Avalanche Forecast
Issued: Jan 1st, 2020 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
Continued winds and new snow will build fresh wind slabs Wednesday night. Avoid wind loaded lee slopes and carefully evaluate the bond between new and old snow.
Summary
Discussion
The New Year’s Eve storm did not produce as much snow as expected. Rain and mixed precipitation extended to near treeline in many locations before transitioning to snow Wednesday. Reports suggest that the new snow is bonding well to the wet surface. However, the rain event did not fully saturate snow pack and weak layers in the upper snow pack may still be intact.
The rain did not reach these facets, about 6 inches below the surface of the snow. Crystal backcountry ~5500’ Photo: Dallas Glass
Snowpack Discussion
New Regional Synopsis coming soon. We update the Regional Synopsis every Thursday at 6 pm.
Problems
Wind Slabs
Strong and gusty winds have built fresh wind slabs which will continue to grow Wednesday night. With the strength and gusty nature of the recent winds, you may find wind slabs not only near ridge crests but also mid-slope. As winds calm down Thursday, new snow may hide visual clues of wind loading. Avoid wind loaded start zones and unsupported slopes. Evaluate the bond between new and old snow.
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
Valid until: Jan 2nd, 2020 10:00AM
