Avalanche Forecast
Regions: Mt Hood.
Little change in the avalanche danger is expected Monday with recent wind slabs primarily found on N-SE aspects and mainly above treeline. However be alert for wind slab on all terrain aspects due to shifting winds and cross-loading during the last storm. Small loose wet avalanches will be possible on steeper solar aspects Monday due to sunshine and rising freezing levels.
Detailed Forecast
Mt. Hood should squeeze out another fine January day with the bulk of the incoming moisture and precipitation directed further north on Monday. Sunshine should be interspersed with periods of high clouds and freezing levels should continue their recent upward trend.Â
Recent wind slabs at Mt Hood should be primarily on N-E aspects but be alert on all terrain aspects for firmer wind transported snow near and above treeline. The benign weather will continue to slowly allow these layers to stabilize. Remember that firmer wind transported snow is always your best sign of wind slab layers.
Small loose wet avalanches will be possible on steeper solar aspects Monday due to sunshine and rising freezing levels. Watch for pinwheeling of wet surface snow as an indicator that triggering shallow loose wet slides is possible.Â
Snowpack Discussion
Weather and Snowpack
A low pressure system tracked across Oregon Tuesday morning through Wednesday afternoon. Mt. Hood was stacking up the new snow Tuesday with 15-20 inches falling Monday night through Wednesday mid-day. Winds were generally light to moderate in this storm, but E winds increased mid-mountain Tuesday afternoon, then switched to SW Wednesday.
An upper ridge over the northeast Pacific Ocean has caused fair weather Thursday through Sunday over the Olympics and Cascades with mostly light winds and moderating temperatures.Â
Surface hoar and near surface faceting has been noted widely throughout the Cascade range in sun and wind sheltered locations below treeline. Sun crusts have formed on steeper solar aspects over the last few days. The best riding and skiing conditions have generally been reported in less wind and sun affected areas below treeline during this stretch of fair weather.
Recent Observations
On Wednesday, Meadows pro-patrol did not venture above about 6600 feet due to white-out conditions. Below this elevation, in the mostly below tree line band, sheltered slopes were maintaining right side up powder conditions that lacked any slab structure, providing excellent conditions.
On Thursday, the pro-patrol reported one natural 8 inch x 300 foot wide natural slab avalanche that occurred Wednesday on a south slope at 6500 ft. Otherwise on Thursday only pockets of 4-10 inch wind slab were released by explosives on N-NE slopes in the near and above treeline due to SW winds on Wednesday.
A couple reports for Mt Hood area available via the NWAC Observations page for Thursday. A skier on the north side of Mt Hood noted E and W wind effects and potential wind slab in the near and above treeline. Another skier on Pea Gravel Ridge noted limited, thin wind slab near the top of the Ridge but otherwise snow was right side up and cornice and ski tests gave no results.
NWAC pro-observer Laura Green was touring in the east fork of Hood River up to 6100 ft on Friday. She found the upper snowpack generally non-reactive in snowpack tests with good skiing conditions especially below treeline. Good surface hoar growth was noted up to 6100 ft.Â
We did receive one report of an 8-10" soft slab triggered below treeline on an easterly aspect that occurred Saturday. While we believe slab avalanches are unlikely below treeline, small avalanches remain possible in isolated areas.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: All aspects.
Elevations: Alpine.
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.
Aspects: South East, South, South West.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1 - 1