This is Ian Hoyer with the avalanche forecast for Friday, December 27th, at 7:00 a.m. sponsored by Klim and Cooke City Super 8/Bearclaw Bob’s. This forecast does not apply to operating ski areas.
An AVALANCHE WATCH has been issued from 5 a.m. today until 5 a.m. Saturday morning for the Island Park area, the Lionhead area, the southern Madison Range, and the southern Gallatin Range. Conditions are developing that will cause the avalanche danger to rise to HIGH this weekend. Heavy snowfall is expected to overload pre-existing weaknesses in the snowpack and create very dangerous avalanche conditions.
There are 5-7” of new snow (0.4-0.6” Snow Water Equivalent) across most of the advisory area, with only 3” in Hyalite. Winds are 15-25 mph out of the west, with gusts of 30-50 mph. Temperatures this morning are in the teens and 20s F.
Today, 3-5” of snow will fall in Island Park, with 1-3” across the rest of the advisory area. Winds will be 10-20 mph with gusts up to 30 mph out of the southwest. High temperatures will be in the 20s F.
An additional couple inches of snow are possible across the advisory area tonight. Snowfall will continue tomorrow and through the weekend.
Human triggered avalanches are LIKELY today. The weight of the new snow is overloading widespread weak layers buried 1-2 ft deep (Island Park video, Bacon Rind video, Bridgers video). Wind loaded slopes will have the deepest slabs of new snow and will be especially touchy, but slopes without wind effect could slide too.
Yesterday, we got reports of cracks shooting out up to 100 feet in the southern Madison Range with only 2” of new snow (observation). This is a clear indication that weak layers have been pushed right to their tipping point. I don’t expect widespread natural avalanching today - but if you get onto or even near a steep slope, expect to trigger a Persistent Slab avalanche.
Stick to slopes less than 30 degrees in steepness that aren’t below or connected to steeper slopes.
As the areas around Island Park and West Yellowstone continue to be favored for snowfall over the coming days, we expect the danger to rise in these areas this weekend.
For today, the avalanche danger is CONSIDERABLE.
Without as much new snow, triggering a slide isn’t quite as likely in the northern Gallatin Range. The same snowpack setup exists as elsewhere and large, dangerous Persistent Slab avalanches are possible, but the weak layers haven’t been loaded as heavily. Watch out for windloaded slopes where the new snow has been drifted into deeper slabs. Look for shooting cracks, collapses, or unstable test results as signs to avoid steep slopes.
The avalanche danger is MODERATE.
Upcoming Avalanche Education and Events
Our education calendar is full of awareness lectures and field courses. Check it out: Events and Education Calendar
Monday, December 30, 6-8 p.m., Free Avalanche Awareness and Conditions Update, MAP Brewing.
We offer Avalanche Fundamentals with Field Session courses targeted towards non-motorized travelers in January and one geared towards motorized users. Sign up early before they fill up.
Every weekend in Cooke City: Friday at The Antlers at 7 p.m., Free Avalanche Awareness and Current Conditions talk, and Saturday from 10 a.m.-2 p.m. at Round Lake Warming Hut, Free Rescue Practice.
Friends of the Avalanche Center: Fall Fundraiser!
We’re still counting on your support and the online Fall Powder Blast fundraiser is 80% of the way to our goal. Please consider making even a small donation HERE or via Venmo