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Avalanche Forecast

Archived

Apr 1st, 2015–Apr 2nd, 2015

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

Regions

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Sunshine and daytime warming may melt and weaken the recent storm snow, especially on solar aspects. Also, watch for weakening cornices and possible wind slabs near ridges. 

Detailed Forecast

Partly cloudy skies with sunny periods, cool temperatures and light winds are expected Thursday. 

In areas that have enough snow cover to provide a bed surface, shallow, loose wet avalanches involving the recent storm snow will be possible with daytime warming. Also, lee easterly aspects may harbor shallow wind slab at higher elevations.  

Cornices won't be listed as an avalanche problem, but be aware of new cornice growth along ridgelines.

Snowpack problems west of the crest should remain in the upper or surface layers. The mid and lower snowpack west of the crest consists of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this season. Many areas at the lowest elevations do not have enough snow to cause an avalanche danger.

Snowpack Discussion

Winter-like conditions last week was followed by reports of natural and skier triggered, loose avalanches on Tuesday, Mar 24th along the west slopes. This was followed by a warm front and heavy rain last Wednesday through Thursday morning. This caused an avalanche cycle west of the crest with many large natural avalanches observed in the Mt Rainier area above treeline.

A frontal system brought 2-3 inches of snow at higher NWAC stations west of the crest Friday night. The new snow was reported to have bonded well to the previously moist surface. Mt. Baker picked up another inch of water Sunday and Sunday night with snow levels 5-6000 ft while other locations experienced fair weather. Fair and mild weather Monday, caused more snowpack settlement. 

Snow levels fell quickly after a front moved through early Tuesday morning, followed by showers overnight and Wednesday. This most recent snow has amounted to 4-6 inches in most areas along the west slopes with the exceptions of the Snoqualmie Pass area where 15 inches accumulated at pass level and 2 feet at the 5000 ft level. Paradise on Mt Rainier received about 10 inches as of Wednesday.   

A bit surprising has been the reports from ski area patrollers at Alpental and Crystal Mountain Wednesday, that the new snow quickly settled with little to no avalanche activity from control work, including ski cutting. There was evidence at Alpental that a natural cycle occurred before daylight Wednesday, likely during some heavy loading in the early morning hours.  A testament to how quickly new snow is able to settle and stabilize as we move into April. By Wednesday afternoon, the snow had settled 6 inches at the Snoqualmie Pass level from the early morning depths.

Problems

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.

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.