Avalanche Forecast
Issued: Mar 15th, 2018 10:55AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs.
NWAC,
Northwest Avalanche Center
Avalanche hazard will be limited Friday by cool cloudy weather on Mt Hood. You are most likely to trigger a wind slab on lee slopes at higher elevations where older deeper wind slabs linger and new shallow winds slabs may form. Stay off of any slope above treeline where you think wind loading has occurred.
Summary
Detailed Forecast
Stay off of steep wind loaded slopes at higher elevations Friday where you may trigger a wind slab. Use visual clues such as blowing snow, fresh cornices, and snow drifts to identify and avoid wind loaded slopes. You will most likely to trigger a wind slab on convex roll overs, unsupported slopes, or on cross-loaded features.
In other locations, general safe avalanche conditions will exist. Cloudy skies, cold temperatures, and snow showers will limit the avalanche hazard in the Mt Hood area. Keep an eye out for signs of unstable snow such as blowing snow, shooting cracks, or sunshine affecting fresh snow. If you encounter these conditions, avoid areas where avalanches can start.
Snowpack Discussion
A few inches of new snow have accumulated in the cool showery pattern seen since Wednesday. Above treeline isolated wind slabs developed with moderate southerly winds. This recent snow sits atop a new melt-freeze crust formed earlier in the week.
Several melt-freeze cycles Saturday through Monday this past week consolidated and strengthened the snowpack.
While we are tracking several layers deeper in the snowpack, there are currently no significant layers of concern.
Observations
On Wednesday, Mt. Hood Meadows Pro-Patrol reported shallow wind slabs less than 1 ft triggered by explosives on N-NE aspects near and above treeline.
Mt. Hood Meadows Pro-Patrol reported warm and wet snow conditions Sunday and Monday on steep sunny slopes.
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.
Likelihood
Expected Size
Valid until: Mar 16th, 2018 10:55AM
