Avalanche Forecast
Issued: Jan 5th, 2018 10:00AM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs.
NWAC,
Northwest Avalanche Center
Light snow and wind above treeline may develop small wind slabs overnight Friday and early Saturday. Monitor changing snow surface conditions throughout the day and be prepared to change your travel based on current conditions.
Summary
Detailed Forecast
Cooling overnight Friday with light rain showers changing to light snow showers. Showers should end by midday Saturday with further cooling and light winds.
The moist to wet snow surface will begin forming a new crust with only light amounts of fresh snow expected above. This should not lead to an overall increase in danger, especially at near and below treeline elevations.
Light snowfall and higher winds may occur at the upper elevations in the above treeline band. As snow begins to accumulate Friday night and early Saturday, keep watch for developing wind slabs on northerly to easterly facing slopes, mainly if greater new snow is received than forecast.
Early season hazards still exist. Many creek beds have still not filled in for the winter.
Snowpack Discussion
Light to moderate rain Thursday night and Friday began to soften surface crusts on most slopes.
Rain has fallen on a variety of snow surfaces, including wind scoured snow, crusts, and likely stubborn to unreactive wind slabs.
Several rain and freezing rain crusts are sandwiched in the upper snowpack depending on elevation. Current observations do not suggest these layers to be reactive.
Observations
Mt Hood Meadows Ski Patrol reported a melt-freeze crust at the surface Thursday prior to the precipitation event.
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, West, North West.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Jan 6th, 2018 10:00AM
