Avalanche Forecast
Regions: Mt Hood.
Allow recent and shallow storm and wind slab time to stabilize on Saturday. Wind slabs are most likely on easterly aspects above treeline but will be listed on all aspects due to variable loading patterns during the last few days.
Detailed Forecast
Light to occasionally moderate snow showers should taper off Friday night before increasing again Saturday afternoon. Alpine winds may increase quickly Saturday afternoon out of the SW. Â
Allow recent and shallow storm and wind slab time to stabilize on Saturday. Wind slabs are most likely on easterly aspects above treeline but will be listed on all aspects due to variable loading patterns during the last few days. Look for recent wind effects near and below ridgelines and treat wind loaded slopes with caution.
Watch for shallow storm slabs on all aspects and in all elevation bands Saturday if sensitive storm layers form during heavier showers either Friday night or Saturday afternoon. Â
Snowpack Discussion
Weather and Snowpack
An arctic air mass was over the Northwest with fair, cold weather last week. Surface hoar and near surface faceted crystals formed in wind and sun sheltered areas during this period. Observations over the next few days should help determine to what extent any of these weak persistent grain types might have survived the atmospheric river event and remain relevant to the forecast moving forward.
An atmospheric river moved over the Northwest Tuesday and Wednesday. Heavy rain was seen up to about 7000 feet at Mt. Hood. 3 day precipitation totals through noon Thursday were about 1.5 - 2 inches of water at the Meadows and Timberline stations. Light snow showers and cooler temperatures were seen Thursday. A frontal band rotating up from the south dropped about 6 inches of snow at Meadows and Timberline through 6 pm Friday with steady snow levels seen during the day. Â
Recent Observations
The Mt Hood Meadows pro-patrol on Wednesday reported that rain penetrated about 10 inches into the snow with no results during avalanche control using explosives. Visibility was low on Wednesday and it could not be determined if there had been any natural avalanches on the upper mountain.
Visibility remained poor on Thursday but Meadows pro-patrol reported wind slabs releasing on NE aspects well above treeline control work with explosives. Wind slabs became less reactive near tree-line and no avalanche activity or layers or concern were reported below treeline. 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, Treeline.
Likelihood: Possible
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: Possible
Expected Size: 1 - 1