Avalanche Forecast
Issued: Apr 1st, 2018 12:23PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Storm Slabs.
NWAC,
Northwest Avalanche Center
New snowfall combined with sustained moderate W-NW winds will create dangerous avalanche conditions Monday. Expect to find fresh Wind Slabs on lee slopes near and above treeline. Moderate winds may form Wind Slabs further downslope than usual. You may encounter Storm Slab or Loose Dry avalanches in steep less wind-affected terrain.
Summary
Detailed Forecast
Significant new snowfall should accumulate through Monday morning. New snowfall combined with sustained moderate W-NW winds will create dangerous avalanche conditions Monday.
Expect to find fresh Wind Slabs on lee slopes near and above treeline Monday, especially on NW-N-E-SE aspects. Moderate winds may form Wind Slabs further downslope than usual. Use visual clues such as snow drifts, cornices, wind textured snow, and firm snow surface conditions that produce cracks to identify and avoid wind loaded areas. Avoid triggering these avalanches by steering around steep roll-overs, unsupported features, and obvious start zones where you suspect Wind Slabs.
Near and below treeline the new snow is falling on slick or refreezing surface crusts. You may be able to trigger a Storm Slab on slopes over 35 degrees where cohesive new snow slides easily on the old snow surface.
Loose Dry avalanches may release during sunbreaks or can be triggered in steep terrain, running fast above the most recent crust. Recognize exposure to terrain traps where even a small Loose Dry avalanche would have unintended consequences.
Snowpack Discussion
Up to 4 inches of snow accumulated in the Mt. Hood area by 5 pm Sunday with temperatures slowly dropping in the afternoon and moderate W-SW winds reported near and above treeline.
Despite light winds and temperatures in the 30s to lower 40s near and below treeline Saturday, overcast skies for much of the day kept surface snow firm and limited new Wet Loose avalanche activity.
There are currently no significant layers of concern in the mid or lower snowpack.
Observations
On Saturday, Mt. Hood Meadows pro-patrol reported high overcast skies limiting the softening of surface snow on all aspects. No new avalanches were observed.
On Friday, professional reports indicated very little Wet Loose avalanche activity and that rock outcrops had already shed most of their snow.
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
Expected Size
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
Expected Size
Valid until: Apr 2nd, 2018 12:23PM
