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Archived

Avalanche Forecast

Jan 30th, 2017–Jan 31st, 2017
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
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

Regions: Olympics.

Wind slab formed over the weekend and found mainly on northwest to southeast slopes near and above treeline continues to be the most likely avalanche problem in the Olympics. 

Detailed Forecast

A clearing trend is likely for the Olympics Tuesday except along the north slopes where light upslope snow showers are possible with breezy E-NE winds developing late in the afternoon. 

Wind slab formed over the weekend and found mainly on northwest to southeast slopes near and above treeline continues to be the most likely avalanche problem in the Olympics.  

Snowpack Discussion

Weather and Snowpack

An atmospheric river arrived over the Northwest Tuesday 1/17 with heavy rain seen up to at least 6000 feet in the Hurricane Ridge area.

A storm cycle from Thursday 1/19 through Sunday 1/22 deposited about 2 feet of snow at Hurricane Ridge.

A large upper ridge and warm air mass built over the Northwest Thursday to Saturday. Temperatures warmed into the 40s at Hurricane with south winds in the 20 mph range on Saturday.

A weak front crossed the PNW Sunday afternoon and night, depositing 1 inch of new snow at Hurricane Ridge through Monday morning after starting as light rain Sunday afternoon. A slight cooling trend under mostly cloudy skies followed on Monday.  

Recent Observations

A skier triggered and was carried by a wind slab avalanche on the back side of Maggies on Saturday and a report with a well done video is available on the NWAC Observations page.

Another report for Saturday for the Obstruction Point road area via the NWAC Observations page indicated windy and warm conditions, with pinwheels, roller balls and surface crusts on W-SW slopes.

Avalanche Problems

Wind Slabs

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.

 

Wind Slabs form in specific areas, and are confined to lee and cross-loaded terrain features. They can be avoided by sticking to sheltered or wind-scoured areas..

 

Wind Slab avalanche. Winds blew from left to right. The area above the ridge has been scoured, and the snow drifted into a wind slab on the slope below.

 

Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.

Aspects: North, North East, East, South East, North West.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 1