Avalanche Forecast
Regions: Mt Hood.
Watch for wind transported snow on a wide variety of non-traditional aspects and features Monday. Building wind layers may be touchy and cautious travel conservative decision making is essential in wind exposed terrain. Watch for sluffs or triggered, loose dry avalanches on steep sheltered terrain, especially above terrain traps such as creeks, cliffs or gulleys.
Detailed Forecast
Snow showers should end overnight Sunday, giving way to partial clearing and continued cold temperatures. Strong NE-E ridgetop winds should continue to transport the ample loose surface snow and build touchy wind slabs on more non-traditional or unusual SE-SW aspects, mainly above tree line and possibly near tree line.
Deep, low density snow will make sluffs or loose slides likely on steep wind sheltered slopes. Watch for travel on steep slopes above terrain traps, such as cliffs or creeks where the entertainment of loose snow may bury someone caught more deeply.Â
Fresh, touchy wind slabs near ridges and non traditional aspects, will be the primary avalanche problem on Monday. Wind affected snow should be widespread Monday, especially with strong shifting winds, watch for wind transported snow on a variety of aspects and cross loaded features.
Snowpack Discussion
Weather and Snowpack
Strong storms around the Solstice deposited generally 3 inches of water equivalent at NWAC stations on Mt Hood. Unfortunately, much of the heavy precipitation fell in liquid form with rain reaching above 7000 feet.
A strong front and strong west flow aloft was seen over the Cascades on Monday and Tuesday. NWAC stations at Mt Hood had strong west winds and the station at Mt Hood Meadows had about 2.5 feet of new snow for the 48 hours ending Wednesday morning.
A warm front draped over the north Washington Cascades Thursday left Mt. Hood in the warm sector with temperatures pushing above freezing at most stations under mostly sunny skies. When the front finally sagged south Thursday night, very light rain and snow moved in with a breakable rain crust reported up to 6600 feet Friday morning in the Meadows area.
A period of warming Friday and early Saturday has strengthened the surface crust, reported to at least 7200 feet above Mt Hood Meadows on Saturday.Â
A very cold storm arrived New Year's Eve continuing through New Year's Day, depositing 10-15 inches or more of low density snow, ringing in the New Year in style! The snow arrived with cooling temperatures, but moderate winds in the upper elevations.
Recent Observations
Reports from the Mt Hood Meadows pro-patrol following the Solstice indicated a significantly different snowpack following rain, avalanches and cooling. A stout surface crust was found at all elevations up to at least 7200 feet. On exposed terrain, the crust was very supportable while in treed terrain the crust ranged from breakable to supportable.
The pro-patrol at Mt Hood Meadows Tuesday reported very sensitive storm slab releases, with slabs releasing upon approach to ridges or steeper features.
The pro-patrol on Wednesday reported below treeline widespread sensitive 6-12 inch storm slab releasing by ski tests. Near tree line wind slab became reactive to 1-1.5 feet with good propagation. Above treeline explosives were used with larger hard deep wind slab releases where ski tests were considered too dangerous. One very large hard slab released with explosives was rated R4 - D3.5 with an average crown depth of 4-6 feet with a maximum of 8 feet down to the Solstice crust. Again, this avalanche released with explosives and this size result was not repeated during control work Wednesday but impressive nonetheless!  Wind slab near and above treeline was seen mainly on E-SE slopes Wednesday.
A strong surface crust was reported Saturday, 12/31 to at least 7300 feet.
No reports were received New Year's.
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: All aspects.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 1