Avalanche Forecast
Regions: Mt Hood.
Recent deep storm and wind slab deposits should be given ample time to settle and stabilize, especially due to the slow stabilization rates given the expected cold temperatures. Human triggered avalanches should remain likely on Monday. Choose low angled terrain and avoid slopes connected to avalanche paths with wind loaded start zones. More deeply buried persistent layers are now a factor!
Detailed Forecast
With additional recent storm snow of 2-3 feet or more by Monday, in combination with recent moderate to strong SW-W winds, expect avalanche activity to be slow to improve. Human triggered avalanches should remain likely Monday.  Dangerous avalanche conditions should persist Monday, especially in all wind loaded terrain. Storm slabs will likely fail within storm layers, but in some areas storm slabs may step down to deeper layers. Choose low angled terrain and avoid slopes connected to avalanche paths with wind loaded start zones.
Even though the lower part of the below treeline band is filling in, watch for early season travel hazards such as barely covered rocks and open creeks.
Snowpack Discussion
Weather and Snowpack
An active and cool weather pattern has resulted in a snowy December thus far with Mt. Hood NWAC stations, recording an impressive 4-7 feet of snow!
Cold and fair weather was in place midweek allowing near surface faceting and/or surface hoar to become widespread. Beginning Wednesday night and continuing through Thursday, considerable wind transport from easterly winds occurred near and above treeline.Â
Moderate easterly winds shifted to the west along with a rapid warming trend Thursday night along with about 7 inches of new snow through early Friday morning. Another 10 inches slowly accumulated through early Saturday morning. WSW winds were rising as of Saturday afternoon.  Additionally, 14-17 inches were reported Sunday morning, with about another 12 inches deposited during the day Sunday! It's deep out there.Â
Prior to this new snow, the snowpack in non-wind affected terrain was generally right side up with low density snow at the surface and no problematic layers in the lower snowpack. A freezing rain crust that formed and was buried December 2nd has been identified in the snowpack up to 7000 ft, but no new or recent avalanche activity has been reported on this layer.Â
Recent Observations
During the day on Wednesday the Mt. Hood Meadow pro patrol reported light winds that were not causing wind transport. The upper snowpack was generally right side up with good skiing and riding conditions. Some surface hoar was noted in wind sheltered locations.
On Thursday shifting winds was producing significant wind transport of recent low density snow near and above treeline on Mt. Hood. Despite a rapid warming trend, shifting winds and new snowfall Thursday night, widespread avalanche activity was not reported Friday morning from the Mt. Hood Meadows pro-patrol. Pro-observer Laura Green found sensitive storm layers in the below and near treeline bands in snowpack tests, but experienced no direct signs of instability. No observations were received from above treeline where lee aspects should have been continuously loaded throughout the day on Friday.Â
Meadows patrol Sunday reported triggered soft slab avalanches were sensitive and releasing 6-12 inches in areas previously controlled. However, control work in Heather Canyon for the first time since the storms began Thursday, also produced soft slabs up to about 1 foot crowns. By Sunday afternoon, slopes that had released early in the morning were already reloading and producing ski sensitive soft slabs up to about 6 inches.Â
Imagine in areas void of avalanche control! Storm slabs of 1-3 feet seem likely.
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: 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