Avalanche Forecast
Regions: Mt Hood.
Backcountry travel in avalanche terrain near and above treeline at Mt. Hood is not recommended on Sunday. Careful snowpack evaluation, cautious route finding and conservative decision-making will be essential below treeline.
Detailed Forecast
Another front will bring more moderate rain and snow to Mt. Hood Sunday, beginning in the early morning and turning to moderate showers in the early afternoon.Â
This weather will generally cause upside down snow layers of increasing density near the surface and snow with rain likely below treeline in the morning. Up to about a foot of upside down snow should be seen by late Sunday afternoon.
New wind slab will continue to build mainly on lee north to east slopes near and above treeline. As the same lee aspects continue to load Sunday, very large avalanches will become possible.Â
New storm slab due to the warming trend is also very likely on varied aspects where winds are lighter and snow rapidly accumulates to deeper than a few inches Avalanches releasing in near surface layers on Sunday may entrain previous snow producing large avalanches.
Small loose wet avalanche will again be likely in areas that see initial snow turn to rain Sunday, mainly on steeper slopes below treeline.Â
Snowpack Discussion
The latest period of snowfall has been from about January 12-16th with up to about 2 feet at Mt Hood NWAC stations and fluctuating snow levels over this period.
A very active day on avalanche control was seen at Mt Hood Meadows Friday. The pro patrol reported explosively triggered widespread 1-4 foot slab avalanches on north to east slopes above treeline releasing on a crust from last weekend. Ski cuts were deemed to be too dangerous to undertake along with shooting cracks and some remote triggering by snow cats. Below treeline had storm slab and loose dry avalanches that were easy to trigger and running a more recent crust from about 2 days ago.
On Saturday, rain moved up to at least 6000 feet by late morning with snow levels lowering by mid-afternoon. Visibility was limited, but Meadows pro-patrol found 8-12" wet slabs very sensitive to ski cuts on steeper slopes below treeline. Steady winds continued to load lee aspects near and above treeline Saturday. 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: Very Likely
Expected Size: 1 - 2
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: Very 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: Very Likely
Expected Size: 1 - 1