GNFAC Avalanche Forecast for Fri Dec 20, 2024
This is Ian Hoyer with the avalanche forecast for Friday, December 20th, at 7:00 am. This information is sponsored by Klim and Cooke City Super 8/Bearclaw Bob’s. This forecast does not apply to operating ski areas.
There is no new snow. This morning, winds are moderate to strong out of the south and west (a bit lighter out of the northwest in Cooke City). Temperatures are in the 20s and 30s F.
Today, skies will be clear, winds moderate out of the southwest, with high temperatures in the 30s F.
It looks like there will be a dusting of snow tomorrow night with more chances for snowfall during the next work week.
Triggering, large, dangerous avalanches remains likely today on slopes steeper than 30 degrees.
The reports continue to flow in of avalanches that broke during the snow and wind events this week. New reports yesterday include:
- Many natural avalanches near Cooke City, in the Miller, Fischer and Sheep Creek drainages and another in the Goose Lake area that looks to have broken on the mid-pack weak layers. Both parties also reported numerous cracks/collapses while travelling yesterday.
- A natural on Fan Mountain, near Big Sky and another on Arden Peak, in Hyalite.
There are widespread weak layers of sugary, faceted snow buried about 1-2 feet deep (videos from this week in Cooke City, Island Park, Buck Ridge, and Beehive). These weak layers formed on top of the snowpack during the dry weather in the first two weeks of December. Persistent slab avalanches have been breaking on these weak layers this week (avalanche activity log). Faceted weak layers often remain easily triggered for a couple days after a loading event stops and we expect that to be true today. Slopes loaded or stiffened by the intense winds on Wednesday are likely to be the most easily triggered (with such intense winds, this will be many/most slopes).
Avalanche conditions will slowly improve, but we’re not there yet. The avalanche danger is CONSIDERABLE. For today - avoid slopes steeper than 30 degrees.
In the Bridger Range, triggering large avalanches is possible, but the weak layers are a bit stronger than elsewhere, so they won’t be quite as reactive. Yesterday, my partner and I found no signs of instability near the Throne, even while digging three pits to search for it, and felt comfortable tiptoeing into avalanche terrain (video). I’m extra skeptical of slopes that got heavily wind loaded on Wednesday, particularly because of a natural on Saddle Peak that broke 1-3 feet deep, and ran 1500 vertical feet (photos).
If you want to get into steeper terrain, start off with smaller slopes, slopes just steeper than 30 degrees, and ones that have good runouts below this in case you get surprised. Watch for signs of instability (cracking, collapsing, or poor test results) and be ready to quickly retreat to lower angled slopes if you find them.
The avalanche danger is MODERATE in the Bridger Range.
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