Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Dec 27th, 2014–Dec 28th, 2014

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

It may 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.

Detailed Forecast

Northwest winds and snow showers should remain a bit stronger and heavier at Mt Hood through Sunday morning than the rest of the forecast area with a cooling trend. Approximately a foot of new snow should be seen at Mt Hood by Sunday morning with several more inches by the end of the morning.

The main avalanche problems Sunday should be new storm and wind slab. Storm slab will occur in areas that receive more than an inch of snow an hour for several or more hours. For wind slab watch for firmer wind transported snow on lee slopes. Both problems are likely at Mt Hood on Sunday.

The surface hoar will increase instability where it gets buried intact. You can check for this layer using hand shear tests or shovel tilt tests.

It may 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 warm storm moved over the Northwest Tuesday and Wednesday with strong west winds followed by lowering snow levels. About 5-13 inches of snow was seen at NWAC at Mt Hood at the tail end of the storm.

New NWAC observer C.J. Svela reported wind transport Wednesday in White River Canyon in the near and above tree-line elevation bands. This gave cracking on wind loaded slopes and sensitive cornices in the canyon. 

The Mt Hood Meadows patrol reported a post control release Thursday where northwest wind loaded unusual lee slopes. A skier triggered a 40-60 cm wind slab avalanche in bounds where stiffer snow overlaid a weaker layer at 6600 feet on a south aspect.  

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.