Regions
Northwest Coastal.
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Confidence
Fair - Timing or intensity of solar radiation is uncertain
Weather Forecast
The ridge of high pressure rebuilds on Friday resulting in dry and sunny conditions for the next three days. On Friday, freezing levels should reach around 800m and alpine winds should be moderate-to-strong from the NE. On Saturday, the lower freezing level may reach around 1000m. However, an inversion may form and there is the potential for a layer of warm air to sit at alpine elevations. Alpine winds are forecast to remain moderate-to-strong. Conditions should be much the same on Sunday.
Avalanche Summary
On Tuesday, an explosive-triggered size 1 wind slab avalanche was reported. On Monday, numerous wet releases up to Size 2 were reported from steep sun-exposed slopes. Isolated cornice failures and ice falls were reported during the last sunny period. Last week several full-depth avalanches up to Size 3 were observed on all but North aspects. As we get increased sun and warming heading into the weekend, these types of avalanches could once again become a problem.
Snowpack Summary
A dusting of new snow may have buried the previously variable snow surface which may have included wind-pressed surfaces or old wind slabs, a sun crust or old rain crust, surface hoar, and/or surface facets. A layer of surface hoar buried in the upper snowpack has been reported in some areas and is worth investigating before committing to any big alpine terrain. At the base of the snowpack, weak facets may be persisting.
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.