Confidence
Fair - Intensity of incoming weather is uncertain
Weather Forecast
Another frontal system tracking inland from the NW Coast will bring unsettled conditions accompanied by light-moderate precipitation. Thursday: Mainly dry conditions with a mix of sun and cloud. Ridgetop winds moderate from the SW. Treeline temperatures near -3. Freezing levels 1500 m. Friday: Snow amounts moderate accumulating 15 cm. Ridgetop winds light-moderate from the SW. Freezing levels 1000 m, falling to valley bottom overnight. Saturday: Light snow amounts. Ridgetop winds L-M from the SW. Freezing levels near 1000 m.
Avalanche Summary
A widespread natural cycle occurred on Monday, operators reported numerous size 2-3.5 natural avalanches, starting in the alpine on all aspects and most elevations.. A minor natural cycle up to size 3 in the Alpine occurred Tuesday. Rider triggered slabs were also reported in the size 1-2 range, failing within storm snow instabilities. I suspect conditions will still remain touchy, and unpredictable. With more forecast snow, wind and warming the avalanche danger will elevate.
Snowpack Summary
The weekend past, 60-100 cm snow has fallen. Strong winds and fluctuating temperatures have created storm slabs and wind slabs on a widespread basis. Persistent weak layers (surface hoar, facets, crusts) buried in February are a concern at all elevations and could be triggered by storm slabs, wind slabs, or the additional load of a sled/skier. Avalanches may be unexpectedly large, and destructive. If the sun shines, watch for snowpack deterioration on solar aspects. Large cornices have formed, and may act as a potential trigger on slopes below. They could step down to the persistent weakness.
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.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.