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Avalanche Forecast

Archived

Jan 28th, 2016–Jan 29th, 2016

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

Mt Hood.

On Mt Hood the  main problem Friday, is expected to be wind slab in near and above treeline zones. Wet snow conditions may be slow to refreeze and strengthen at lower elevations.

Detailed Forecast

Another front should arrive Friday, bringing additional moderate snowfall at lower snow levels. Winds should be strong, especially near and above treeline. The main concern Friday will be newly forming wind slab on lee exposed slopes, especially NW-N-SE facing near and above treeline. 

With cooling temperatures, the new snow should have a favorable profile.

 

Snowpack Discussion

A warm front last Thursday caused heavy rain on the volcanoes but with lighter rain at Mt Hood. This caused an avalanche cycle and consolidation along the Cascade west slopes and Mt Hood.

This was followed by cooler weather and some snow. NWAC stations at Mt Hood indicate about 6-9 inches for the 2 days ending Sunday morning.

The Mt Hood Meadows pro patrol Sunday near tree line reported isolated 2-6 inch storm slabs released by ski cuts on lee N-NE slopes. A stable surface crust was reported below tree line.

The Mt Hood Meadows pro patrol Monday reported some roller balls on solar slopes but no avalanches. There was about 6-8 inches of loose snow on non solar slopes in the near and above treeline.

Very mild, above freezing weather Wednesday allowed for wet surface snow conditions in most areas.

Mild weather continued Thursday with heavy rain reaching at least 8000 feet on Mt Hood, causing increasing wet snow conditions. 

Snow levels dropped late Thursday as temperatures lowered some 10 degrees or more through the day. This has changed rain to snow gradually, likely allowing a favorable bond to form between new snow and the old wet snow surface.

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.