Avalanche Forecast
Regions: Mt Hood.
The greatest avalanche problem should be wind slab on lee slopes near and above treeline mainly N-SE facing slopes. Watch for signs of cracking or firmer wind transported snow.
Detailed Forecast
One more day of light winds and cool temperatures should be seen at Mt Hood on Tuesday.
This weather should bring a further gradually decreasing avalanche danger.
The greatest avalanche problem should be wind slab on lee slopes near and above treeline mainly N-SE facing slopes. Watch for signs of cracking or firmer wind transported snow.
Also watch for lingering storm slab in areas that had rapidly accumulating snowfall.
Although this won't be listed as a problem watch for triggered loose dry avalanches if you venture onto very steep slopes.
Loose wet avalanches also won't be listed as a problem but if solar effects or sun are significant watch for wet snow deeper than a few inches and pinwheels or small natural loose wet avalanches that usually precede larger loose wet avalanches on solar slopes.
Avoid ridges where cornices may be present and slopes below cornices. Cornices can always be sensitive to human triggers.
Continue to evaluate snow and terrain carefully on Monday.
Snowpack Discussion
Weather and Snowpack
Warm wet weather will have caused increasing wet snow conditions at Mt Hood Wednesday-Thursday.
A strong occluded front with strong winds crossed the Northwest on Friday. NWAC stations at Mt Hood had about a foot of new snow by Saturday morning. About another 6-8 inches followed at the tail by Sunday morning. Cool weather has been seen Sunday and Monday.
Some areas have reported a strong bond of the new snow to the crust and some a poor bond depending on if the new snow arrived after cooling began. Sensitive storm layers have also been reported within the storm snow which will take a bit of time to gradually stabilize.
Recent Observations
Decreasing avalanche activity was reported over the weekend. Here are summaries of some of the latest reports.
NWAC pro-observer Laura Green in the Clark-Mitchell-Heather Canyon areas reported building wind slab and building cornices on Friday.
A report via the NWAC Observations page for Pea Gravel Ridge on Saturday reported building 4-6 inch wind slab on lee slopes near ridges. Storm layers and storm slab were also noted.
On Sunday the Mt Hood Meadows patrol reported limited 4-6 inch wind slab on lee slopes in the above tree line, lower than usual below ridges, which would be small and difficult for a skier to trigger.
A report on Turns All Year for Sunday in Newton Canyon had gradually harder compression tests with depth in right side up storm snow with no signs of propagation.
The Mount Hood Meadows pro-patrol today reported minor wind transport in the above treeline giving isolated, small pockets of 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.
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