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Avalanche Forecast

Archived

Jan 10th, 2016–Jan 11th, 2016

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Mt Hood.

New small shallow storm and wind slab seem possible by the end of the day at Mt Hood on Monday. Evaluate snow and terrain carefully on Monday. Adjust your plans if winds are stronger or new snowfall is heavier than expected.

Detailed Forecast

A front should weaken as it moves over the Northwest on Monday. At Mt Hood this should bring moderately increasing southwest alpine winds and light occasional moderate rain or snow Monday morning changing to showers Monday afternoon with lowering snow levels.

Wet surface snow from Sunday should refreeze on Monday. 

New small areas of shallow storm slab seem possible mainly on the volcanoes. The limited amounts of new snow and the cooling trend should limit the extent and depth of new storm slab by the end of the day.

New small areas of shallow wind slab also seem possible mainly on lee slopes on the volcanoes by the end of the day. The limited amounts of new snow and the cooling trend should also limit the extent and depth of new wind slab.

 

Snowpack Discussion

About a week of fair weather was centered around the New Year. This allowed the heavy snow that fell during the strong storm cycle that ended about Christmas to settle and stabilize.

By New Years Eve through last weekend moderate to strong east-northeast winds had significantly scoured most of the available surface snow, mainly in the near and above treeline elevation bands.

Surface snow sculpted by recent wind and active wind transport. Photo: Laura Green

Last Monday the Mt Hood Meadows pro patrol reported warming and a widespread 1 cm freezing rain crust up to 7000 feet. This was followed by about 8-10 inches of snow at Mt Hood early last week.

Laura was out again near the Mt Hood Meadows ski area last week and reported 5 inches of storm snow had formed small slabs, non-reactive to ski cuts, but some explosive triggered slides up to 10 inches were seen on steep slopes of varied aspects. These shallow slabs were becoming less sensitive by Wednesday.

No avalanches have been reported over the past several days on Mt Hood.

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.