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Avalanche Forecast

Archived

Nov 30th, 2017–Dec 1st, 2017

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

Regions

Olympics.

Wind slab is the most likely avalanche problem to encounter on Friday in the Hurricane Ridge area. Approach cautiously and watch for firmer wind-transported snow on lee slopes near ridges. Early season terrain hazards still exist, such as poorly covered rocks, vegetation and creeks, particularly at lower elevations.

Detailed Forecast

On Friday, a frontal system should stall over the Olympics and north Cascades before finally sagging south in the late afternoon and evening. Alpine winds generally out of the S-SW will increase late Thursday night and stay elevated through Friday. New and generally shallow storm snow instabilities may develop in the Olympic zone on Friday. However, fresh wind slab may build at higher elevations in all zones during the day. 

Wind slab is the most likely avalanche problem to encounter on Friday in the Hurricane Ridge area. Watch for firmer wind-transported snow on lee slopes near ridges, generally west through southeast aspects, but expect wind deposited snow on a variety of aspects in areas of more complex terrain.

Early season terrain hazards still exist, such as poorly covered rocks, vegetation and creeks, particularly at lower elevations.

Snowpack Discussion

Avalanche and Weather Summary

The great start to the 2017/18 PNW Winter lasted through mid November. Warm, wet weather before Thanksgiving caused wet snow and glide avalanches and snowpack consolidation with total snow depths decreasing by 50% or more from their mid-November peak depths. The old wet snow continues to slowly refreeze and from a crust of variable strength.

A series of fast moving frontal systems have brought several inches of snow to the Olympics and the west slopes of the Cascades this week. Mt. Baker has received the most snow since Monday, about 2 feet. Over at Hurricane Ridge, temperatures have hovered near the freezing mark likely leading to rapid stabilization of the new snow that fell over the course of the week.

Observations

No recent observations from Hurricane Ridge. See Cascade zones for their local observations. 

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.

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.