Avalanche Forecast
Regions: Olympics.
As this storm cycle continues, dangerous avalanche conditions will persist in the Olympics. This is a time for very conservative travel in the mountains. Avoid bigger avalanche terrain where large and destructive avalanches can occur. Give safe margins near and below growing cornices. Numerous hazards will challenge your ability to travel safely in the mountains Saturday.
Detailed Forecast
A slight warming trend, gusty winds and showery weather will help maintain dangerous avalanche conditions in the Olympic Mountains.
Winds slabs formed near and above treeline have grown large during this storm cycle. As sensitive wind layers become buried deeper, they will become more difficult to trigger but can still result in a large and destructive avalanche. Large and sensitive cornices found along ridges would make for the perfect trigger to unleash a deeper wind slab avalanche.Â
Relatively warmer temperatures, gusty winds and occasional showers will make triggering storm slabs easier. As snow showers change to rain showers at lower elevations, expect loose dry avalanches to transition to loose wet on steeper slopes. Be aware of the consequences of a loose avalanche above terrain traps.Â
With all the new snow, this is a time to stick to safer terrain. The potential for large and destructive avalanches remain, so avoid travel on or below slopes connected to large avalanche paths until we exit this storm cycle. Give safe margins near and below growing cornices. There's plenty of good snow out there, so maintain a conservative approach to terrain selection.
Snow conditions changed significantly during this extended storm cycle. Tree-well and snow immersion hazards are very dangerous, so keep communication with your partner at all times.
Snowpack Discussion
A very active weather pattern continues to impact the Olympics. At Hurricane Ridge 4 feet or more of settled storm snow sits atop the 1/17 crust layer.
Fluctuations in air temperature and precipitation intensity throughout the storm cycle created several weaklayers and a thin rain crust within the storm snow. Depth and sensitivity of these layers depends upon location.
Moderate winds transported snow near and above treeline forming wind slabs on a variety of aspects.
Observations
On Friday pro-observer Matt Schonwald reported on the tremendous change in the snowpack since this storm cycle began. A steady dose of southerly winds plus near continuous snowfall over the last week and a half has sculpted the landscape near and above treeline with large and very sensitive cornices, deep wind rolls and huge snowdepth variations in wind-affected terrain. Shallow wind slabs were easy to trigger on lee slopes near treeline. Snowdepth on a south aspect at 5000' measured 120 cm vs. 370 cm at the same elevation on a northerly lee aspect. Loose dry avalanches presented a real danger where terrain traps were present.Â
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: All aspects.
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
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.
Elevations: Below Treeline.
Likelihood: Likely
Expected Size: 1 - 1