A wet and wild winter storm system with heavy snowfall, strong winds and mild temperatures is increasing the avalanche hazard. Travel in avalanche terrain is not recommend until the new snow has had a chance to settle and bond to the old surface.
Confidence
Moderate - Freezing levels are uncertain
Weather Forecast
TONIGHT: Snow. Accumulation 15-25 cm. Ridge wind extreme, southwest. Temperature near 0. Freezing level 1200 m.THURSDAY: Snow. Accumulation 20-30 cm. Ridge wind strong, southwest. Temperature near 0. Freezing level 1100 m.FRIDAY: Cloudy, flurries. Accumulation 10-15 cm. Ridge wind moderate, southwest. Temperature near 0. Freezing level 1000 m.SATURDAY: Cloudy, snow increasing. Accumulation 15-25 cm. Ridge wind light, southwest. Temperature -1. Freezing level 800 m.
Avalanche Summary
Tuesday, explosive control work and ski cutting produced numerous size 1-1.5 storm slab releases on leeward aspects at treeline and into the alpine, running on the January 15th crust. Expect this activity to increase as more snow and strong winds forecasted for Wednesday and Thursday.Warm alpine temperatures on Sunday produced numerous naturally triggered loose wet and wet slab avalanches mostly in the size 1-1.5 range, and a few up to size 2 on solar aspects.
Snowpack Summary
Above 1600 m elevation, 25-50 cm of new snow overlies the January 15th crust which exists on all aspects and elevations. This crust is thin on northerly aspects and up to 3 cm thick on solar aspects. Below this crust 30-40 cm of moist, well settled snow overlies the January 6th crust which is now buried 40-80 cm below the surface and exists up to about 2000m. Beneath the January 6 crust, the lower snowpack is generally strong and well settled. At lower elevation below treeline the new storm snow is wet and heavy with moist snow below.
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.