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Avalanche Forecast

Archived

Dec 31st, 2018–Jan 1st, 2019

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Stevens Pass.

The bottom line: Happy new year! If traveling to upper elevations use caution where deep wind drifts exist over open slopes. In adjacent zones, people have been able to trigger avalanches on a layer of buried surface hoar near and above treeline. This should give us pause, and reason to avoid these types of features. 

Snow and Avalanche Discussion

The storm that ended on the 30th past storm brought about 17” inches of new snow with 3.3” of water equivalent to Stevens Pass. It rained up to at least 5200ft during the storm, then a cold front with strong winds blew through as the snow accumulated. We are left with fresh, cold snow over a refreezing wet snow crust, and some deep wind drifts. On the 30th, ski area snow safety teams were able to trigger wind slabs big enough to injure, bury, or kill a person with control work. Numerous human triggered avalanches have been reported in adjacent zones. These appear to be failing on a layer of buried surface hoar from Christmas. In the East Central Zone, observers remotely triggered slides 18" deep on Northeast to Southeast aspects above 6,000ft. One of these was triggered from 200ft away.

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.