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 15th, 2015–Dec 16th, 2015

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

Regions

Mt Hood.

Previous wind and storm slab layers from the weekend should be the main concerns on Wednesday. Greater caution would be necessary if the weak front Tuesday night and Wednesday morning brings more snow than expected.

Detailed Forecast

A weak cold front will cross the Northwest Tuesday night and Wednesday morning. This may bring some very light amounts of new snow but should not greatly change conditions. Some fair weather should be seen by Wednesday afternoon. Light or moderate northwest winds and cool temperatures should also continue on Wednesday.

Previous wind slab layers will likely linger on previous lee slopes near ridges and summits or on unusual south aspects on Wednesday. Storm slab from the weekend might still be possible Wednesday but would be found in what were calmer areas if it still exists.

Use more caution and watch for new small wind slab or small storm slab if the weak front Tuesday night and Wednesday morning brings more snow than expected.

Terrain anchors are still causing significant anchoring at the lowest elevations. Use caution near creeks which are still open in some areas.

Snowpack Discussion

An atmospheric river caused warm very wet weather last week. About 5-7 inches of rain was seen at Mt Hood. This caused an avalanche cycle, consolidation and stabilizing of the older part of the snowpack.

A stormy pattern with cooling was seen late last week and over the weekend with about 4-5 feet of snowfall at Mt Hood.

The Meadows pro patrol on Sunday reported sensitive explosive releases on most lee slopes up to 6600 feet as travel above that was avoided. Numerous soft slabs ran 100% of the paths and traveled far distances releasing in storm layers. These avalanches were on previously heavily skied paths indicating backcountry areas would likely have significantly deeper slab potential. The Meadows pro patrol on Monday still reported avalanches of increasing size with increasing elevation. At 6800 feet avalanche control triggered a 3-5 foot hard wind slab on a northeast slope which release on the rain crust from last week. Ski cuts generally gave just isolated 6-8 inch releases. The Meadows pro patrol on Tuesday reported that wind Monday night had greatly rearranged the snow into sastrugi and wind slab down to the below tree line zone. But no avalanches were triggered or reported. The winds at the NWAC Meadows weather station were northerly the past 24 hours so wind slab may be found on unusual aspects. So wind slab will also be indicated on south aspects in the avalanche problems.

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.