Avalanche Forecast

This stretch of high pressure has featured mostly sunny and warm conditions with light winds for areas west of the Cascade crest and at higher elevations. Local colder, cloudier and breezier conditions have been seen at lower elevations exposed to easterly flow. More of the same can be expected on Wednesday.

This weather provides a nice opportunity to check out a variety of surface snow conditions but be sure to watch for early season/low snow travel hazards. Early season terrain hazards include poorly covered rocks, vegetation and creeks, particularly at lower elevations.

Also, watch for shallow wet surface snow conditions on some steep sun exposed slopes, especially below rocks or cliffs. 

Strong high pressure has now been over the region for over a full week. Sunshine and very mild temperatures have been the story with cooler temperatures and areas of low clouds at lower elevations. This weather has allowed for overall strengthening and consolidation of an already strong snowpack. The snowpack is well consolidated with settled old storm snow of about 1 to 2 feet over the strong Thanksgiving rain crust. 

Some natural small loose wet slides have occurred on mainly steep sun exposed slopes over the last week, but have become much less frequent over the past several days. See observation below for a skier triggered loose wet above NWAC's forecast elevation bands. Active wind loading has not been observed since late last week.  

Surface conditions are highly variable. On solar aspects, surface melt-freeze crusts reform every night. On shaded and sheltered aspects, settled storm snow is still providing some nice skiing and riding conditions. Many aspects in higher terrain now feature wind stiffened snow. Near surface faceting and surface hoar growth has been reported on colder, non-solar aspects throughout the Cascades. These persistent grain types will become important when snowfall returns and watched as potential future weak layers. 

Observations

NWAC pro-observer Laura Green traveled in the Mitchell/White River drainage on Monday between 5300 and 6600 feet and found many variations in the surface snow but overall a settled and well bonded snowpack with few avalanche concerns in the terrain she covered.

One skier triggered avalanche was reported on the White River Headwall near Crater Rock on Sunday up to size 2 (see picture).  While this slide reaches above NWAC's forecast, it highlights the potential for loose wet avalanches on steep solar aspects.  

Photo courtesy Mike Schumann 12-10-17