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Archived

Avalanche Forecast

Feb 8th, 2016–Feb 9th, 2016
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Olympics.

Another warm and sunny day with freezing levels above 12,000 feet Tuesday will keep the avalanche danger focused on loose wet avalanches. Steeper solar slopes should be the most likely places for natural or skier triggered loose wet avalanches. Solar slopes involve more than just due south aspects as we head further into February, including east in the morning and southwest to west facing by afternoon. 

Detailed Forecast

Another warm and sunny day with light winds is expected again Tuesday. Temperatures pushed into the low 60's Monday afternoon and it may be a few degrees cooler Tuesday. The avalanche danger will again focus on loose wet avalanches. Steeper solar slopes should be the most likely places for natural or skier triggered loose wet avalanches. Solar slopes involve more than just due south aspects as we head further into February.  

Be aware of loose wet avalanche potential above terrain traps (like above cliffs or near gullies), where even small wet avalanches can become powerful and have unintended consequences.  

Lingering wind slab on lee slopes near and above treeline should be stubborn to trigger, but still possible in isolated locations on Tuesday. 

Watch for recent cornices along ridges which may become sensitive to trigger or release naturally during the warm weather. 

Snowpack Discussion

The warmest weather of the season is upon us Monday, Feb. 8th. Temperatures at Hurricane Ridge have ranged from the mid 40's to the low 60's Monday with snowpack settlement of about 6 inches since Sunday morning.

The very mild temperatures, sunshine and snowpack settlement have likely settled storm layers of wind slab and buried surface hoar reported over the weekend from storms late last week and the fast moving storm with strong S_SW winds Friday night. The storm snow amounts from late last week through Saturday amounted to about 14-16 inches.  

On Saturday, an observation on the NWAC page submitted by a professional guide identified a sensitive buried surface hoar layer on a north aspect near Hurricane Ridge.  Shooting cracks were observed, but no avalanche activity was observed on this layer.  

Also on Saturday, a NPS ranger reported a snowboarder triggered a wind slab avalanche on an NE aspect just outside of the ski area. The snowboarder was not caught, but the soft wind slab avalanche had a 1-2 ft crown. 

Abundant wet surface snow and sensitive cornices are the current key snowpack features. 

Avalanche Problems

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: South East, South, South West, West.

Elevations: All elevations.

Likelihood: Likely

Expected Size: 1 - 1

Cornices

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind lips of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

 

Cornices can never be trusted and avoiding them is necessary for safe backcountry travel. Stay well back from ridgeline areas with cornices. They often overhang the ridge edge can be triggered remotely. Avoid areas underneath cornices. Even small Cornice Fall can trigger a larger avalanche and large Cornice Fall can easily crush a human. Periods of significant temperature warm-up are times to be particularly aware.

 

A corniced ridgeline. A large cornice has formed at the top of the ridge. A smaller cornice has formed to the left of the trees from crossloading.

Cornices are easy to identify and are confined to lee and cross-loaded ridges, sub-ridges, and sharp convexities. They are easiest to trigger during periods of rapid growth (new snow and wind), rapid warming, and during rain-on-snow events. Cornices often catch people by surprise when they break farther back onto flatter areas than expected.

Aspects: North, North East, East, South East, North West.

Elevations: Alpine, Treeline.

Likelihood: Possible

Expected Size: 1 - 1