New snow has formed soft slabs at upper elevations. A strong southeast flow system will bring more snow beginning late Thursday afternoon. Amounts are uncertain but accumulations of more than 30 cm by Friday morning may be possible in some areas.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain on Thursday
Weather Forecast
A strong southeast flow system will bring snowfall beginning late Thursday afternoon. Amounts are uncertain but accumulations of more than 30 cm by Friday morning may be possible in some areas.TONIGHT: Flurries. Accumulation trace. Ridge wind moderate, southwest. Temperature near -9. Freezing level lowering to valley bottom.THURSDAY: Snow increasing in the afternoon and overnight. Accumulation 20-30 + cm. Ridge wind light to moderate, southeast. Temperature near 0. Freezing level rising to 1400 m.FRIDAY: Mainly cloudy, flurries increasing overnight. Accumulation 2-10 cm. Ridge wind light, northeast. Temperature near -1. Freezing level 800 m.SATURDAY: Mainly cloudy, light flurries. Accumulation trace. Ridge wind light, northeast. Temperature near -3. Freezing level 700 m.
Avalanche Summary
Tuesday a size 2.5 natural storm slab, likely triggered by a cornice collapse, was reported on a northerly aspect in the alpine. Cornice collapses up to size 1.5 were also reported but did not produce slab releases on the slopes below.Numerous wind slabs up to size 2 and loose dry avalanches up to size 1.5 were reported from the Lizard Range on Monday running either naturally or triggered by skiers testing small slopes. Explosives triggered widespread storm slabs up to size 1.5 and size 2 results on northerly aspects. Crown depths typically ranged from 40-80 cm.
Snowpack Summary
New wind slabs are building as approximately 40-50 cm of light dry snow has fallen in recent days and is being moved around by moderate to strong westerly winds. This storm snow overlies various old surfaces including old hard wind slabs, crusts, facets and spotty surface hoar (for example February 14 surface hoar is now 50 to 70 cm below the surface).Deeper in the snowpack, the widespread mid-December weak layer sits about 200 cm deep. This consists of a crust, facets or surface hoar.Near the base of the snowpack, a crust/facet layer could be awoken from a thin-spot trigger point, or with a very large load like a cornice fall.
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.