Avalanche Forecast
Regions: Mt Hood.
Watch for firmer wind transported snow and recent wind slabs on exposed lee slopes especially near and above treeline.
Detailed Forecast
Fair weather should be seen Tuesday with light winds and little change in temperatures.
These conditions should allow for continued gradual decrease in avalanche danger as recent wind and storm slabs further settle and further stabilize.Â
Recently formed wind slab should further stabilize on Tuesday. From the most recent report from Mt Hood Meadows wind slabs are most likely on NE-E aspects. Watch for recent wind effects near and below ridgelines and avoid steep slopes with obvious signs of recent wind loading.
Storm slabs should become more stubborn to trigger Tuesday. Head for lower angle slopes if you encounter denser snow over weaker storm snow.
Although we won't list it as avalanche problem watch for wet snow avalanches on steep solar aspects if the sun is out in the afternoon.
Snowpack Discussion
Weather and Snowpack
An arctic air mass was over the Northwest with fair, cold weather the 2nd week of January. 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 to determine if 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 about 1/17. Heavy rain was seen up to about 7000 feet at Mt. Hood. Three day precipitation totals through about Thursday were about 1.5 - 2 inches of water at the NWAC Timberline and Meadows 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.
Bands of showers moved across the Mt Hood area Saturday and Sunday depositing 7-8 inches more snow with further cooling and moderate winds.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 the 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 was reported below treeline.
By Saturday the pro-patrol at Meadows were seeing very limited results as much of the recent wind slab problem had begun settling. At elevations below the recent wind loading, storm snow lacked cohesion and was providing nice conditions.
On Monday the pro-patrol at Meadows reported only pockets of stubborn wind slab above treeline on EÂ slopes. This area had not been open or skied for 3 days so should be more representative of back country conditions.
Â
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: 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: Possible
Expected Size: 1 - 1