Avalanche Forecast
Regions: Mt Hood.
Fresh wind slab will build on lee easterly aspects near and above treeline, but expect cross-loading due to the strength and duration of the winds. New wind loading will create dangerous avalanche conditions mainly near and above treeline Friday.
Detailed Forecast
Mt. Hood will be spared the heavier precipitation seen further north but not the strong winds or warming trend. Â Light rain or snow should develop overnight and increase by Friday late afternoon and evening as a cold front sweeps through. Moderate to strong southwest winds will increase Thursday night and stay elevated through Friday night. Â Â
Fresh wind slab will build on lee easterly aspects near and above treeline, but expect cross-loading and wind slab formation band due to the strength and duration of the winds. New wind loading will create dangerous avalanche conditions near and above treeline Friday.Â
Shallow storm slab should build and become more reactive late Friday afternoon due to increasing snowfall paired with a warming trend. Â
Generally shallow loose wet avalanches are possible below treeline due to rainfall at lower elevations.Â
Snowpack Discussion
Weather and Snowpack
The most recent wet warm storm arrived on Valentines Day 2/14 and formed the uppermost very strong rain crust in our snowpack.Â
A stronger than forecast storm late Monday through Tuesday deposited 2 - 2.5 ft of snow by Tuesday evening. The heavy snowfall arrived with very strong westerly alpine winds which gradually decreased on Wednesday.
Thursday began mostly sunny but increasing clouds were seen in the afternoon. SW winds above treeline increased and become were very strong Thursday afternoon, with a gust above 100 mph at 6 PM recorded at the Cascade Express weather station at Mt. Hood Meadows. Â
Recent Observations
Several contacts were made with the Mt Hood Meadows patrol through the day Tuesday and they reported widespread natural and triggered wind and storm slabs especially near and above treeline. Avalanches were occurring even on relatively low angled terrain. Over 2 feet of new snow had accumulated by early Tuesday with more snow received through the day. Low visibility limited additional observations but by Tuesday afternoon large hard wind slabs were developing above treeline and several sympathetic avalanches were triggered. The recent relatively stable snowpack had quickly turned into very dangerous avalanche conditions.
By Wednesday conditions had improved and the Mt Hood Meadows patrol reported sunny but windy conditions with windward slopes getting scoured and local size-able wind slab building on lee slopes. The lower mountain was showing signs of spring with rollerballs and small triggered loose wet avalanches.
On Thursday Laura Green reported that a sun crust had formed on solar slopes. She passed along that several natural hard wind slab avalanches had occurred in White River Canyon above treeline on E-NE aspects with crown depths up to several feet. These hard slab wind avalanches likely occurred on Wednesday. Â
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: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
Likelihood: Likely
Expected Size: 1 - 1
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: All aspects.
Elevations: All elevations.
Likelihood: Likely
Expected Size: 1 - 1
Loose Wet
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. They generally move slowly, but can contain enough mass to cause significant damage to trees, cars or buildings. 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.
Travel when the snow surface is colder and stronger. Plan your trips to avoid crossing on or under very steep slopes in the afternoon. Move to colder, shadier slopes once the snow surface turns slushly. Avoid steep, sunlit slopes above terrain traps, cliffs areas and long sustained steep pitches.
Several loose wet avalanches, and lots of pinwheels and roller balls.
Loose wet avalanches occur where water is running through the snowpack, and release at or below the trigger point. Avoid terrain traps such as cliffs, gullies, or tree wells. Exit avalanche terrain when you see pinwheels, roller balls, a slushy surface, or during rain-on-snow events.
Elevations: Below Treeline.
Likelihood: Possible
Expected Size: 1 - 1