Avalanche Forecast
Regions: Mt Hood.
Avalanche problems should be found in new snow layers on Monday.
Detailed Forecast
A snowy system is headed our way Sunday afternoon to Monday. This will cause some strong alpine winds and should be a good snow producer especially for the Cascade west slopes and Mt Hood area.
Slowly decreasing northwest flow should carry a cool, slightly unstable air mass and snow showers to the Olympics and Cascades on Monday. The west slopes will continue to be favored and convergence is likely in the central Cascades. Extra snow showers should also be seen at Mt Hood on Monday.
Any avalanche problems should be found in new snow layers. Watch for signs of firmer wind transported snow that indicate wind slab. Storm slab is most likely in areas that rapidly accumulate more than several inches of new snow.
A cooling trend should help give favorable right side up new snow profiles in sheltered areas where new snow does not accumulate too rapidly or too deeply.
In most areas in the below treeline band there is not enough snow yet for avalanches. Any avalanche problems would be only in the upper part of this band.
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Snowpack Discussion
A weakening front with a lot moisture flowing south to north along the frontal boundary moved slowly into the Northwest with a warming trend late Friday and Saturday. There a brief break by Sunday morning with a cooling trend but the next front is beginning to arrive on Sunday afternoon. Fairly light amounts of new snow were seen at Mt Hood on Saturday morning and Sunday morning. There is about 14 and 20 inches of total snow at the NWAC stations at Mt Hood Meadows and Timberline Sunday morning.
A report for Barrett Spur on the north side of the mountain was received via the NWAC Observations tab for Saturday. Wind transport was seen in the above treeline band with a low quality shear test at 50 cm down in the snowpack.
The Mt Hood Meadows pro patrol reported that at 6600 feet on Sunday morning areas of snow were scoured to a crust from Friday with only isolated pockets of very shallow wind slab.
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