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Archived

Avalanche Forecast

Feb 19th, 2015–Feb 20th, 2015
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
1: Low
The avalanche danger rating in the alpine will be low
Treeline
1: Low
The avalanche danger rating at treeline will be low
Below Treeline
1: Low
The avalanche danger rating below treeline will be low

Regions: Cascades - South West.

A low avalanche danger is expected in most areas on Friday. But the near and above treeline for Crystal Mountain to Mt Rainier has been updated Friday morning.

Detailed Forecast

A weak short wave in a weak west flow moved over the Northwest Thursday and Thursday night. This caused light showers west of the crest with lower snow levels. Northwest flow should maintain some light showers mainly west of the crest on Friday.

The light amounts of rain or snow Thursday to Friday should not significantly change snow conditions in most areas west of the crest.

Update: The expected convergence Thursday night gave some snowfall in a slightly unexpected area with about 3-5 inches of snowfall from about Crystal Mountain to Mt Rainier with light to moderate west winds. So this area has been updated for unlikely small storm slab in the near and above treeline.

As a result of the overall low snowpack, especially below treeline, watch for terrain hazards such as open creeks, partially covered rocks and vegetation.

Snowpack Discussion

A benign weather pattern with mild temperatures has been seen in the Olympics and Cascades for about the past 10 days.

There has been a lot of consolidation and melting and freezing of surface layers of the snow pack in all areas including west of the crest. There were some reports of small loose wet avalanches on steep solar slopes a few days ago. But there have been no reports of avalanches more recently mainly just some reports of spring-like corn skiing at times.

Pro-observer Dallas Glass was at Paradise on Wednesday and reported some shallow softening on solar slopes, MF clusters throughout the snowpack and no instability.

Reports this morning west of the crest indicate strong thick surface crusts. Overall the mid and lower snowpack west of the crest should consist of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter.

 

Avalanche Problems

Storm Slabs

Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. 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.

 

You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.

 

Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood: Unlikely

Expected Size: 1 - 1