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Avalanche Forecast

Archived

Dec 28th, 2014–Dec 29th, 2014

Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
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.

High danger now expected on Sunday at Mt Hood.

Detailed Forecast

Northwest winds and heavy snow is being seen at Mt Hood on Sunday.About 15 inches of storm snow has accumulated since the storm began yesterday.Snow is much heavier at Mt Hood Sunday than the rest of the forecast area.

With these snowfall and loading rates new storm and wind slab is certain on Sunday. Back country travel in avalanche terrain is not recommended especially in the near and above treeline on Sunday. The surface hoar will increase instability where it gets buried intact.

It will also take longer for some stabilizing at Mt Hood than the rest of the forecast area since stronger winds and heavier snowfall should last longer there on Sunday.

Snowpack Discussion

A cooler period with little precipitation was seen about Thursday to Friday. Some skiers were reporting better conditions on lower angle slopes with skis scraping crusts on some steeper slopes. Surface hoar is possible from Thursday night.

 A cold front is moving over the Northwest on Saturday and Saturday night causing west winds and moderate to heavy snow and snow showers and a cooling trend. This should build some new wind and storm slab especially at Mt Hood by Sunday.

 

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.

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.