Avalanche Forecast

Previously moderate east winds should have diminished by Wednesday under mostly clear skies and gradually warming temperatures. When traveling into the near and above treeline zones, be prepared for recent wind slab formation on more southerly and westerly aspects. Older wind slab on more westerly aspects may still be sensitive in certain areas. Treat wind loaded slopes with caution, it is difficult to determine how sensitive they are with snowpack tests.

 

A storm system moved through the Northwest on Saturday and Saturday night delivering some much needed snowfall. West winds changed to northwest, with moderate to heavy snow west of the crest and a cooling trend. A convergence zone contributed to snowfall in the central Cascades on Sunday. NWAC sites west of the crest picked up about 12-20 inches of storm snow over the weekend except lower amounts at Snoqualmie Pass due to initially very wet snowfall. 

Professional observers west of the crest reported storm snow instabilities quickly settling out and not exceptionally reactive over the weekend. The snow layering ended right side up with low density snowfall at the end of the storm. 

East winds both through the Cascade passes and along ridgetop began to increase Monday and persist Tuesday. This has transported loose surface snow to some lee slopes, on more S-W aspects. The most recent storm snow avalanche problem should be over, however recent wind slab will remain an issue with certain aspects, generally near and above treeline.  

NWAC observers in the Crystal Mountain backcountry Tuesday, did see evidence of recent wind transport from strong E-NE crest level winds.  However, wind slab formation was highly variable and no triggered releases were noted. Good low density, unconsolidated snow ranging from 25-35 cm was unreactive and gradually increased in density down to a well bonded rain crust buried 50-55 cm. NWAC forecasters and WSDOT working on the Chinook Pass weather station Tuesday made similar observations.