Avalanche Forecast

Avalanche danger will increase sharply at higher elevations on Thursday as a moist southerly flow brings a forecast 8-12" of new snow above 6,000 ft with a snow line working rapidly down the mountain on Thursday. Moderate winds occasionally becoming strong above treeline will transport the new snow on Wednesday night and Thursday.

You are likely to trigger a sensitive and increasingly large Wind Slab above treeline and it will be possible to trigger a smaller Wind Slab near treeline into the upper part of the below treeline band, particularly by the end of the day on Thursday as dry snow falls to much lower elevations. Watch for signs of instability including wind-stiffened snow and cracking of the snow surface or signs of active snow transport including snow filling in tracks, snow pillows with firmer snow, and crusts exposed on ridge-tops. If you find any of these, avoid wind-loaded slopes and slopes steeper than 35 degrees.

Rain overnight below 5000-6000 ft may cause some water to be absorbed by the snowpack. While Loose Wet avalanches are not forecast to be a problem on Thursday given cooling temperatures and ample time for snow settlement, if wet snow conditions exist in your area and you find your boots penetrate more than 6" into the snow, then avoid steeper terrain.

Up to 0.1" of water fell during shower activity on Wednesday with a snow level of approximately 6,000 ft and given the warm temperatures it dissolved into the existing snow surfaces: A breakable crust (1-3 mm) on non-polar aspects formed during several days of melt-freeze cycles Monday and Tuesday or settling dry snow on shaded aspects. S-SW winds were increasing and approaching the moderate range by the end of the day near treeline. 

Friday night and Saturday brought 9 inches of snow in the Timberline area, with only a few inches of new snow in the Mt Hood Meadows. The new snow fell with cool temperatures and some moderate westerly winds near ridge crest Friday night. This now settled snow sits atop another melt-freeze crust.

Several melt-freeze cycles the weekend of March 10-11 helped to consolidate the snowpack.

While we are tracking several layers deeper in the snowpack, there are currently no significant layers of concern.

Observations

On Wednesday, MHM pro patrol reported a thin crust on non-polar slopes with 3-4” of old cold snow on shaded slopes and the afternoon precipitation dissolved into existing snow surfaces.

On Tuesday, MHM pro patrol reported shaded terrain holding soft snow while the sun was softening snow surfaces on non-polar aspects. Very minor loose wet activity was reported below treeline. He noted that the NWAC Cascade Express station at MHM was reading higher than observed temperatures on Tuesday due to its proximity to a dark roof surface.

On Sunday, MHM pro patrol reported no reactivity to any older shallow wind slabs with only very shallow surface snow becoming moist. 

On Friday, Pro-observer Laura Green found 2-4" of new snow near Timberline well bonded to the underlying crust. Poor visibility limited observations above treeline.