Avalanche Forecast
Regions: Mt Hood.
A peak in the avalanche danger should be seen Tuesday. You may encounter a greatly increasing avalanche danger with elevation on Tuesday. Avoid travel in terrain connected to higher start zones.
Detailed Forecast
Increasing strong southwest flow aloft will carry a major deepening low pressure system and cold front across the Northwest on Monday and Tuesday. Expect very strong alpine winds Monday night and Tuesday at Mt Hood, about 8-12 inches of new snow above treeline by Tuesday early morning, and more heavy new snow at lowering snow levels Tuesday.
New wind slab will form on lee slopes mainly near and above treeline Monday night and Tuesday morning. This is most likely on northwest to southeast aspects but is possible on other aspects. Watch for firmer wind transported snow. Due to the strength of the winds winds extensive wind slab is likely.
 New storm slab is likely to form above treeline Monday night and then to the near and below treeline Tuesday in areas with rapidly accumulating new snow.
 A peak in the avalanche danger should be seen Tuesday. You may encounter a greatly increasing avalanche danger with elevation on Tuesday. Avoid travel in terrain connected to higher start zones.
The recent warm weather has melted much of the early season snowpack. Expect terrain hazards with poorly covered rocks, vegetation and creeks, particularly on south-facing terrain at lower elevations, and on exposed ridges where wind events have stripped much of the seasons snowcover.
Snowpack Discussion
The warm and sunny weather the first half of December did a number on the early season snowpack at Mt Hood, gradually consolidating snow and returning many areas to very shallow early season conditions. The most consistent snowpack remains on shaded northerly aspects in the upper below treeline to near treeline.
Above freezing temperatures, windy conditions, and periods of light rain over the weekend likely erased persistent grain types that were observed prior to Friday on Mt. Hood.
The overall snowpack is stable with settled old snow sitting over the strong Thanksgiving rain crust, buried about 1-3 feet.
Observations
No human-triggered avalanches have been reported in over a week.Â
But on Monday the Meadows pro patrol reported a major freezing rain event with up to 6-8 inches of ice in the 6000-7300 foot elevation range, with rain softened snow at lower elevations.
Ice coated tree limbs at Mt Hood Meadows on Monday December 18th. Photo Nick Burks.
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, North West.
Elevations: Alpine, Treeline.
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: Likely
Expected Size: 1 - 1