Avalanche Forecast
Regions: Mt Hood.
The avalanche danger should gradually increase through the day Thursday as new storm snow is deposited and wind slabs begin forming on the lee, higher elevation terrain. Cautious route-finding and terrain selection will be essential Thursday at higher elevations near or above treeline to stay safe and avoid storm related avalanche problems.
Detailed Forecast
The next in a series of frontal systems should arrive during the day Thursday, causing increasing light to moderate snow and winds, at relatively cool temperatures. Â
New shallow storm or wind slabs may form by late Thursday, causing a gradual increase in danger.  Cautious route-finding and terrain selection will be essential on Thursday, especially above tree line.Â
Particular caution should be used on steeper terrain, giving additional storm instabilities time to settle. Look for wind slab on a variety of aspects near and above treeline due to shifting winds. Watch for signs of firmer wind transported snow that can indicate wind slab layers near and below ridges.
Snowpack Discussion
Fair weather was centered around the New Year, allowing the heavy snow that fell prior to Christmas to settle and stabilize. Moderate to strong east-northeast winds in early January had significantly scoured most of the available surface snow in the near and above treeline elevation bands.
Warming associated with the storm Tuesday and early Wednesday caused rain or mixed rain and snow to near tree line by early Wednesday before cooling dropped the snow levels by later Wednesday. Strong winds above treeline and water equivalents of nearly 2 inches have formed extensive hard slab conditions on lee slopes above treeline. Howitzer control results Wednesday produced hard slab avalanches on lee slopes well above treeline above Mt Hood Meadows, though human triggering a similar slide is unlikely.Â
 Near and below treeline, more shallow and isolated pockets of wind slab produced smaller slides with explosives, mostly 8 inches.
Cooling through the day Wednesday has allowed for previously wet surface snow to begin forming crusts, while allowing storm or wind slabs to gradually stabilize.
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.
Elevations: Alpine, Treeline.
Likelihood: Possible
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: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1