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Avalanche Forecast

Archived

Feb 4th, 2017–Feb 5th, 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.

Despite a cooling trend, recently formed storm slabs may still be sensitive Sunday. Colder temperatures will help preserve wind slab instabilities near and above treeline. Enjoy the new snow but choose conservative terrain and allow storm related instabilities time to heal.  

Detailed Forecast

More snow is on the way Saturday night with a cooling trend and generally light snow showers forecast for Sunday. SW  winds should decrease during the day, becoming E or NE by the afternoon.  

Despite a cooling trend, recently formed storm slabs may still be sensitive Sunday. While storm slabs are most likely to release within the most recent storm layers, various crusts throughout the area are capable of providing bed surfaces for larger avalanches in isolated terrain. 

Colder temperatures will help preserve wind slab instabilities near and above treeline. We've highlighted more traditional lee easterly aspects on the elevation/aspect diagram, but be aware of cross-loaded slopes and that easterly winds earlier in the week loaded westerly aspects. Feel for firmer wind transported snow as you climb higher in the terrain.  E-NE winds should start to move snow to more westerly aspects Sunday night. 

Enjoy the new snow but choose conservative terrain and allow storm related instabilities time to heal.  

 

Snowpack Discussion

Weather and Snowpack

Strong NE-E winds were seen this past Wednesday and Thursday with very cold temperatures. 

A storm cycle began Friday with generally 1-2 feet of snow accumulating at Hurricane Ridge area through 5 pm Saturday. Steady and moderate snow levels through the storm cycle began to lower Saturday afternoon. 

Recent Observations

NWAC pro-observer Matt Schonwald was at Hurricane on Friday (before most of storm snow arrived) and found scoured slopes or shallow new snow on E slopes and shallow building wind slab on SW slopes. He found no significant signs of instability, ski tracks still visible from last week and lots of surface roughness to fill in on lee slopes.

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.