Wind slabs may exist below ridgecrest on leeward slopes and loose-dry sloughing may be easily triggered from steeper terrain features.
Be mindful of the lingering deep persistent slab problem. Caution on shallow snowpack areas and thin to thick steep rocky zones.
The new snow from Tuesday's storm accompanied by strong winds and slight warming on Thursday may form new and reactive wind slabs. They could have a poor bond to the crusty snow surfaces below.
Dry loose sloughing may be seen from steeper slopes and terrain features.
The early December crust can be found 80-150 cm deep. A deep persistent slab problem has created a low likelihood, high consequence scenario that is difficult to forecast. There was an increase in avalanche reports on this layer last weekend due to warming in the adjacent Flathead-Lizard Region. This is a complex problem so our best advice is to avoid likely trigger spots such as steep, rocky unsupportive slopes with a shallow or thin to thick snowpack.
Thursday Night: Increasing cloud cover later in the evening with isolated flurries. Ridgetop wind light from the southwest and alpine temperatures near -10.
Thursday: Mix of sun and cloud. Moderate ridgetop wind from the southwest. Alpine temperatures warming to near -5 and freezing levels valley bottom.
Friday: Mix of sun and cloud. Ridgetop wind light from the West. Alpine temperatures near -5 and freezing levels valley bottom.
Saturday: Potential for inversion with valley cloud and cooler temperatures down low and sunshine in the alpine. Alpine temperatures near -3 and below freezing in the valleys.
No new reports by Wednesday afternoon.
Recent deep persistent slab avalanches were reported in neighboring regions (Lizard-Flathead and Waterton National Park) over the last few days. These human-triggered and natural avalanches failed on the early December crust and showed wide propagation. This evidence suggests the deep persistent slab problem is still a concern in the region.
The region received up to 25 cm by Tuesday, which now overlies older surfaces like hard wind slabs or a recent melt-freeze crust. The crust varies from thin/breakable to thick/supportive, according to the aspects and elevation. Under it, the snowpack consists of a variety of old surfaces, including soft snow in sheltered areas and wind slabs in exposed and open areas.
The most notable layer of concern in the snowpack is a crust that was formed in early December and is now typically down 80-150 cm. In the neighboring Lizard-Flathead region, three very large avalanches were reported on this layer on January 13. This layer has created a tricky low likelihood, high consequence scenario which is best managed through conservative terrain choices and disciplined backcountry travel techniques.
