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Avalanche Forecast

Archived

Jan 26th, 2018–Jan 27th, 2018

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.

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. 

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. 

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. 

Problems

Wind Slabs

Wind Slab avalanches are the 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.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). 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.

Loose Wet

Loose Wet avalanches are the 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. 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.