Regions
Northwest Inland.
Warm alpine temperatures may result in unexpected large avalanches, especially on south-facing terrain.
Confidence
Fair - Freezing levels are uncertain
Weather Forecast
Saturday and Sunday: Dry or very light flurries, with alpine temperatures around -2C. Winds expected to be light southwesterly rising to moderate southeasterly. Monday: Clear with sunny spells. Temperatures below freezing at low elevations but alpine areas may see inversion conditions that will elevate temperatures to near zero.
Avalanche Summary
Small cornice releases that have so far not released slabs on slopes below were reported from Friday. A large nautral avalanche (size 3) was reported from the Hankin-Evelyn from last weekend on a NW aspect.
Snowpack Summary
I suspect pockets of wind slab behind ridges & ribs at alpine and treeline elevations. I also suspect storm slabs on steeper terrain, unsupported slopes, or convex rolls. Deeper in the snowpack is a layer of facets (sugary snow) which formed during the cold mid-January drought. The combination of newer, warmer, cohesive snow above a thin, weak, rotten snowpack is a bad combination.
Problems
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
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.