Avalanche Forecast
Regions: Mt Hood.
Intense snow and wind brought dangerous avalanche conditions and very large Wind Slabs avalanches to the Mt Hood area. Three feet of snow has accumulated since Friday. Avoid obvious wind drifts and deep pillows of snow on leeward and crossloaded slopes 35 degrees and steeper.
Detailed Forecast
Dangerous avalanche conditions will persist Monday following a strong storm passage Sunday. Snow showers should taper overnight Sunday and end by early Monday. Temperatures should cool with diminishing winds by Monday. Monday should be cool with light winds and partial clearing with a chance of a few light snow showers but little if any accumulation expected.Â
The strong storm Sunday produced widespread wind and storm slabs in the Mt Hood area. These large wind and storm slabs will take some extra time to heal and strengthen.
You will be able to trigger an avalanche Monday, especially in areas that received significant wind loaded snow, such as steep slopes below ridges, mainly facing North to Southeast. Any triggered avalanche could become very large as there is a significant amount of storm snow available to become involved in an avalanche.
Back country travelers should continue to travel with extra caution and best to travel in shallower angled terrain well away from avalanche paths or runout zones where avalanches release from above.Â
Snowpack Discussion
Older low density snow from last week has been loaded by back to back strong storms over the weekend with about 3 ft of new storm snow accumulating by Sunday evening!Â
Very strong winds and heavy snowfall intensities since late Friday have built large to very large wind slabs near and above treeline. Storm slabs have built over weaker lower density snow deposited late last week.Â
This snowpack structure is creating dangerous avalanche conditions in the Mt Hood area.Â
Avalanches releasing in the most recent storm snow may step down to older storm layers creating large avalanches.
The deepening storm snow now sits over a strong crust layer formed and buried on Saturday 2/17. This crust has been reported up to 6600 feet by professionals in the region.Â
One person was killed in an avalanche south of Snoqualmie Pass on Sunday. Our condolences go to the friends and family of the victim. If conditions allow, NWAC staff will visit the accident site.
Observations
By Sunday morning, MHM professional patrol reported "monumental" snow drifts! These conditions have only become larger by Monday.
MHM professional patrol on Saturday reported white out conditions above treeline with significant wind transport occurring. Below treeline the surface snow was forming unstable storm slabs. Still relatively shallow storm slab avalanches were releasing with explosives Saturday morning.Â
NWAC pro-observer Laura Green traveled in the Mt Hood backcountry Friday. Laura reported stable conditions prior to Friday’s incoming storm. She found a right-side-up snowpack with loose unconsolidated surface snow.
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 - 2
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.
Elevations: Treeline, Below Treeline.
Likelihood: Possible
Expected Size: 1 - 1