Avalanche Forecast

Partly or most cloudy weather should be seen at Mt Hood on Sunday with moderate west winds. A slight warming trend should be seen by Sunday afternoon.

A broad brush will be used on Sunday and all aspects will be indicated for wind slab due to recent varied wind directions. Watch for firmer wind transported snow on all aspects especially above treeline.

The danger of snow immersion may not be past due to all the heavy snowfall in December. Always ski or ride with a partner and keep them in sight at all times especially if you are moving past trees.

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.

Note that the first in a series of storms is expected to begin to move across the Northwest Sunday night. This will bring a significantly increasing avalanche danger by Monday.

Weather and Snowpack

The last storm cycle to affect all of the Olympics and Cascades 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.

But a system moved across the Mt Hood area late Wednesday through Thursday morning depositing an additional foot of new snow with moderate southeast winds shifting to the west and decreasing. 

Fair and cold weather in between and following these systems has been seen at Mt Hood 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.

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

W-NW winds in the 20-30 mph range are seen some higher elevation NWAC stations on Saturday such as the Magic Mile at Timberline. These winds are strong enough to transport snow to mainly NE to SE aspects.

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

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, the pro-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. 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!

NWAC pro-observer Laura Green was out in the Newton and Clark drainages on Friday a found a mix of surface conditions of recent snow and 3-4 mm surface hoar with a thin sun crust on solar slopes. The upper snow pack on N-NE slopes was right side up with no direct signs of instability.

The Mt Hood Meadows pro-patrol on Friday had less activity on control with only some local explosively controlled wind slab on NE slopes above 6500 feet and nothing from ski tests on test slopes. Small triggered loose dry avalanches were seen below treeline.

A report via the NWAC Observations tab also indicated a small slab avalanche near the Ski Bowl ski area on Friday.