A natural avalanche cycle is occurring in Rogers Pass. Today is a great day to stay in the trees with no overhead hazard, or better yet, maybe head to the ski hill...
Weather Forecast
The cold front has passed through the area, and in its wake we should see unsettled conditions. Expect flurries, moderate W winds in the alpine, and freezing levels around 900m. By the weekend, skies should clear, temp's will likely drop, and the winds will shift to a more northerly flow.
Snowpack Summary
We received 40-50cm of storm snow in the last 24hrs in the alpine. Accompanying this were mild temp's and strong winds from the W, creating very touchy storm slabs. Although this fell on a generally settled snowpack, the Dec 8 and Nov 28 surface hoar/facet layers remain a concern. Avalanches could step-down to these layers with the new loading.
Avalanche Summary
Avalanche control last night produced significant results, with numerous size 3-3.5's from Mount's Tupper and MacDonald. A possible size 4 from Tupper cleared out mature timber and deposited it on the road. Needless to say, this is likely happening in the backcountry as well.
Confidence
Due to the number and quality of field observations
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.