Forecast snow through the day combined with moderate to strong wind will gradually raise the avalanche danger to considerable in the alpine on Wednesday
Confidence
Moderate - Intensity of incoming weather systems is uncertain on Wednesday
Weather Forecast
WEDNESDAY: Periods of snow, accumulation 10-15cm / Moderate to strong south wind / Alpine temperature -2 / Freezing level 1400mTHURSDAY: Flurries, accumulation 10-15cm / Moderate to strong south wind / Alpine temperature -4 / Freezing level 1300mFRIDAY: Snow, accumulation 15-20cm / Moderate southwest wind / Alpine temperature -3 / Freezing level 1300m
Avalanche Summary
Recent reports indicate both natural and human triggered wind slab avalanches in alpine and tree line lee terrain to size 1.5. On Wednesday, wind slabs may remain reactive to human triggers and at upper elevations the deeper mid-February weak layer continues to present a low likelihood of triggering yet would produce a large avalanche and thus a high consequence if triggered.
Snowpack Summary
Expect an additional 10-15cm of new snow through the day today to add to the 30 cm of storm snow from last weekend, which sits above a widespread rain crust up to 2200m. Thicker wind slabs and large cornices likely exist in alpine terrain. Reports suggest the storm snow is generally well bonded to the crust, and cooling temperatures should help stabilize the upper snowpack. The mid-February crust/facet layer is now 80-120 cm deep and may be up to 200 cm deep in wind loaded terrain. This layer was reactive prior to recent warming events, but now there's some uncertainty as to how long it will remain reactive.
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.