Confidence
Fair - Timing of incoming weather is uncertain
Weather Forecast
A series of frontal systems will continue to affect the region over the next few days. In general, expect 15-20cm of snow each 12 hour period, with moderate to strong W-SW winds, and fluctuating freezing levels (FL). Tuesday: 15-30cm, heaviest in the evening/overnight. Strong SW winds, rising overnight. FL around 800-1000m gradually rising. Wednesday: 20-30cm, heaviest overnight. Strong W-SW winds. FL rising to 1600m. Thursday: 15-25cm. Strong SW winds. FL lowering to 1000m.
Avalanche Summary
Fresh wind slabs and cornices may be sensitive to human-triggers and the likelihood of natural activity will increase with the forecast weather.
Snowpack Summary
Wind-exposed slopes are predominately scoured and pressed, with pockets of wind slab from 20 to 50cm deep on North to East aspects at treeline and in the alpine.This new storm snow overlies a weak rain crust that formed last weekend. This crust extends to treeline elevations and overlies buried surface hoar and/or facets 10cm below. Generally speaking, confidence in this interface is growing, especially since it has'nt seen a significant load at the elevations where it exists. In the alpine where the crust does not exist, a stiffer wind slab may over-ride surface facets that formed during the early December dry spell. Persistent weaknesses seem to be less of a concern in the Cascades (Coquihalla and Allison Pass).The mid and lower snowpack are generally well-settled and strong.
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.