Regions
Northwest Inland.
Avalanche danger may spike to HIGH on Tuesday if strong winds continue.
Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain for the entire period
Weather Forecast
Monday night: Expect winds of up to 90 km/h from the SW and about 15 cm of snow overnight. Alpine temp -6.Tuesday: Westerly winds dropping to moderate. Alpine temp -8. Light snow. Freezing level 600 m, dropping to 200 m overnight.Wed: Light NW winds. Alpine temp -8. Freezing level at surface. Light to moderate snow.Thurs: Moderate SW winds. Alpine temp -5. Freezing level 400 m. 8-10 cm snow.
Avalanche Summary
Strong W-NW winds triggered a natural avalanche cycle on Sunday, with several slabs to size 2 failing behind cross-loaded ribs and gullies. A size 2.5 slab from the headwall above the Hankin area uptrack is suspected to have failed on the Nov crust/facet layer.
Snowpack Summary
Storm snow has been redistributed by very strong W-NW winds, creating touchy wind slabs on a variety of slopes, even below treeline. In the upper snowpack, surface hoar is buried at tree line in isolated sheltered areas. A November crust/facet layer near the base of the snowpack has the potential for deep releases. Snow depths are highly variable due to the influence of recent winds.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.