Avalanche Forecast
Regions: Olympics.
Dangerous avalanche conditions are expected early Friday, mainly near and above treeline. Best to limit objectives by avoiding steep and wind loaded slopes, watching for sensitive storm layers. Recent and newly wind loaded slopes in the near and above treeline zone should be found on a variety of aspects Friday.
Detailed Forecast
A frontal system overnight Thursday should give way to showers and cooling Friday. Â Â
Avalanche problems Friday should be associated with new storm and wind slab layers. New and recent snow will be deposited on lee NW through E aspects. Most avalanches should stay within the new storm snow, but a few may step down to older storm layers or crusts in isolated locations. Â
In areas below treeline, the warming and rain may have caused natural avalanches on some steep slopes. In addition cooling should begin to form a new crust layer below the elevation that experienced rain or wet heavy snow, likely about 5500 feet. This should limit any avalanches to mainly shallow new snow. Â
However, near and above treeline, increasing snowfall and winds are expected overnight Thursday and early Friday. This should cause sensitive storm layers. Therefore, best to avoid steeper slopes and those showing signs of recent wind loading. Â
Terrain anchors are still causing significant anchoring at the lowest elevations. Use caution near creeks which are still open in some areas.
Snowpack Discussion
An atmospheric river around Dec 9th pushed heavy rain above treeline in the Olympics. This caused consolidation and stabilizing of the older part of the Olympics snowpack. An active and cool weather pattern over the last week has produced about 2 to 3 plus feet of new snowfall near Hurricane Ridge that now sits over the 12/9 rain crust.
Last Sunday an NPS Ranger at Hurricane Ridge reported a storm slab release below the Sunrise Ridge likely on an east facing slope near Hurricane. The slide was likely triggered, but this was not confirmed.  The avalanche crown was estimated at 2-3 feet and released about 150 wide and ran about 100 feet vertical - big enough to get into serious trouble.
Early this week, cool weather with light new snowfall occurred. A strong frontal system is producing moderate to heavy rain or snowfall at rising freezing levels Thursday.  The heavy wet snow or rain should cause a significant increase in danger as the weak underlying snow becomes heavily loaded.
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: 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: Likely
Expected Size: 1 - 1