Avalanche Forecast

A weakening cold front should bring a brief period of light to occasionally moderate rain and snow Monday night, with the rain/snow line into the above treeline terrain. Further cooling should follow the front and rain/snow showers will re-develop behind the front during the day Tuesday and light to moderate SW crest-level winds will transport the new snow as it accumulates. The old snow surfaces are expected to begin to refreeze at higher elevations as temperatures cool. New snowfall on Tuesday is anticipated to bond well to the refreezing snow surfaces.

Watch for the development of shallow wind slabs, particularly on NW through SE aspects above treeline. The Cascade West-North zone is expected to receive the most new snow (approximately 5") and in this zone, wind slabs may work their way into the near treeline zone, so monitor new snow and wind transport diligently throughout the day and avoid wind-loaded slopes.

Note that while it's not listed as a problem here, wet snow exists in the upper snowpack and before a crust has fully formed at lower elevations it may still be possible to trigger a loose wet slide during the morning hours. Where boot penetration is deep, adjust your plans accordingly.

Note that a variety of snow conditions may be encountered on Tuesday, including breakable crusts, wet snow, new snow over refreezing surfaces, etc.

Three days of very warm (is this January??) high pressure created melt-freeze conditions on all aspects with a very shallow refreeze or non-existent refreeze in many areas Sunday night. The recent warm conditions are working with a snowpack that received rain in many areas up to treeline or above last Thursday night into Friday and 2 or more feet of cold snow above the rain/snow line. Winds redistributed the snow during the recent storms, depositing snow onto a variety of aspects. The warm temperatures are helping wind slabs to heal more rapidly and is also contributing to significant settlement of the recent storm snow with up to 15" of settlement observed around Stevens Pass. The snowpack climatology is slightly below normal in most areas as of Monday, January 15th.

The graphs below nicely illustrate the transition from the most recent storm cycle to high freezing levels seen over the holiday weekend. Temperature inversions with locally cooler temperatures occurred in the passes due to easterly flow.  Moderate SE winds cooled the snow surface in a few areas, such as Crystal mountain on Sunday and Monday. It's worth noting that all stations near and west of the Crest have experienced significant time above freezing since the most recent snowfall.

The storm snow from late last week sits on a thin crust (Jan. 9) Found in the near treeline elevation band in most areas. A more supportable and thicker crust (Jan. 5) from rain or freezing rain is easily identifiable in the upper snowpack.

Below the 1/5 crust, observations continue to indicate a strong snowpack with no notable layers of concern.

Observations

North

Large natural and skier-triggered loose wet avalanches were reported on Sunday in the Twin Lakes area by Baker Pro Patrol and Hidden Lake Peak area via our public observations page.

Mt Baker Ski Patrol reported rain at 4800 feet in the ski area Friday. Recent loose wet avalanche activity was observed below treeline in the surrounding terrain. Low visibility limited observations in the near and above treeline terrain outside the ski area.

Central

Snoqualmie Pass WSDOT and Alpental Pro Patrol Reported rain to 5000 feet Friday with ice pellets above. Several natural loose wet avalanches were observed from Thursday night, some running 1000 feet. No new avalanches were observed on Saturday.

An avalanche professional in the Alpental valley on Saturday observed wet surface snow down 4 inches and moist snow all the way to the 1/5 crust below treeline. He reported very difficult travel conditions due to the wet heavy snow. 

South

NWAC professional observer Jeremy Allyn traveled in the Crystal Mountain backcountry Friday. He observed rain to 5400 feet. In near treeline areas observations showed storm snow weaknesses gaining strength.