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Avalanche Forecast

Archived

Dec 2nd, 2015–Dec 3rd, 2015

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Northwest Coastal.

The next storm is forecast to move into the region tonight. New snow and wind will result in HIGH avalanche danger.

Confidence

Poor - Timing, track, or intensity of incoming weather system is uncertain

Weather Forecast

The next pulse in a series of Pacific storms is expected to push into the region this evening and continue to produce moderate precipitation during the day on Thursday. Friday should be a bit of a break between storms, but still overcast with convective periods producing flurries. Cooler air is forecast to start moving down from the north on Friday bringing the freezing level down to valley bottoms. At this time the Saturday system does not look like it will produce much precipitation in the north, stay tuned as we watch the models evolve.

Avalanche Summary

No new avalanches reported. I suspect that new storm slabs are developing and may be easily triggered by light additional loads.

Snowpack Summary

The snowpack is highly variable across different aspects and elevations. So far, we only have limited information from the field. Initial reports suggest that there is around 150 cm at 2000 m. Recent winds have scoured exposed slopes, and left variable wind slabs and crusts. In some places, a crust/facet interface or surface hoar can be found in the upper snowpack. At high elevations, a crust which formed early season may exist near the base of the snowpack. The new storm snow may not bond well to the mix of old surfaces left behind after the recent high pressure. Buried surface hoar may be found below the new storm snow at lower elevations, or in areas where the recent temperature inversion was not strong enough to melt it.

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.