Avalanche Forecast
Regions: Mt Hood.
Heightened avalanche conditions are expected on specific terrain features, such as exposed lee slopes below ridges receiving wind transported snow. Evaluate the snow and terrain carefully: identify features of concern.
Detailed Forecast
A mostly dry but cloudy day is in store Friday with warming and increasing winds. A period of light rain and snow at rising freezing levels is expected again late Friday along with strong S-SW  ridgetop winds. Recent storm related danger will continue Friday, especially above treeline as strong southwest wind loads lee slopes where snow is available to transport. Areas of wind slabs will build on isolated lee slopes, facing generally N-E. Â
Heightened avalanche conditions on specific terrain features is expected. Evaluate snow and terrain carefully, especially in higher exposed terrain.
Non-avalanche hazard: Despite our seasonally, healthy snowpack, many creeks are open and difficult to cross due to the periodic warm temperatures and rain events. Â
Snowpack Discussion
Weather and Snowpack
Very mild weather a week ago allowed for the formation of a strong melt-freeze crust, especially thick on solar slopes in most areas by Friday. A weak front brought quite a bit of mostly rain to Mt Hood Friday night to Saturday morning.
A strong Pacific frontal system blew through the Cascades midday Sunday. Significant transport winds were from the W-SW and seen in the early afternoon post-frontal passage with gusts in the 40s or 50s near treeline with gusts recorded above 100 mph at the Mt. Hood Meadows Cascade Express station (7300 ft)!Â
A warm front quickly dropped up to 6 inches of new snow early Tuesday morning at NWAC Mt. Hood stations before changing to rain. After a late morning lull, precipitation rates increased again in the afternoon as the cold front approached and snow levels began lowering. Not to be outdone by Sunday's system, gusts over 150 mph were recorded at the Cascade Express station (7300') Tuesday afternoon!Â
Wednesday was a transition day between storms with some early sunshine and mild temperatures and diminishing winds.Â
The mid and lower snow pack along the west slopes should be a stable mix of crusts and layers of moist and rounded snow crystals.
Recent Observations
Observations were limited Tuesday, but rain runnels were noted up to 6800 feet. At 6200', the top 30 cm of snow was wet. Mt. Hood Meadows pro-patrol noted 6-8" loose wet avalanches sensitive to ski cuts on steeper east aspects above treeline.Â
The aftermath of the extreme wind event Tuesday was seen on Wednesday, with any exposed terrain stripped of recent snow, exposing a strong crust. The wind deposits were inconsistent and did not yield much in the way of avalanches, despite a healthy dose of bombs in the Mt Hood Meadows area.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.
Elevations: Alpine, Treeline.
Likelihood: Possible
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: Treeline, Below Treeline.
Likelihood: Possible
Expected Size: 1 - 1