Avalanche danger is Low this morning, increasing to Moderate by late afternoon or evening, and will continue rising overnight. Watch for developing, sensitive wind slabs at higher elevations once snowfall reaches roughly 6". A lingering chance remains for triggering an older slab up to a couple feet thick on a few high, northerly slopes.
Shallow soft slabs will begin to form later today as new snow accumulates and is drifted by southwest to west winds. Expect reactive drifts to form below alpine ridgelines and in crossloaded gullies. Monitor storm totals, and if you see cracking in slabs large enough to knock you off your feet, consider the terrain consequences below you.
An example of a thin wind slab in a drifted gulley.
Older, denser slabs one to two feet linger on previously drifted, high-elevation northerly slopes. These are the same slopes that tend to look appealing for early-season turns: they catch more snow and have a smooth ground surface that preserves a connected weak layer. Collapsing or cracking, like this observation from Cinnamon, are clear signs you’ve found this problem.
A remotely triggered slab on the north side of Mt. Baldy on Nov 22. This slope held an old layer of weak snow from October's snowfall, buried beneath 1 to 2 feet of drifted snow.
After nearly two weeks of mostly dry weather, our shallow snowpack has faceted extensively. Unlike the October dry-spell layer—which was continuous on only a few, high northerly slopes—today’s weak layers are much more widespread (See observations from Ruby Range, Kebler to Gothic, and Brush Cr). Once new slabs form on these weak surfaces, expect sensitive conditions underfoot and the potential for natural releases.
Above treeline, we are expecting 4" to 10" of new snow before sunset, favoring the Northwest Mountains. With these modest totals, new snow instabilities should remain small and typically limited to snow-favored areas and wind-loaded slopes. By sunrise tomorrow, storm totals could reach 20" in the Ruby Range, producing thicker, more connected slabs in the alpine and expanding instabilities into wind-sheltered or less snow-favored areas. Track snowfall throughout the day to gauge how hazardous the new slabs are and choose terrain accordingly. If you’re traveling on one of the few slopes that held old October snow layers, evaluate if there's a thicker, older slab disguised beneath whatever new snow falls today.
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