Avalanche Forecast

A weak disturbance will move across the region Saturday, causing moderate to strong NW ridge level winds may build new fresh wind slabs on lee slopes, near and especially above treeline. 

Light snow showers Saturday may bury intact a variety of weak surface snow types formed this week under fair cold weather.

Local wind slabs from the recent E-NE winds are likely Saturday. This should be mainly on westerly to southeasterly aspects near ridges.

Watch for firmer wind transported snow on all aspects, mainly near and especially above treeline.

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

The last significant storm cycle to affect the Mt Hood area was from late Thursday, December 8th through Monday morning, December 12th. About 4 feet of snow were recorded at the NWAC stations in the Mt Hood area ending Monday morning Dec. 12th. 

Fair and cold weather this week has been interspersed with periods of moderate N-NE-E winds both Wednesday and again Friday. These winds were strong enough to build fresh wind slabs on more atypical SW-NW facing terrain, mainly near and especially above tree line.

A system moved across the Mt Hood area late Wednesday through Thursday morning, depositing an additional foot of new snow along with moderate winds.

There has been about 12 inches of snowpack settlement since Monday, allowing underlying or storm snow related weak layers to stabilize. 

Several clear nights with light winds this week have allowed for weak surface snow development. On wind and sun sheltered terrain, extensive near surface faceted snow or surface hoar have formed this week and this may be an important weak layer if buried intact by the expected return of light snowfall Saturday.

A thin sun crust is likely to have formed on steeper southerly facing slopes, which also may be a future interface for avalanches when loaded with sufficient wind transported or future storm snow.

Recent Observations

A regional avalanche cycle was seen December 8th-11th especially along the west slopes with some avalanches releasing on the December 8th persistent weak layer in the Washington Cascades. 

Since Monday, in areas not experiencing strong east winds Wednesday, there has been significantly less avalanche activity throughout the region as storm layers continue to stabilize.   

Following the most recent 12 inches of new snow Thursday morning, patrol at Mt Hood Meadows, indicated new wind slab was sensitive to ski trigger even on lower angled slopes. These avalanches, about 1 foot crowns, released above tree line on mainly E-NE facing terrain.

By Friday, the recent wind slabs were observed to be less reactive. However, exposed terrain near and especially above treeline should be met with caution. 

Near and below treeline, the unconsolidated new snow was well bonded to the old surface and no avalanches were noted, but ski conditions of excellent quality were noted! 

There are a variety of current snow surface types awaiting our next storm snow, including surface hoar, near surface faceted snow, sun crusts, wind sculpted snow, and low density snow in protected areas.