Avalanche Forecast
Regions: Olympics.
The avalanche danger should be greatest early Saturday following the storm Friday. Watch for wind loaded terrain and avoid steep slopes suspected of wind deposits. Conditions should improve as the snow pack slowly stabilizes through Saturday afternoon.
Detailed Forecast
Continued periods of light to moderate snow at cool temperatures, Friday night, along with strong winds.
This weather should build wind slabs on lee slopes near and above treeline. Watch for firmer wind transported snow, mainly on the lee slopes facing N to SE, below ridges.Â
Heavier precipitation rates Friday night should increase the storm slab likelihood by early Saturday.Â
Showers should end quickly early Saturday with partial clearing and diminishing winds. Cooler temperatures should continue Saturday.Â
Watch for greater depths of storm snow and avoid wind loaded terrain and steep rollover features.Â
Storm snow problems should improve through the day Saturday as upper snow layers settle and stabilize.
Snowpack Discussion
Weather and Snowpack
Dry weather with the warmest temperatures of the winter occurred February 7-10th with mild temperatures and high freezing levels.Â
Rain and mild temperatures predominated Sunday and Monday with 1.5 inches of rain before a brief cooling trend brought a few inches of snow by Tuesday morning. Mild temperatures and windy conditions were seen on Wednesday.
Storm snow of 4-6 inches accumulated as of Friday afternoon 2/19 at cooler temperatures with strong winds. Â
Recent Observations
Professional NWAC observer, Matt Schonwald was at Hurricane Ridge on Friday, Feb 19th. Recent storm snow deposits of about 4-6 inches had accumulated in wind sheltered locations. Very strong southerly winds where building shallow wind slabs on lee slopes near tree line below ridges and also building small cornices. No distinct layers were noted in the shallow new storm snow that was generally well bonded to the draining old wet snowpack.Â
The main concern would be new snow instabilities, specifically new wind slab deposits, near and above treeline. Secondarily, small storm slabs, however, as of Friday afternoon, the storm deposits were insufficient to cause a significant danger increase.
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.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 1
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: All elevations.
Likelihood: Possible
Expected Size: 1 - 1