Avalanche Forecast
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.
Avalanche Problems
Wind Slabs
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.
Wind Slabs form in specific areas, and are confined to lee and cross-loaded terrain features. They can be avoided by sticking to sheltered or wind-scoured areas..
Wind Slab avalanche. Winds blew from left to right. The area above the ridge has been scoured, and the snow drifted into a wind slab on the slope below.
Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.
Aspects: North, North East, East, South East, South.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1 - 1
Storm Slabs
Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. 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.
You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.
Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1 - 1