Avalanche Forecast

Here we go again! With another round of moderate to occasionally heavy snow forecast Saturday night and Sunday, 24 hr snowfall totals on Mt. Hood through Sunday 4 pm should average 18-24 inches with snow levels remaining relatively stable. W-SW transport winds should stay moderate near and above treeline through Sunday evening, continuously stripping windward slopes and loading lee aspects.

With this latest round of snowfall, we are expecting avalanche activity to become widespread, with natural avalanches likely and human triggered very likely. Wind loading of lee slopes will push the avalanche danger to High near and above treeline, but expect sensitive conditions in all bands. Avoid all wind loaded terrain Sunday. Storm slabs will likely fail within storm layers due to rapid loading, 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.

Weather and Snowpack

An active and cool weather pattern has resulted in a snowy December thus far with Mt. Hood NWAC stations recording about 3-5 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. 

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.    

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. 

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.