Avalanche Forecast

A frontal system should take aim mainly at the north Cascades Saturday, with precipitation becoming heavy around mid-day.  A slow warming trend should ensue for the latter half of the day, and winds above treeline should become strong by the afternoon.  For the north Cascades zone, we are assuming that most of the recent storm snow instabilities have settled out and will turn our attention to new storm snow instabilities.

Storm and wind slabs will quickly develop in the afternoon as the storm intensifies. Stay off wind loaded N-SE aspects later in the day and be prepared to curtail your plans if conditions deteriorate faster than expected.    

Human triggered natural slab avalanches are likely by the late afternoon, especially near and above treeline and on lee slopes.  

Early season hazards exist for much of the below tree-line band throughout the Northwest, so ski and ride with caution. 

Note: The snowpack discussion is for the entire west slopes of the Cascades, but the avalanche danger forecast varies by zone.  

 

We had a wild and wet month of November, with 12- 25 inches of water at west side NWAC stations only amounting to a 1 meter (~3 ft) snowpack in the north Cascades above 4000 ft and above 6000 feet elsewhere. Strong high pressure led to steep temperature inversions and brought very cold air through the Cascade Passes over Thanksgiving weekend. The weather pattern has become more active for the first few days of December with a few inches of new snow over the west slopes paired with moderating temperatures in the Passes. 

Avalanche and snowpack observations: Recent activity along the west slopes away from the Cascade Passes has been confined to new storm snow. New NWAC pro-observer Lee Lazzara noted a natural cycle of loose wet avalanches on Wednesday as temperatures warmed. This natural cycle likely extended to higher elevations in the north Cascades on Thursday as rain pushed above 5000'.  Mt. Baker and Crystal patrols reported small avalanches involving new storm snow during control work Fri AM.   

The west slopes do not have a uniform maritime snowpack! Due to cold temperatures and clear skies near the end of November, buried surface hoar can be found in the Stevens Pass area.  NWAC pro-observer Dallas Glass found this layer around 5000' on Skyline on E-NE aspects around 45 cm down. Faceting may also be found solar aspects around a buried sun crust.  Stevens pass pro patrol reported a 12-14" (30-35 cm) natural persistent slab avalanche in closed Corona Bowl of the ski area Friday on a N-NW aspect.  Professionals also reported shooting cracks and whumpfing in the area as temperatures warmed and the slab above the PWL became cohesive.

We still have many gaps in our observation network as it's early season, so make your own observations and use them in co-junction to our regional avalanche forecast. Thanks for reading the first NWAC avalanche forecast for 2015-16 season, stay safe and have fun!