Regions
Northwest Coastal.
Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain for the entire period
Weather Forecast
Wednesday night/Thursday: Moderate to heavy snow (falling as rain for a time below about 900 m). Moderate to extreme SW winds. Freezing level 500 m, rising for a time to about 900m.Friday: Light snow. Moderate to strong S winds. Freezing level around 700m.Saturday: Light snow. Light winds. Freezing level dropping to valley floor.
Avalanche Summary
A few size 1 soft slabs were triggered by skiers at treeline on Tuesday.
Snowpack Summary
Strong winds created new wind slabs on a variety of slope aspects at treeline and above on Tuesday. Small surface hoar was also buried by 10-25 cm new snow. Further snowfall and wind will add to existing storm slab and wind slab problems. A rise in freezing level (aka rain) could rapidly weaken the snowpack below treeline.Old wind slabs are now buried on slopes lee to previous SW winds. Deeper in the upper snowpack, a crust, hard slab, and/or surface hoar interface exists, depending on aspect and elevation. One recent snowpack test near Shames resulted in a hard "pops" shear on the buried surface hoar, down around 60 cm at the time. Large cornices loom as a threat: they could act as triggers for avalanches on slopes below. Mid and lower snowpack layers are generally well settled and strong. The exception seems to be the Bear Pass area where basal facets are still reported.
Problems
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.