Good Morning. This is Eric Knoff with the Gallatin National Forest Avalanche Advisory issued on Friday, February 23rd at 7:00 a.m. Today’s advisory is sponsored by Swiss Fit Montana and Beartooth Powder Guides. This advisory does not apply to operating ski areas.
Over the past 24 hours the mountains near Big Sky picked up a trace to 1” of new snow. This morning, temps range from the single digits above or below zero F under mostly clear skies. Winds are light to moderate out of the S-SW. Today, clear and calm conditions will persist and highs will warm into the teens F. There is a slight chance for snow showers tonight and the mountains could see a trace to 2” by tomorrow morning.
The biggest concern in the mountains around Cooke City is wind loaded slopes. Winds have been relatively calm over the past 24 hours, but strong westerly winds caused significant loading earlier in the week. Wind loaded slopes in steep rocky terrain or below ridgelines will be the most prone to producing avalanches. Evaluate snow and terrain carefully and approach all steep, wind loaded slopes with caution.
Slides failing on a thin layer of facets 1.5-2’ deep are also possible. On Tuesday, this layer produced unstable results in stability tests on a south facing slope around 10,000 ft. (video). Look for and asses this thin layer of facets before committing to steeper slopes.
For today, wind-loading and buried weak layers make human triggered avalanches possible and the avalanche danger is rate MODERATE.
Wind slabs are the main concern in the mountains around Bozeman, Big Sky and West Yellowstone (video). Watch for rounded pillows of wind drifted snow below ridgelines, cliff bands or steep convex rolls (photo). The best way to mitigate the wind slab hazard is to avoid all wind loaded slopes steeper than 30 degrees. In addition to wind loaded slopes, cornices are an ever growing problem (photo). These bus sized chunks of snow can fail under the weight of a single person and can break farther back than you might expect. Give them a wide buffer along the ridgelines and limit exposure time on slopes below (photo).
Today, human triggered avalanches are possible on wind-loaded slopes which have a MODERATE avalanche danger. Non-wind loaded slopes have a LOW danger since the snowpack is generally stable.
If you get out and have any avalanche or snowpack observations to share, drop a line via our website, email (mtavalanche@gmail.com), phone (406-587-6984), or Instagram (#gnfacobs).
Upcoming Avalanche Education and Events
BOZEMAN
Feb. 28th, Know Before You Go avalanche awareness, 7:00 p.m. @ Procrastinator Theater, MSU
March 2nd and 3rd, SheJumps Companion Rescue Clinic, Info and Register HERE
March 2nd, Avalanche Awareness, 7-8:00 p.m., MAP Brewing Bozeman Split Fest
March 7th, Avalanche Awareness, 6-7:30 p.m. @ REI
DILLON
Feb. 24th and 25th, Snowmobile intro to avalanches w/ field course. More info: https://msuextension.org/conference/
COOKE CITY
Every Friday and Saturday, Current Conditions Update and Avalanche Rescue, Friday 6:30-7:30 p.m. at The Soda Butte Lodge in February. Saturday anytime between 10-2 @ Round Lake.
A snowmobiler was caught and killed in an avalanche in Idaho, near the Wyoming border north of Alpine on Tuesday, February 20. This is the 3rd avalanche in SE Idaho since the beginning of the year. The East Idaho News has a preliminary report.