Triggering a wind slab along ridgelines is possible today. Persistent slab avalanches with high consequences remain possible on upper elevation northern slopes. Incoming warm temperatures and rain may create wet snow avalanches at low elevations by late afternoon.
If you find poor snowpack structure or notice previous wind loading, avoid slopes over 35 degrees.
West winds over the past 48 hours have transported the new snow from Tuesday's storm into fresh wind slabs on east aspects. These slabs are isolated to higher elevation ridgelines and gullies.
Wind slabs can be identified by a smooth round appearance. Watch out for cracking and stay off upper elevation slopes over 35 degrees.
Triggering a persistent slab up to 5 feet deep is a possibility on north aspects at upper elevations. While unlikely, the consequences for an avalanche this size are high.
These avalanches are likely to fail on basal facets, especially in the comparatively shallow snowpack of the southern Swans.
Terrain management is the only way to avoid this problem. If you find faceted snow underneath a slab, a persistent slab is possible, and your best bet is to stick to slopes below 35 degrees. Avoid convex rollovers or shallow areas of the slab, as these are likely trigger points.
The 10 inches of new snow Tuesday created a sensitive storm slab at mid elevation. Observers Tuesday reported widespread cracking, collapsing, and avalanches. The sensitivity of this problem has likely decreased significantly since then, but even a small avalanche into a terrain trap will prove problematic.
Look out for cracking or collapsing in the new snow and avoid convexities and terrain traps.
(1/10/2023)
Widespread Cracking on slope below sled
Photo: Caleb Kesterke
After the quick hitting storm Monday and Tuesday, the weather has been mild for the past 48 hours. Relatively mild temperatures and light winds have given excellent skiing and riding conditions. Winds have been predominantly westerly since the storm, creating wind slabs on northeast through southeast aspects. These slabs are isolated to upper elevation terrain and ridgelines. Although nobody has reported human triggered activity on these slabs, natural avalanches in the Bitterroot show it is possible for skiers and riders to trigger a slide.
The Seeley Lake zone received the most snow Monday, and observers reported a touchy storm slab with avalanching on Tuesday. The sensitivity of this problem has decreased significantly since then, but the potential still exists for lingering storm slabs at mid elevation.
Across all zones, the persistent slab problem is improving, but the potential still exists for very consequential avalanches. Poor structure remains on north slopes with layers of facets depth hoar, mid pack facets, and facets around crusts. These weak layers still show propagation potential when they fail. While the likelihood of triggering one of these avalanches is low, the consequences are very high, and avalanches may break up to 5 feet deep. At middle and lower elevations with a thick Christmas melt freeze layer, there is much less potential to affect the weak layers below the crust. Take the time to dig in the snow and if you find a slab on top of weak sugary snow, stay off slopes over 35 degrees. Give persistent slab time to heal. Every day the snowpack is getting stronger, but it is not worry free yet.
Incoming weather will raise temperatures and bring the potential for low elevation rain today. This is more likely in the southern and central Bitterroot, where 6000’ temperatures may reach the low 40s combined with periods of sun and rain. At low elevations, there is not enough of a snowpack on the ground, but the potential exists for loose wet activity in sheltered areas with continuous snow. Stay off of slopes over 30 degrees, and be aware of what terrain is above you if you encounter rapid warming and unsupportable wet snow.
Now is a great time to get out and practice with your rescue equipment. If you are considering taking an avalanche course this winter, don’t hesitate, as courses are filling up fast. Check out the classes and events tab on the home page to find a course.
Please let us know what you are seeing out there by submitting an observation.
Ski and ride safe!
