Avalanche Forecast
Regions: Mt Hood.
New shallow wind and storm slab layers seem possible by later Friday mainly in the near and above treeline at Mt Hood due to winds, new snow and a warming trend.
Detailed Forecast
A frontal system will cross the Northwest on Friday. This will cause increasing southwest to west alpine winds, increasing rain or snow and a rise in snow levels.
Perhaps about 5-7 inches of snow seems likely at Mt Hood mainly in the near and above treeline band by later Friday with a warming trend.
This weather should build new upside down wind slab on lee slopes which should be mainly southeast to northwest slopes near and above treeline by later Friday. Watch for firm wind transported or hollow sounding snow.
New shallow storm slab is possible in areas that see rapid accumulations of new snow by later Friday. The warming trend will also aid in the development of new upside down storm slab.
Small human triggered avalanches in many areas in the near and above treeline seems possible by later Friday at Mt Hood due to the alpine winds, new snow and the warming trend.
In the lower part of the below treeline band there is still insufficient snow for avalanches but watch for early season hazards such as terrain traps, rocks and creeks.
Snowpack Discussion
Weather stations on Mt. Hood picked up 11Â and 15 inches of new snow at Timberline and Mt. Hood Meadows respectively Monday morning. Another 7 to 9 inches fell during heavy showers through Monday evening. West to northwest winds remained moderate on Monday helping to transport new snow to lee easterly aspects.Â
The Mt. Hood Meadows pro patrol found sensitive, but soft 6-12 inch storm slabs on most aspects Monday morning failing within the new storm snow. Â Wind slabs averaged 18 inches on north aspects above treeline with a crust for a bed surface that formed during a warm-up last Friday.Â
On Tuesday the Mt Hood Meadows pro patrol found shallow storm slabs near and below treeline generally unresponsive to ski cuts and explosives. Â However, evidence of two larger natural wind slab avalanches was observed in White River Canyon, on east to southeast aspects, both with start zones around 7000 feet. One stepped down to deeper layers.
Another front passed over the Northwest on Wednesday. NWAC stations at Mt Hood had winds generally in the teen to 20Â mph range with variable, very strong gusts. New snow on Thursday morning was around 10Â inches at NWAC stations at Mt Hood.
A bit of a break has been seen on Thursday with snow showers tapering at Mt Hood.
NWAC pro observer Laura Green was at Mt Hood Meadows ski area on Thursday and reported significant wind transport but with minor small wind slab via ski area control results. But wind slab will be deeper in areas not visited by the ski area control crews.
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: 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: Alpine, Treeline.
Likelihood: Possible
Expected Size: 1 - 1