Avalanche Forecast

Archived

Feb 2nd, 2018–Feb 3rd, 2018

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Regions

Mt Hood.

Large and destructive Wet Slab avalanches may occur above treeline. Avoid traveling on or below avalanche terrain originating at higher elevations. Avalanches may travel into lower elevation bands and reach valley bottoms. Stay off avalanche terrain where being caught in even a small Loose Wet avalanches could have dire consequences such as above cliffs, open creeks, or gullies.

Detailed Forecast

Continued warm and wet weather will maintain avalanche hazard in the Mt Hood area Saturday.

Above treeline areas will receive rain for the first time since early January. Rain falling on deep dry wind slabs may produce large and destructive slab avalanches. Wet Slabs are extremely difficult to predict. However, if they release they will entrain significant amounts of snow and travel into lower elevation bands. Avoid steep open slopes above treeline and limit your exposure to avalanche paths that originate at higher elevations.

Near and below treeline, rain on wet snow will maintain the possibility for Loose Wet avalanches. These avalanches are most likely during and following higher intensity rain showers. Avoid steep open slopes above terrain that could magnify the consequences of an avalanche. Cliffs, open creeks, rocks, and gullies are all examples of terrain traps where small avalanches may injure or kill you.

Snowpack Discussion

Warm wet weather has created wet surface snow conditions well into near treeline terrain in the Mt Hood area. At elevations receiving snow, SW winds continued to build wind slabs on lee slopes.

The upper snowpack consist of a mix of wet snow, old crust, and well consolidated storm snow. Observations demonstrate a strong and well bonded upper snowpack.

Observations

On Thursday, NWAC pro-observer Laura Green traveled in Newton and Heather Canyons. She found light rain beginning to wet the snow surface by mid-afternoon. Winds were increasing throughout the day.

On Wednesday, Mt Hood Meadows Pro Patrol reported the surface snow was sculpted by recent winds creating variable snow surfaces and scoured ridgelines. Below treeline, 6-8" of snow was well bonded to the 1/29 semi-supportable crust.

Mt Hood Meadows Pro Patrol Sunday reported multiple very large artillery-released avalanches with crowns up to 12 ft range, running on steep NE and ENE terrain above treeline and travelling very long distances, in one case snapping 20+ year old trees.

Problems

Wet Slabs

Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.

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.