Storm slabs will likely remain reactive with continued snow and wind. Continually assess for changing conditions, and stick to low-consequence terrain, while avoiding large avalanche paths and overhead hazards like cornices.
Problematic weak layers are becoming spotty across the region, however recent large persistent slab avalanche observations continue to trickle in reminding us that these layers remain a concern in this region. Recent avalanches have been triggered by a mix of large loads like cornices.
Continued snow and wind will build reactive storm slabs at all aspects and elevations.
A layer of large and weak facets sits near the base of the snowpack. This layer continues on a sporadic basis to produce very large avalanches that can travel far. Riders are most likely to trigger an avalanche on this layer in steep, shallow terrain, or by triggering a smaller avalanche that could step down to this layer. Cornices will continue to grow with new snow and wind and could be the large load needed to trigger deep persistent weak layers. Your best defense is to stay diligent in choosing low-consequence terrain away from overhead exposure.
Several storm and wind slab avalanches (sizes 1 to 2) were reported on Saturday, mostly in alpine terrain on a variety of aspects.
1 large, size 3.5, natural, deep persistent slab avalanche was observed in the western Purcells. This occurred in large alpine terrain at roughly 2750 m.
On Friday, a naturally triggered size 2 persistent slab that likely failed on a crust down around 100 cm was reported on a west aspect below treeline near Joss mountain.
Roughly 50 to 70 cm of new snow has fallen since late last week. The recent snow is settling into storm slabs that will be most reactive where either wind has stiffened the snow or they overlie a layer of recently buried surface hoar.
The mid-pack is generally well consolidated with a few operations reporting continued snowpack results on a spotty surface hoar layer down roughly 80 cm. Reports of large avalanches involving various layers of surface hoar/crusts and facets within the mid-pack depth are sporadic but are a reminder of the complicated snowpack across this region.
In the lower snowpack, a layer of large and weak facets from November near the base of the snowpack is slowly gaining strength but there continues to be low confidence in this layer. Large destructive avalanches are the result of this layer being triggered.
Sunday night
Cloudy and light snow, 2 to 7 cm. Moderate westerly alpine winds. Treeline temperature around -5 C.
Monday
Cloudy with snow, 5 to 10 cm. Light to moderate westerly alpine winds. Treeline temperatures 0 to -5 C.
Tuesday
Heavier snow begins Monday night into Tuesday, 10 to 25 cm. Light to moderate northeast alpine winds. Treeline temperatures dropping to around -15 C by day's end.
Wednesday
Cloudy with sunny periods, no precipitation. Light northeast alpine winds. Treeline temperatures -15 to -20 C.
More details can be found in the Mountain Weather Forecast.
