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Avalanche Forecast

Archived

Dec 9th, 2015–Dec 10th, 2015

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

Olympics.

Evaluate snow and terrain carefully Thursday. Change your plans if you find yourself in unexpectedly prolonged stormy weather.

Detailed Forecast

Olympics Forecast

An occluded front should move south to north over the Northwest Wednesday night and Thursday. South to southeast alpine winds Thursday morning should generally shift to southwest Thursday by afternoon. Look for mostly moderate amounts of snow by later Thursday.

Watch for possible new wind slab on lee slopes and new storm slab in calmer less exposed areas above and near treeline. The mostly moderate amounts of snow and the cooling should somewhat limit the extent of new wind and storm slab. Remember that the avalanche danger will be greater if you encounter stronger winds and heavier snowfall. Evaluate snow and terrain carefully Thursday. Change your plans if you find yourself in unexpectedly prolonged stormy weather.

Little snow below tree line should greatly limit the avalanche danger there.

Snowpack Discussion

Olympics Weather:

It looks like little snow was seen the first 7 days or so of December at Hurricane. Then an atmospheric river arrived the past couple days (Main Fork of the Pineapple Express) and this should have caused heavy rain in the Olympics.

But snowfall has resumed on Wednesday with a cooling trend. Good news!

Olympics Snowpack and Reports:

Given the warm, wet weather over the Olympics the past few days, it is very likely that the upper snowpack has become stable, consolidated and well drained. We have not specific snowpack observations from Hurricane Ridge so far this season.

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.