Good morning. This is Alex Marienthal with the Gallatin National Forest Avalanche Advisory issued on Thursday, April 7, at 6:45 AM. Today’s advisory is sponsored by Yellowstone Arctic Yamaha and Yamaha Motor Corp in partnership with the Friends of the Avalanche Center. This advisory does not apply to operating ski areas.
Temperatures warmed to the mid-40s F yesterday and are in the high 20s to low 30s F this morning. Winds yesterday were out of the west-northwest at 30-40 mph with gusts in the 50s. Today will be sunny with wind at 5-15 mph and temperatures near 50 F this afternoon. Tonight and tomorrow will be the warmest part of the week.
Bridger Range Madison Range Gallatin Range
Lionhead area near West Yellowstone Cooke City
The snowpack presents a variety of avalanche problems as it transitions from winter to spring. Wet snow avalanches will be the primary concern today as above freezing temperatures and sunshine melt the snowpack. Wind slabs and persistent weak layers will also contribute to instability, and cornices will be large and susceptible to breaking.
Expect wet loose avalanches as temperatures rise today. These start from a point and fan out as they move downhill and entrain snow. Snowfall prior to yesterday provides an unconsolidated snow surface for these avalanches to grow large. They can easily sweep a skier away and be very harmful above cliffs, trees, or other terrain traps. Wet slab avalanches will also become more likely today. Point-release wet slides, growing pinwheels of snow, and sinking deeper than your boot in wet snow are signs to avoid steep slopes with a wet snow surface. Anticipate decreasing stability throughout the day, on sunny slopes and lower elevations. The wet snow avalanche danger will start LOW this morning and rise to CONSIDERABLE early this afternoon.
Strong winds yesterday and 4-8” of new snow since Monday formed wind slabs that will be possible to trigger. Anticipate these near high elevation ridgelines and avoid steep leeward slopes in high consequence terrain. Persistent weak layers are buried 2-4 feet deep on some slopes. Though not widespread, avalanches failed on deeper week layers earlier this week in the northern Bridger Range (photo1, photo2), and the Big Sky ski patrol reported a large avalanche on Fan Mountain. These lurking instabilities make the dry snow avalanche danger MODERATE today.
Cornices are large and can break farther back from the edge than expected. Above freezing temperatures will make them easy to trigger or fall naturally. Give these monsters a wide berth as you travel along ridgelines, and avoid slopes below them.
Our last advisory of the season is Sunday, April 10.
I 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.
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