Avalanche Forecast
Issued: Jan 9th, 2018 8:32PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs.
NWAC,
Northwest Avalanche Center
Building and reactive wind slabs may be found on a variety of aspects near and above treeline. Refreezing moist or wet snow below treeline will maintain a low avalanche danger in most areas. Watch for changing conditions Wednesday if the incoming storm arrives sooner than forecast and be prepared to alter plans accordingly.
Summary
Detailed Forecast
A cooling trend continues with scattered light showers overnight Tuesday and early Wednesday with light to moderate winds.
The shallow recent snow since Sunday will be available for wind transport and will support wind slabs forming near and above treeline on a variety of exposed slopes.
The next strong storm is forecast to arrive Wednesday night, however if the storm arrives earlier than forecast expect increasing danger late Wednesday. Watch for changing weather conditions through the day Wednesday and be prepared to alter plans accordingly.
Below treeline, expect strengthening and refreezing of Tuesday's moist to wet surface snow. Only shallow new snow is expected above a very strong overall snowpack in most below treeline areas.
Early season hazards still exist. Many creek beds have still not filled in for the winter.
Snowpack Discussion
Recent mild conditions on Mt Hood have prevented much new snow below treeline with shallow new snow accumulating near and above treeline by Tuesday.
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
Pro patrol at Mt Hood Meadows Tuesday, reported fresh wind slabs forming up to 10 inches in exposed terrain near treeline. White out conditions prevented observations above treeline.
On Sunday, the Mt. Hood Meadows patrol reported that the surface crust was softening at all elevations in their area.
NWAC pro-observer Laura Green was in the Bennett Pass area of the White River drainage on Saturday up to 6100 ft. Laura found challenging travel conditions with a surface crust of variable strength and no notable layers of concern in the upper snowpack. No new avalanche activity was observed.
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, South East, South.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 10th, 2018 8:32PM
