Confidence
Fair - Intensity of incoming weather is uncertain on Sunday
Weather Forecast
Friday: An approaching warm front from the NW will bring light- moderate snow amounts up to 10 cm. Ridgetop winds moderate from the SW. Treeline temperature near -5. Freezing levels could rise to 800m. Saturday: Snow amounts up to 10 cm. Ridgetop winds moderate-strong from the SW. Treeline temperatures near -2. Freezing levels rising to 12-1500 m. Sunday: Cloudy, snow amounts 5-10 cm. Ridgetop winds moderate from the SW. Freezing levels should drop to 1000 m.
Avalanche Summary
Small size 1-1.5 natural avalanche activity occurred early Wednesday with arrival of new snow. Several reports of rider triggered size 1-2 avalanches occurred on Wednesday. They occurred on most aspects from 1500-2000m, the preserved stellar layer down 20-40 cm seemed to be the culprit. With forecast snow and wind, avalanche conditions will remain touchy, and susceptible to rider triggers through the forecast period.
Snowpack Summary
Due to changing winds, wind slabs can be found on N-NE aspects and S-SW aspects in the alpine on exposed slopes at treeline. A thin suncrust has formed on Southerly aspects; I suspect this may become more distinct after Thursday. Reports of a preserved stellar layer exist down 20-40 cm. This layer has been reactive to rider triggers and should remain on your radar. Up to 60cm sits over a variety of old surfaces. These include melt-freeze crusts at lower elevations, old sun crusts on Southerly aspects into alpine elevations and spotty areas of surface hoar in sheltered treeline areas. Where they exist, they may act as sliding layers. The mid and lower snowpack is well bonded 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.