Avalanche Forecast

Skies may partially clear Friday or feature filtered sunshine in the afternoon as a frontal system lifts north into British Columbia. Freezing levels should rise to around 10,000 ft Friday and alpine winds should fall off during the day.  Unlike the Washington Cascades, Mt. Hood will have significant storm related avalanche danger Friday. 

Winds slabs will be found near and above treeline Friday and should be sensitive to human triggering. Avoid wind loaded slopes and watch for obvious clues like snowpack cracking. As winds veer to northerly above treeline Thursday night, snow will be transported to SW aspects. 

Storm slab instabilities should be quick to settle out on Friday, but look for the greatest sensitivity through mid-day or in areas where graupel layers accumulated during heavier showers Thursday afternoon and may act as a bed surface. 

Small loose wet avalanches are possible on steeper slopes involving new snow storm especially near and below treeline. Watch for wet snow deeper than your boot tops, especially on steep solar slopes during the late morning to afternoon hours. Even if skies remain mostly cloudy, strong solar input in mid-April will affect the snow surface on solar slopes.  

The potential for cornice releases should be low Friday but will increase through the weekend. Cornice releases can be unpredictable during the spring so avoid areas below cornices and remember that cornices can break much further back than expected along ridges.

Although not listed as an avalanche problem, large, powerful glide avalanches can release unexpectedly so avoid areas below steep unsupported slopes or rock faces showing glide cracks.

Weather and Snowpack

We've had two big warm-ups and spring shed cycles since the end of March. Over this time period the snowpack has undergone significant settlement with lower elevation snow beginning to fade away and with an overall transition to a spring snowpack.

On Tuesday afternoon and night a frontal system brought a few inches of snow to the Mt. Hood area. A low pressure system brought another round of snow Wednesday night and Thursday with 6-8 inches of new snow seen at the Timberline and Mt. Hood Meadow NWAC stations through Thursday afternoon. Winds were moderate out of the S or SW above treeline Thursday transporting new snow to lee slopes. 

After a relatively cool week, the upper snowpack has generally drained and refrozen near and above treeline and on non-solar aspects. However it's quite variable how supportable the underlying crust is throughout the terrain. At lower elevations and on solar aspects, wet grains likely remain dominant in the upper snowpack.  

Frequent March storms built unusually large cornices along many ridges. The potential for low probability/high consequence encounters, such as cornice failures and glide avalanches from steep unsupported slopes and smooth rock faces will continue through the spring. 

The mid and lower snowpack along the west slopes should generally be a stable mix of crusts and layers of moist and rounded snow crystals.

Recent Observations

Mt. Hood Meadows pro-patrol reported small wind slabs building on lee N-NE aspects Thursday above treeline that were sensitive to ski cuts and easily showed cracking and propagation. In the deepest areas, the slabs were locally up to 2' by mid-day Thursday.