Avalanche Forecast
Regions: Mt Hood.
A consolidating and stabilizing trend will continue on Saturday. Remember to discuss plans and maintain visual contact with your partners.
Detailed Forecast
An upper ridge will shift over the Northwest on Saturday. This should cause light winds and fair weather on Saturday with freezing levels staying low in the Olympics and Cascades. Some high clouds should be seen by Saturday afternoon from a weak system that will approach Saturday night.
This weather will bring further consolidating and further stabilizing on Saturday. Cool temperatures may somewhat slow the stabilizing but the avalanche danger will be less than the previous few days.
Recent wind slab will be most likely to linger on north to east slopes in the above tree line. Wind and storm slab avalanches should stay within recent storm layers but could still move fast. Test for inverted strong over weak storm snow and give cornices a wide margin.
Beware of loose dry avalanches in steep non-wind affected terrain that could have unintended consequences such as knocking you off your feet and into a terrain trap.
Remember to discuss plans and maintain visual contact with your partners. Recent unconsolidated storm snow is very deep in many places with possible very large tree wells. There have been snow immersion fatalities in tree wells already this season at Snoqualmie and in Canada.
Snowpack Discussion
We have had about a week of heavy snow and cool temperatures in the Olympics and Cascades. NWAC sites at Mt Hood have had about 6-7 FEET of snowfall during this time!
Recent pro back country or pro patrol observations indicate extensive avalanches but confined to recent storm snow.
NWAC pro observer Laura Green was touring Wednesday in remote parts of the Mt Hood Meadows ski area and reported widespread, sensitive storm slab of 1-2 feet on north to east slopes in the 4500-6000 range.
Laura was out again on Thursday in Heather Canyon and noted that settlement, cold temperatures and declining winds were aiding in increasing stability and awesome skiing. Tests still indicated storm layers at 15-30 cm with sensitive remotely triggered wind slab seen on a north-northeast slope at 7000 feet.
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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: 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
Loose Dry
Release of dry unconsolidated snow. These avalanches typically occur within layers of soft snow near the surface of the snowpack. Loose Dry avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs. Loose Dry avalanches can trigger slab avalanches that break into deeper snow layers.
Loose Dry avalanches are usually relatively harmless to people. They can be hazardous if you are caught and carried into or over a terrain trap (e.g. gully, rocks, dense timber, cliff, crevasse) or down a long slope. Avoid traveling in or above terrain traps when Loose Dry avalanches are likely.
Loose Dry avalanche with the characteristic point initiation and fan shape.
Loose dry avalanches exist throughout the terrain, release at or below the trigger point, and can run in densely-treed areas. Avoid very steep slopes and terrain traps such as cliffs, gullies, or tree wells.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible
Expected Size: 1 - 1