Deep persistent slabs have become more trigger-able with the recent warming. The November rain crust will be a problem for some time to come. Keep an eye on the approaching warm, windy and wet storm.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Warm and windy for the next few days. Tuesday will see alpine temperatures climbing to -2 celsius with light flurries and SW winds over 100km/h. Wednesday will be similar with more precipitation in the forecast. Unfortunately some of the precipitation may fall as rain below 2100m.
Avalanche Summary
Nothing new.
Snowpack Summary
Surface hoar was observed in sheltered areas today. Recent warm temperatures have settled the snowpack creating a more cohesive slab above the November rain crust at treeline and below. Alpine areas are widely wind effected with widespread wind slabs. A layer of facets above the November rain crust is producing consistent moderate shears in snowpack stability tests. Test profile today at 2300m on a SE aspect on a 30 degree slope produced moderate Compression Tests and moderate Extended Column Tests down 65 to 70cm in the facets above the November crust.
Problems
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.
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.