Regions
Northwest Coastal.
The storm track is aimed at the Northwest this week resulting in rising avalanche danger. Avoid avalanche terrain during periods of heavy loading from snow, rain or wind.
Weather Forecast
Synopsis: The storm track looks like it will be aimed squarely at the Northwest for the next few days bringing a series of frontal systems. Expect 10-20 cm of snow on Tuesday, another 25-40 cm (or mm) Tuesday night through Wednesday, and it keeps coming down on Thursday. We should see a warming trend with freezing levels around 1200-1400 m on Tuesday, and 1500-1600 m on Wednesday/Thursday. Winds should be consistently moderate or strong from the S-SW.
Avalanche Summary
Most of the recent reported activity was from the north of the region. Numerous explosive triggered size 1-2.5 slabs were reported on Saturday and Sunday. Many of these were on wind-loaded N-NE aspects around 1400-1500 m. There were also a few natural cornice falls which triggered 10 cm deep slabs below. It's likely that southern sections also experienced recent natural avalanche activity but poor weather may have prevented observations.
Snowpack Summary
Strong winds have redistributed recent storm snow into wind slabs, and rain has saturated the surface of the snowpack to around 1000 m. If temperatures cool, the snowpack below treeline may gain some strength. Above treeline, a buried rain crust and/or surface hoar layer is down about 50 cm. Observations of the strength at this interface have been limited. The November crust near the bottom of the snowpack is generally well bonded, but may still be reactive in areas with a shallow snowpack, or with a very heavy load.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.