This is Alex Marienthal with the avalanche forecast for Sunday, December 22nd, at 7:00 am. This information is sponsored by World Boards and Spark R&D. This forecast does not apply to operating ski areas.
This morning there is 1-2” of new snow near Bozeman, Big Sky and Cooke City. Temperatures are low 20s to 30 F. Overnight, wind from the southwest and west increased to 10-30 mph with gusts of 30-55 mph.
Today, skies will be mostly sunny near Bozeman and Big Sky with clouds and light snow elsewhere. Temperatures will be in the 20s to low 30s F with wind out of the west decreasing to 10-20 mph. Tonight cloud cover will increase throughout the forecast area with 1” of snow possible by morning and 2-4” more through tomorrow.
All Regions
Today a person can trigger large persistent slab avalanches that break on weak layers buried in the middle of the snowpack or near the ground. These persistent slab avalanches have become less likely since snowfall and strong winds ended late Wednesday, but the potential size and consequences remain large.
During the first half of this week strong winds drifted new snow into thick, heavy slabs (Beehive video). On Wednesday there were multiple large natural avalanches near Cooke City (video, Henderson photo, Fisher photo), and an avalanche on Saddle Peak broke 1-3 feet deep (photos). On Tuesday Ian triggered an avalanche remotely (from lower angle terrain nearby) on Buck Ridge near Big Sky (details), and on Friday a skier had a large collapse in the Bridger Range (observation).
Choose small, simple, non-wind-loaded slopes with clean runouts free of hazards like rocks, trees or cliffs. If you have any doubts about snowpack stability avoid slopes steeper than 30 degrees and be cautious of runout zones below.
Yesterday on Buck Ridge a snowmobiler triggered a 12” deep wind slab avalanche (photo). Strong winds last night might have formed fresh wind slabs, and a few potentially unstable drifts could remain from earlier in the week. Look for signs of wind-drifted snow and be cautious of wind-loaded slopes, especially where consequences of a slide are higher due to terrain traps.
Carefully and continuously assess the snowpack and terrain for avalanche potential, and travel one person at a time on steep slopes or through runouts. The avalanche danger is MODERATE.
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