New snow and strong wind may form reactive wind slabs at upper elevations. They may be easily triggered due to the old weak snow surfaces they have formed on.
10 to 20 cm of new snow accompanied by strong forecast northwest wind may form fresh wind slabs on Thursday. Sensitivity could be greater in areas where storm and wind slab has formed over a crust, facets, or surface hoar.
Loose-dry sloughing may be seen on steeper terrain features in the alpine/ treeline where the new snow falls on a crust.
The mid-January surface hoar layer is a developing problem that could start to produce more avalanches in the future with increased load and slab development above. Use extra caution in sheltered terrain at treeline where preserved surface hoar is more likely to exist.
The early January facet layer is now down as deep as 80cm and might require a large load such as a cornice fall or a smaller avalanche in the layers above in order to be triggered. This problem is likely most concerning on high north and east facing terrain.
Low confidence in snowfall amounts on Thursday as there may be some enhancement due to the timing of the strong NW flow and the approaching warm front.
Wednesday Night: 5 to 10 cm of new snow and strong westerly winds at ridgetop. Alpine temperatures near -4 and freeing level at valley bottom.
Thursday: 5-10 cm through the day. Alpine temperatures near -1 and freezing levels 1500 m. Ridgetop winds will be strong from the West.
Friday: Mix of sun and cloud with light snowfall amounts. Alpine temperatures near -5 and freezing levels drop to 1000 m.
Saturday: Mix of sun and cloud. Alpine temperatures near -5 and freezing levels valley bottom. Ridgetop wind strong from the West.
No new avalanches were reported on Wednesday.
Another 5-15 cm and strong wind from the SW may build reactive wind slabs and soft slabs on Thursday.
Up to 20 cm of recent snow has fallen over a variety of surfaces including facets, surface hoar, and old wind slab. The new snow will likely not bond well to these surfaces. In the southern part of the region, it is possible to find a rain crust up to 1500 m.
Below this we have two persistent weak layers, the first is a surface hoar layer from mid-January buried down 20 to 30cm. The second is a layer of facets from early January which is now down 50 to 80cm, it has been most reactive where wind slab has formed above it and will now likely require a large load to trigger.
