Avalanche Forecast
Regions: Mt Hood.
A mixed bag of conditions is possible in the Olympics and Cascades on Sunday. Possible lingering loose wet avalanche conditions have been emphasized Sunday morning at Mt Hood. Old wind slab may linger on specific steep terrain features.
Detailed Forecast
A weakening front will move over the upper ridge and cause increasing alpine winds on Sunday. At Mt Hood it should still be mild or rather warm through the morning hours. Then light to moderate rain or snow should spread to the Olympics and northwest Cascades with a cooling trend beginning in all areas by Sunday afternoon.
At Mt Hood the main avalanche problem should be possible lingering loose wet avalanche conditions through Sunday morning. Increasing winds should help keep surface snow firmer and limit loose wet avalanche activity above treeline. Watch for natural releases of any size and wet surface snow deeper than a few inches.
Old wind slab may also linger mainly on specific, steep northwest to southeast terrain features above treeline.
Snowpack Discussion
Weather and Snowpack
An arctic air mass settled over the Northwest with fair, cold weather from the New Year the second week of January.
An atmospheric river arrived Tuesday 1/17 with heavy rain up to about 7000 feet on Mt. Hood during this stretch. Three day precipitation totals through Thursday 1/19 were about 1.5 - 2 inches of water at the NWAC Timberline and Meadows stations.Â
From last Thursday 1/19 through Sunday, 1/22, generally 15-20 inches of snow accumulated at NWAC Mt Hood stations.
Fair weather with light winds and cool temperatures occurred Monday and Tuesday. A period of shifting and gusty winds Tuesday night helped redistribute recent snowfall to a variety of aspects by Wednesday morning. Light showers Tuesday and Wednesday produced about 1 to 4 inches of new snow.
A large upper ridge and warm air mass built over the Northwest Thursday to Saturday. By Saturday temperatures have reached the 40's at and at higher elevations especially along the west slopes.
Recent Observations
On Monday, the pro-patrol at Meadows reported only pockets of stubborn wind slab above treeline on easterly aspects. This area had not been open or skied for 3 days and more closely represented true backcountry conditions.
NWAC pro-observer, Matt Schonwald was at Timberline on Monday and on the southeast slopes at about 6600 feet, finding right side up, increasingly resistant, settled snow with a good bond to the 1/17 crust. Shallow wind slabs showed little tendency to propagate via ski tests.
The Mt Hood Meadows pro-patrol reported isolated areas of shallow and soft wind slab up to 12 inches deep on a variety of aspects above treeline due to shifting winds Tuesday night.
NWAC pro-observer Laura Green was at Mt Hood Meadows Thursday and Friday and reported dripping trees and roller balls due to loose wet snow on solar slopes. She reported a general lack of weak layers and ice layers in the snow pack on most aspects but good skiing still to be found on some slopes depending on aspect, elevation and timing.
A worthwhile conditions report for the Reid Glacier for Friday is also available via the NWAC Observations page.
Avalanche Problems
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.
Aspects: South East, South, South West.
Elevations: All elevations.
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, North West.
Elevations: Alpine, Treeline.
Likelihood: Unlikely
Expected Size: 1 - 1