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Avalanche Forecast

Archived

Feb 17th, 2016–Feb 18th, 2016

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

Regions

Olympics.

A cooling trend Wednesday night and Thursday should limit the loose wet problem to below treeline. Shallow new wind slab may build on lee slopes near and above treeline Thursday. 

Detailed Forecast

An occluded front pushing through Wednesday night should be followed by light showers on Thursday and a cooling trend. 

Shallow wind slab may build on lee slopes near and above treeline Thursday. Watch for new firmer wind transported snow mainly on lee N to SE slopes near ridges. 

You should continue to watch for loose wet avalanche conditions below treeline Thursday especially on steeper slopes. Watch for wet surface snow deeper than a few inches that usually precede loose wet avalanches or other triggered or natural loose wet avalanches. 

Snowpack Discussion

Weather and Snowpack

Dry weather with the warmest temperatures of the winter occurred February 7-10th with mild temperatures and high freezing levels. 

A pair of warm fronts brought about 6 inches of new snow to Hurricane about Thursday to Saturday.

Rain and mild temperatures predominated Sunday and Monday with 1.5 inches of rain before a brief cooling trend brought a few inches of snow by Tuesday morning. Mild temperatures and windy conditions were seen on Wednesday. 

Recent Observations

Professional NWAC observer Matt Schonwald was at Hurricane Ridge on Friday, Feb 12th. Recent warmth and persistent winds had generally created a dense and homogeneous snowpack without layers of concern. In the Hurricane Ridge area the snowdepth falls off rapidly below 4400 feet. Bare patches and/or thin snow cover are widespread along ridges and on south to west aspects. Matt and an NPS ranger did observe 2 glide avalanches that likely occurred the night of Feb 11th. The larger one, size D2.5, released in the 20th of June path down to a smooth shale bed. However, except in isolated terrain features, glide avalanches should not be a widespread concern in the Hurricane Ridge area. 

No direct snowpack or avalanche observations have been received mid-week, but the snowpack is likely still homogenous with wet grains dominating the upper snowpack. 

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.

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.