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Avalanche Forecast

Archived

Feb 15th, 2016–Feb 16th, 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 unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Olympics.

A mixed bag of conditions seems possible on Tuesday with winter like snow conditions possible in the above treeline and wet snow conditions in the near and below treeline. Several types of avalanche problems will need to be watched for on Tuesday.

Detailed Forecast

A weak cold front will cause rain or snow to shift from north to south over the Olympics and Cascades tonight to Tuesday morning with a slight drop in snow levels. Up to a few inches of snow should be seen in the above treeline with some more rain in the near and below tree line.

Another weak warm front should lift south to north over the Northwest Tuesday afternoon and night and cause light rain or snow with another slight rise in snow levels.

A mixed bag of conditions seems possible on Tuesday with winter like snow conditions possible in the above treeline and wet snow persisting in the near and below treeline.

This forecast will be conservative and list new wind slab as possible in the above tree line in the Olympics on Tuesday. Watch for new firmer wind transported snow mainly on lee N to SE slopes near ridges. You will need to be able to assess this problem for yourself if you travel above treeline on Tuesday.

You should continue to watch for loose wet avalanche conditions in the near and below treeline on Tuesday. Watch for wet surface snow deeper than a few inches that usually precede loose wet avalanches or other triggered or natural loose wet avalanches. Steep slopes near and below treeline are probably still best avoided on Tuesday.

Glide avalanches won't be listed as a problem but avoid areas below steep rocks still holding snow since these slopes can release at unpredictable times.

Storm slab also won't be listed as a problem but watch for this type of layer in area if you find yourself in an area that rapidly accumulated snow on Monday night. A cooling trend, near freezing temperatures and good bonding should limit the possibility of this type of layer. You can test for it with quick hand shear or shovel tilt tests.

Snowpack Discussion

Weather and Snowpack

Dry weather with the warmest temperatures of the winter occurred last Sunday to Wednesday with temperatures climbing into the 50's and even the 60's.

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

Rain and and mild temperatures predominated Sunday and today. Hurricane will have about 1.5 inches of rain for the 2 days ending Tuesday morning.

Recent Observations

Professional NWAC observer, Matt Schonwald was at Hurricane Ridge on Friday. 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 or thin snow cover is widespread along ridges and on south to west aspects. Matt and an NPS ranger did observe 2 glide avalanches that likely occurred Thursday night. The larger one, size D2, released in the 20th of June path down to a gravel bed. However, except in isolated terrain features, glide avalanches should not be a widespread concern in the Hurricane Ridge area. 

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.