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Avalanche Forecast

Archived

Feb 5th, 2016–Feb 6th, 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 unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Mt Hood.

New wind and storm slab layers should be seen on Saturday. The skiing should be improved but don't forget to make careful snowpack evaluations.

Detailed Forecast

Strong southwest winds aloft will accompany a cold front will cross the Northwest on Friday evening. West winds will follow with orographic snow showers and a good cooling trend on Saturday morning.

The cooling trend may help bond new snow to old snow surfaces where the snow starts at above freezing temperatures. With a little luck many areas along the west slopes will have about 5-10 inches of new snow by the time snow showers taper off on Saturday.

The main avalanche problem should be new wind slab on lee slopes in the near and above treeline. Watch for signs of snowpack cracking and firmer wind transported snow on lee slopes.

A secondary avalanche problem should be new storm slab in areas with less wind if there is rapid loading. The cooling trend may help limit this avalanche problem.

 

 

Snowpack Discussion

Weather and Snowpack

A strong occluded front with strong winds crossed the Northwest January 29-30th. NWAC stations on Mt Hood received about 1.5 feet of new snow

Cool and benign weather settled over Mt. Hood Sunday to Tuesday with ample sunshine on Tuesday. A sun crust likely formed on solar slopes.

A cold front and then a warm front crossed the Northwest on Wednesday and Thursday. NWAC stations at Mt Hood for the 2 days ending Friday morning had 18-20 inches of snowfall.

Recent Observations

The Meadows pro-patrol Thursday reported heavy snowfall and remotely and easily triggered widespread 1 foot wind slab mainly on north to southeast slopes along with storm slab in the near and above treeline. A combination of storm slab, loose wet avalanches and rollerballs was seen below treeline.

A couple reports for Mt Hood are available via the NWAC Observations page from Mt Hood on Thursday with easy pit tests for storm layers or on the crust buried January 29th. Roller balls due to warm temperatures were reported below the snow level.

The Meadows pro-patrol reported less activity today with isolated wind or storm slab released by explosives or ski cuts in the near and above tree line.

 

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.

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.