Avalanche Forecast
Regions: Olympics.
A storm Sunday night is expected to cause high danger near and above treeline to last into Monday.
Detailed Forecast
Strong winds and snow showers will gradually decrease on Monday with cool temperatures.
New potentially deep storm slab will be likely on all sheltered aspects. New potentially deep wind slab will be likely on lee slopes. Natural or triggered avalanches should be likely especially near or above treeline on Monday. Avalanches may step down or reach the crust from Wednesday. Travel in avalanche terrain near and above treeline is not recommended on Monday unless you are sure the danger is less than expected.
Snowpack Discussion
Recent Northwest Weather
An extended dry mild period was seen the latter half of January. The was followed by very cold weather which produced low density snowfall and near surface faceted snow in early February. Now for the past 6 days the Northwest is getting pummeled by daily frontal systems producing periods of strong winds, periods of warmer higher density snowfall and rain during periods of generally warmer temperatures.
Water equivalents in the Cascades near and west the past 6 days are in the 3-7 inch range with snowfall in the 2-4 foot range. Less data is available for the Olympics but should be similar. Note this means there has to have been some rain or generally heavy wet snow the past 6 days.
Hurricane Ridge
At Hurricane this weather has been building deep new snow and a rain crust from Wednesday over colder lower density snow from early February in turn over surface hoar frost and a crust from late January.
A park ranger and NWAC observer Tyler Reid at Hurricane Ridge Friday reported one ski triggered D2 avalanche on a northeast slope at 5200 feet on Friday.
A snow profile at Hurricane Ridge over the weekend on a southeast slope had about 20 cm of F DF storm snow, over a 3 cm MF rain crust from last Wednesday, over 22 cm of F+ RG recent snow over 4F snow over crusts from January. Snow pit tests by Tyler on Saturday gave moderate to hard, SP results and potential to propagate on the MF crust.
Tyler gave us a video of the tests https://www.youtube.com/watch?v=XBqeIeqkGao
Limited snow at the lowest elevations will limit the avalanche danger there. The mid and base pack should still consist of mostly stable crusts and melt form layers from periods of warm weather earlier this winter.
The next very strong cold front will cross the Olympics and Cascades Sunday night. This will produce stormy weather with very strong winds, slight warming and then cooling, and heavy snowfall. An avalanche cycle is likely Sunday night.
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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: All elevations.
Likelihood: Likely
Expected Size: 1 - 1
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