatures will reach the low 40s. Another storm is forecasted Sunday night into Monday which should bring more snow to the mountains.
WET AVALANCHE DANGER
The mountains have loads of fresh, powdery snow that will moisten in today’s sunshine creating wet snow avalanche danger. Loose, wet, point release slides will occur on most slopes that get sun. Mountain temperatures will rise to above freezing and by early afternoon the upper few inches of the snowpack will get wet, loose cohesion and slide. Roller balls of snow that grow into ever expanding pinwheels is a sign the snow is getting primed to avalanche. Loose, wet avalanches can easily sweep you into terrain traps. For today, the loose, wet snow avalanche danger will rise to CONSIDERABLE on slopes getting sun, most notably south and east facing.
Southern Madison Range Southern Gallatin Range
Lionhead area near West Yellowstone Cooke City
The southern mountains have gotten 12-18” of snow since Tuesday (.8-1.5” SWE). Westerly winds loaded slopes at the ridgelines and over the last couple day’s this windblown snow is becoming harder, but not impossible, to trigger. Another avalanche concern, a weak layer of facets, is buried 2-3 feet down. This layer is hard to see with the naked eye, but pops out in stability tests. I found it in Taylor Fork last week (video) and Cooke City had numerous avalanches on this layer too (photos). It is not on all slopes, just some, which means digging and testing is the only reliable method of locating it. Although wet avalanche activity will take precedent on sunny slopes today, dry snow avalanches are still a threat and slopes are rated MODERATE.
Bridger Range Northern Madison Range Northern Gallatin Range
The northern mountains have received up to 2 feet of snow since Tuesday with Hyalite getting 30+”. Wind slabs at the ridgelines have become harder to trigger in the last two days. The snowpack is strong and deep (4-6’) and todays avalanche concern lies within the storm snow. Alex found this instability (ECTP 14) in Hyalite yesterday (video) which mimicked our findings on Buck Ridge (video) and on the Throne in the northern Bridger Range (video). This instability will be short lived, but worth testing for. Yesterday, skiers backed off a line near Fairy Lake when they got a column to break clean in their compression test. For today, besides an increase in wet, loose snow avalanches on sunny slopes, the dry snow avalanche danger is rated MODERATE on slopes that have been wind-loaded or steeper than 35 degrees. Lower angled terrain has a LOW danger.
Eric will issue the next advisory tomorrow morning by 7:30 a.m. If you have any snowpack or avalanche observations to share, drop us a line at mtavalanche@gmail.com or leave a message at 587-6984.