Avalanche Forecast
Regions: Mt Hood.
If travelling into the near and above treeline elevation bands Wednesday, watch for lingering wind slab on lee aspects and loose wet avalanches on solar aspects.
Detailed Forecast
Freezing levels on Wednesday should continue the gradual rising trend that began on Tuesday. Increasing high and mid clouds should be seen in the afternoon.Â
Recent shallow storm snow should continue to settle, but filtered sunshine and increasing temperatures may activate loose wet avalanches predominately on steeper southerly slopes near and above treeline. There likely isn't enough snow on southerly aspects near and below treeline for significant wet loose danger.  Â
Also, there may be pockets of sensitive wind slab mainly on N-SE aspects near and above treeline. Â
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Snowpack Discussion
Strong southwest flow carried a warm and wet front across the PNW Saturday night. This front tapped subtropical moisture pushed snow levels pretty high on Mt. Hood and resulted in 3.5 - 4.5 inches of rain at NWAC sites. A cooling trend Sunday along with another inch of water ended as 4-5 inches of new snow between 5-6000 feet by Monday morning.Â
Mt. Hood pro-patrol reported wind transport Sunday night and Mon AM leading to a thin wind slab above treeline producing small but regular releases during control work on lee slopes around 7000 ft. West winds eased off more quickly than forecast Monday and new wind transport was likely insignificant. They also reported the storm snow was well bonded to the most recent rain crust.
Light winds and slowly rising freezing levels on Tuesday should have helped further stabilize the upper snowpack.
The mid and lower snowpack at Mt Hood should also mainly consist of melt-freeze crusts and stabilized rounded grain layers from warm stretches so far this winter.Â
Avalanche Problems
Storm Slabs
Release of a soft cohesive layer (a slab) of new snow that breaks within the storm snow or on the old snow surface. Storm-slab problems typically last between a few hours and few days. Storm-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.
You can reduce your risk from Storm Slabs by waiting a day or two after a storm before venturing into steep terrain. Storm slabs are most dangerous on slopes with terrain traps, such as timber, gullies, over cliffs, or terrain features that make it difficult for a rider to escape off the side.
Storm slabs usually stabilize within a few days, and release at or below the trigger point. They exist throughout the terrain, and can be avoided by waiting for the storm snow to stabilize.
Aspects: South East, South, South West.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1
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: North, North East, East, South East.
Elevations: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1