Avalanche Forecast
Regions: Olympics.
The avalanche danger will increase sharply Sunday with human triggered slides becoming likely. Choose a conservative travel plan and make sure your plan allows for a safe exit if conditions deteriorate quicker than expected.
Detailed Forecast
Light snowfall Saturday night and Sunday morning will increase in intensity Sunday afternoon along with increasing winds. A warming trend should lead to inverted storm snow by mid-day Sunday. Snow should change to rain at below and near treeline by Sunday afternoon.Â
All of this will lead to quickly increasing avalanche danger Sunday. Expect human triggered avalanches to be likely as the day wears on.Â
Natural loose wet avalanches will become very likely on steeper slopes with the change to rain.Â
Storm slab avalanches releasing within the storm snow may step down to a variety of surfaces including recently formed crusts or the aforementioned graupel layer. Storm slabs will be more likely to trigger on wind loaded lee aspects.Â
More significant warming and precipitation is expected Sunday night and a natural avalanche cycle is expected. Â
Snowpack Discussion
A storm system hit the Northwest last weekend with strong west to northwest winds. The NWAC site at Hurricane picked up about 12 inches of storm snow with a good cooling trend. Strong northeast winds hit at the tail end of the storm Monday and Tuesday. This transported snow and formed some local wind slab on exposed slopes and near ridges but in most areas this layer bonded well and lacked underlying weak layers.
An upper ridge over the coastal waters tilted inland Wednesday and Thursday producing sunny weather and warm temperatures at higher elevations. NWAC observer Tyler Reid was at Hurricane Ridge on Wednesday and reported widespread small wet loose avalanches.
On Saturday, NWAC pro-observer Katy Reid confirmed a 3 cm graupel layer at 10 cm below the surface on E-NE aspects near and below treeline. This layer could become reactive during the upcoming storm. One of our biggest concerns heading into the upcoming storm will be the new storm snow's ability to bond to a variety of snow surfaces; near surface facets, wind board, melt-freeze crusts, etc. Â
Graupel layer at Hurricane on Wednesday by Tyler Reid.
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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
Loose Wet
Release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Move to colder, shadier slopes once the snow surface turns slushly. Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches.
Several loose wet avalanches, and lots of pinwheels and roller balls.
Loose wet avalanches occur where water is running through the snowpack, and release at or below the trigger point. Avoid terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Very Likely
Expected Size: 1 - 1