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Avalanche Forecast

Archived

Jan 21st, 2020–Jan 22nd, 2020

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural and human triggered avalanches likely.
Treeline
Natural and human triggered avalanches likely.
Below Treeline
Natural avalanches possible, human triggered probable.

Regions

Mt Hood.

Dangerous avalanche conditions exist. The likelihood of triggering a large and dangerous avalanche will increase throughout the day and peak when snow turns to rain at most elevations on Wednesday evening. Avoid slopes steeper than 35 degrees and pay close attention to warming temperatures which will drastically increase avalanche hazard.

Discussion

A storm approaches Tuesday night and should lay down significant snowfall before turning to rain Wednesday afternoon/evening. Avalanche hazard will increase sharply as the temperatures rise. There is some uncertainty when the transition from snow to rain will occur, so pay close attention to signs of warming, such as rollerballs of snow, many trees beginning to shed snow or drip water. When you notice these signs of warming the avalanche hazard is about to peak, so avoid avalanche terrain.

(Click the Photos & Regional Synopsis tab above for some pics of a very large avalanche on the Newton Headwall from last week)

Snowpack Discussion

New Regional Synopsis coming soon. We update the Regional Synopsis every Thursday at 6 pm.

Clearing on Sunday offered the first look at the upper mountain after an active 10 days of weather. A very large avalanche was observed on the Newton Headwall. It likely occurred during the storm last week, but highlights continued uncertainty about the snowpack at upper elevations.

A very large crown around 10,000’ on the Newton Headwall of Mt Hood which likely occurred during the storm last week. Photo: Kevin Kayl

Debris from the Newton Headwall avalanche in Newton Canyon. Debris filled the valley floor and extends to 5000’! Photo: Nick Burks

Problems

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). 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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.