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Avalanche Forecast

Archived

Feb 16th, 2016–Feb 17th, 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

Mt Hood.

A mixed bag of conditions seems possible on Wednesday 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 Wednesday.

Detailed Forecast

An occluded front should rotate out of a low pressure system over the Northwest coastal waters late Wednesday. This should cause light rain or snow to spread to the Olympics and Cascades Wednesday afternoon. Further increasing rain or snow should be seen Wednesday evening especially on the volcanoes. Temperatures will remain mild on Wednesday.

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

This forecast will be conservative and list wind slab as possible in the above tree line on Wednesday. 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.

You should continue to watch for loose wet avalanche conditions in the near and below treeline on Wednesday. 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.

Wet slab avalanches won't be listed as a problem but quickly change your plans if you see evidence of wet slab avalanches. You can check for significant liquid water in layers in snow pits.

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

 

Snowpack Discussion

Weather and Snowpack

Dry weather with the warmest temperatures of the winter occurred February 7-10th with temperatures climbing into the 50's and even the 60's.

A pair of warm fronts brought about 9-15 inches of new snow to Mt Hood about Thursday to Saturday.

Rain and and mild temperatures predominated along the west slopes Sunday and Monday. NWAC sites at Mt Hood had rain in the 2.5 inch range for the 2 days ending this morning.

Bonds should be good in the upper snowpack along the west slopes. The mid and lower snowpack should be mostly consolidated and stable.

Recent Observations

The Mt Hood Meadows pro-patrol reported a widespread natural cycle of loose wet avalanches on Sunday morning.

On Monday the Meadows pro-patrol reported no avalanches with consolidated snow and surface runnels up to 7000 feet.

Today the Meadows pro-patrol reported numerous large 1 foot wet slab avalanches in White River Canyon up to 100 yards wide at 5-6000 feet below a ridge with cornices. A small loose wet avalanche was also reported in Heather Canyon.

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.