Good Morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Advisory issued on Saturday, March 25th at 7:00 a.m. Today’s advisory is sponsored by Grizzly Outfitters in partnership with The Friends of the Avalanche Center. This advisory does not apply to operating ski areas.
At 6 a.m. there’s rain in the valley and snow in the mountains. There is 4” of dense new snow in the Bridger Range, 2” near West Yellowstone, and 1” near Big Sky and Cooke City. Temperatures are high 20s and low 30s F with west to southwest wind at 15-25 mph. Temperatures will reach the low 30s F today then drop to the teens F tonight. Wind will be 5-15 mph out of the west to southwest in the southern ranges and northwest near Bozeman. Snow will taper off this morning with mostly cloudy skies today and scattered snow showers tonight. By tomorrow morning the mountains will get 3-5” of snow near Bozeman and Cooke City with 1-2” near Big Sky and West Yellowstone.
Bridger Range Madison Range Gallatin Range
Lionhead area near West Yellowstone Cooke City
Early morning snow showers urge an increase in avalanche danger today. The forecast is for light snow accumulations and calm wind, but the forecast could be wrong and just a few inches of snow will create small hazards. New snow will bond poorly to firm crusts and make loose avalanches easy to trigger. Small wind slabs could be found near ridgelines and have high consequences above cliffs or dense trees.
Yesterday, temperatures stayed relatively cool and allowed the snow surface to stay frozen and supportable after two nights of solid freeze. We went to take down the Hyalite weather station and found thick, supportable crusts on high elevation slopes through early afternoon (video). Ski patrols at Bridger Bowl and Big Sky were similarly satisfied with strong, supportable surface conditions through the day. Freezing temperatures last night and clear skies prior to early morning snow allowed the snow surface to again refreeze.
Today, cool temperatures and cloudy skies make wet avalanches deeper than the new snow unlikely. If the sun peeks out for just a few minutes or where temperatures are warmer (e.g., lower elevations) the new snow could get moist, and wet loose avalanches could run naturally or be easily triggered. Be aware of natural dry or wet loose avalanches from steep terrain overhead. I have been surprised more than once by small, but potentially high consequence sluffs during quickly changing spring conditions. The avalanche danger today is MODERATE.
Last week, skiers near Cooke City observed some deeper dry slab avalanches on north aspects (photo) and a group triggered two wind slabs on an east aspect. These deeper dry slabs are not widespread, but possible on shady high elevation slopes.
CORNICE DANGER
Cornices are extra big this year (photo) and warm temperatures weaken their grip on the ridgelines. They can break far from the edge and can trigger large avalanches like one observed last week in the Bridger Range (photo).
I will issue the next advisory tomorrow morning by 7:30 a.m.
We rely on your field observations. Send us an email with simple weather and snowpack information along the lines of what you might share with your friends: How much new snow? Was the skiing/riding any good? Did you see any avalanches or signs of instability? Was snow blowing at the ridgelines? If you have snowpit or test data we'll take that too, but this core info is super helpful! Email us at mtavalanche@gmail.com or leave a message at 406-587-6984.