Avalanche Forecast
Issued: Dec 27th, 2013 10:00AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs.
NWAC,
Northwest Avalanche Center
Summary
Detailed Forecast
Decreasing winds, decreasing clouds and mostly sunny weather should be seen Saturday. Warmer temperatures should be seen by Saturday afternoon.
The main concern should be any small shallow new wind slab built on lee slopes in the alpine and perhaps in the near treeline by the front on Friday.
Minor wet loose avalanches might also be possible by Saturday afternoon on solar aspects.
Shallow amounts of stable snow that generally bond well to previous snow should be seen on most other slopes but again only in the alpine or near treeline.
Snowpack Discussion
The last significant snow at Hurricane occurred in early December. Either strong high pressure or systems with high freezing levels have limited the snow accumulations in the Olympics and specifically at Hurricane Ridge where the total snowdepth remains a meager 13 inches. The NWAC weather station at Hurricane has recorded less than 2 inches of water through December.
The overall shallow snowpack has been limiting the avalanche danger, especially near tree line and below tree line where significant terrain and vegetative anchors remain. Field observations at Klahhane Ridge Sunday indicated the lack of snow on most slopes. On north facing slopes below the ridge there was evidence of old wind slab which was not reactive in tests. Rain to high elevations and lack of recent snow is maintaining mostly stable conditions with surface crusts or shallow wind drifts over crust layers.
A front is crossing the Northwest on Friday. This will cause southwest winds to shift to the northwest with rain changing to a little snow at the higher elevations in the Olympics with cooling temperatures.
View looking east along Klahhane Ridge, Olympics 12-22-2013, K. Reid
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.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Dec 28th, 2013 10:00AM
