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Weather Forecast
A strong push of Arctic air will pass through Rogers Pass today. Expect winds to increase from the N, with temp's dropping into the minus teens. Skies should clear late in the day and into tomorrow. By Thursday, strong inversions and valley cloud will be dominating the area, with warm alpine temp's and cool, cloudy valleys.
Snowpack Summary
20cm of storm snow is currently being redistributed by strong N winds. These storm slabs overlie a variety of surfaces, including suncrust on steep S-SW aspects, with 2-3mm surface hoar on most other aspects. Below this, windslabs appear to be bonding and the snowpack as a whole is strengthening. A weak basal layer exists on alpine N/NE aspects.
Avalanche Summary
A few isolated size 2 slabs have been observed from steep S-facing alpine terrain this morning. Several large (size 3) avalanches were observed in the Swiss Peak group over the weekend, so the weak basal layer on N/NE alpine aspects is not bonding well at the moment.
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.
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.