Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain for the entire period
Weather Forecast
Friday night/Saturday: Extreme W winds easing to moderate overnight and switching to moderate to strong NW on Saturday. Moderate snowfall overnight, easing to light on Saturday. Alpine temperature around -10.Sunday: Strong W winds. Light snow. Alpine temperature around -7.Monday: Light SW winds. Light to moderate snow. Alpine temperature around -10.
Avalanche Summary
Loose dry avalanches (size 1) have been failing naturally and with skier traffic in steep terrain. I expect the size and frequency of avalanches has increased on Friday, and activity to continue through the weekend.
Snowpack Summary
By Saturday morning, I expect there might be up to 70 cm accumulated recent snow. Snowfall started light and dry this week, and may be easily shifted onto lee slopes by strong W to NW winds. New storm slabs, cornices and wind slabs are likely. Mostly this snow overlies loose dry surfaces, old wind slabs below ridge crests, and sun crusts on solar aspects. A surface hoar/facet/sun crust layer from mid February (12th) may be buried in the upper snowpack, but it has not been widely reported from this region. Mid and lower snowpack layers are generally well settled and stable.
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.