Avalanche Forecast

Brief high pressure should rebuild along the PNW coastal areas Tuesday. This should maintain partly to mostly cloudy skies, light winds and continued cool temperatures. 

This weather should allow for continued gradual settlement of any recent storm layers or wind slabs in higher exposed terrain. However, cool temperatures will help slow this process and may preserve wind slabs in higher terrain.

Watch for wind stiffened snow on a variety of aspects, including non-traditional aspects from recent northerly winds

There is a lot of deep soft snow out there from the past week. Unconsolidated snow, particularly around small trees, can present a non-avalanche, snow immersion hazard. Keep visual and verbal communication with your travel partners when traveling in treed terrain.

Also despite all this new snow, early season hazards still exist at some lower elevation locales and especially around creek beds that are not filled in.

A weak disturbance moved across the Cascades Christmas Eve depositing 2-6 inches of new snow, with generally light winds recorded. 

Moderate to strong E-SE  crest level winds have been seen late Saturday and Sunday with light to moderate E winds in the lower Cascade Passes.

About 1-11 inches of light snow fell across the west slopes of the Washington Cascades and Passes in the 24 hours ending Saturday morning with the most in the southwest Cascades. This added to the very impressive 1-4 feet that fell across the same area early in the week. Recent deep storm snow has been settling and stabilizing over the last several days. Numerous field observations from throughout the west slopes of the Washington Cascades indicate that storm layers continue to gradually stabilize.

Moderate to strong SW-W crest level winds transported snow in exposed terrain Tuesday to Thursday forming wind slabs on a variety of aspects.

In general, 2.5 to 3.5 feet of increasingly firm snow now sits above the 12/15 layer. Observations have not demonstrated consistent layers of concern within the upper snowpack. 

Observations

North

On Saturday, a skier on Mt Herman, reported no signs of instability via the NWAC Observations page.

Last Wednesday, the Mt Baker Pro Patrol observed significant wind transport on exposed terrain features mainly above treeline as ridge top winds increased. There was a 2 foot human triggered slab avalanche that propagated about 45-75 feet wide near ridgeline.

Central 

On Christmas Day, the Alpental Pro Patrol indicated the 24 hr storm snow of about 6 inches showed little to no wind affect. Ski cuts produced only shallow loose-dry slides confined to steep, isolated features and did not entrain significant snow or travel far in the paths. 

Triggered wind slab, with one party caught, as reported on the NWAC Obs page Sunday indicating cautious travel when transitioning to wind affected terrain is wise!

A skier on Humpback Mountain via the NWAC Observations page for Saturday reported getting caught by a small 2 foot wind slab on a W facing slope near the summit. No serious injuries were reported. Note that areas west of Snoqualmie typically have stronger winds during periods of offshore flow.

NWAC pro observer Jeremy Allyn was in the Chair Peak - Mt Roosevelt area on Saturday and reported windy conditions on the shoulder of Chair Peak. His party triggered 2 small wind slabs on the north slope of Chair Peak at about 4800 feet. Storm layers are healing slowly due to cold temperatures.

The Stevens pro patrol on Saturday found moderate CT result in storm layers, with hard or no results on the 12/15 layer down 85-90 cm in north slope pits at 4800 and 5800 feet. No wind slab was observed.

NWAC forecaster Robert Hahn was on Jove Peak on Friday and found deep trail breaking, small subtle wind slab on the ridge, storm slab no longer an issue, no signs of instability and good skiing.

A public observation from Stevens Pass Thursday reported triggering very small isolated wind slabs in wind loaded terrain. The party also noted a mostly right-side-up snowpack that was gaining strength.

South

A nice report via the NWAC Observations page from the Tatoosh on Saturday reported several triggered D1-1.5 loose dry avalanches on various steep slopes.

Professional observations from the Crystal Mountain backcountry Wednesday and Thursday are consistently demonstrating a well bonded and strengthening snowpack. Many newly formed cornices along the ridges failed easily under a travelers weight.