Avalanche Forecast

Archived

Feb 10th, 2015–Feb 11th, 2015

Alpine

Natural and human triggered avalanches likely.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches possible, human triggered probable.

Regions

Mt Hood.

The primary concern Wednesday at Mt Hood should be loose wet snow avalanches.

Detailed Forecast

Fair weather should be seen on Wednesday with some high clouds especially over the Olympics and north Cascades. Quite a rise in freezing levels should be seen Wednesday especially at Mt Hood so that means significantly warmer temperatures.

The main problem on Wednesday at Mt Hood should be loose wet avalanches. Watch for natural or triggered rollerballs that would initially be see on steep solar slopes but that could spread to other slopes. All of the recent snow should be available for entrainment so that is a lot of snow at Mt Hood in the above treeline. Don't underestimate the power of slow moving loose wet snow avalanches which could take you some where you don't want to go such as into gullies or other terrain traps and then sets up like concrete. These conditions should extend to some extent down into the near treeline and the upper part of the below treeline.

Lingering wind slab will be listed as a problem for one more day at Mt Hood above tree line. Watch for firmer wind transported snow on previous lee slopes mainly on N-SE slopes near ridges.

As a result of the overall low snowpack, especially in the lower part of the below tree line, watch for terrain hazards such as open creeks, partially covered rocks and vegetation.

Snowpack Discussion

A series of fronts in an atmospheric river crossed the Northwest the past few days. NWAC sites at Mt Hood had about 2 inches of WE mostly as rain. This mainly caused bad skiing at Mt Hood. About 10-12 inches of melting, consolidation and stabilizing of the total snowpack was also seen at Mt Hood.

The last system in the series crossed the south Cascades late Monday. This caused strong winds and heavy snow in the above treeline at Mt Hood.

The Meadow pro-patrol reports 15 inches of new snow at 6600 feet on Tuesday. Avalanche control gave numerous up to 14 inch size 1-2 wind and storm slab avalanches but with limited propagation.

The mid and lower snowpack at Mt Hood should consist of layers of stable consolidated rounded grains or melt forms and crusts from multiple warm periods this winter.

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.