Avalanche Advisory for 2016-01-06 06:59:01

Yesterday provided those recreating in the backcountry with a solid foot of powder snow to play in.  No avalanche activity or outward signs of instability were reported.  All the new snow accompanied by moderate winds brings a few different issues to the forecast area.  Our current avalanche problems include storm slabs, a potential persistent weak layer due to pockets of buried surface hoar near and below treeline, and our common wind slabs. Of most concern is the new snow on top of existing surface hoar formations creating a PWL (persistent weak layer). We've spoken of this widespread surface hoar that formed during the short cold and dry period this last weekend, and was observed in multiple spots in the forecast area.  Buried surface hoar is a classic weak layer and potentially dangerous avalanche problem. Above treeline is not a concern for this problem as wind scours the loose, dry hoar crystals keeping things tidy. Rather, below and near treeline where the feathery crystals were preserved, protected areas out of the wind and on cold, shady aspects....these areas are going to be the best areas for preserved surface hoar to be buried by new snow. Aspects NW-N-NE, 6,500 to 8,000 feet will host the best chance of said problem. As new snow accumulates and wind loading exacerbates accumulation, this only adds stress to the weak layer over a very short period of time. Southerly winds will only increase the chance of tipping the stress vs. strength ratio on these northerly aspects. Snow does not like rapid change.  My plan for today is to search out areas where surface hoar may have been buried and monitor any changes to the crystal structure of said surface hoar, and test the stability and bonding with the new snow above.

The second concern for today will once again be wind slabs at near and above treeline elevations.  Winds over the past 36 hours have been perfect for wind loading... not too windy to completely sublimate the snow, but a nice moderate wind to load leeward slopes to perfection. Wind has the potential to load leeward slopes 10x faster than falling snow, and creates a more dense layer. The high precipitation rates during yesterday's storm combined with steady moderate winds equals increased avalanche danger. Leeward W-NW-N-NE-E will be the most heavily wind loaded aspects near and above treeline.

The third avalanche concern for today is storm slabs.  In areas where surface hoar does not exist, and the snow has been sheltered from wind transport storm slabs could exist.  With 16-19 inches of new snow in the last 36 hours storm slabs are thick enough to easily trap and bury an individual.  

For today backcountry traveler should avoid open slopes of 32 degrees and steeper on all aspects above treeline due to storm and wind slabs.  Use caution in broad, openly spaced trees near and below treeline due to pockets of buried surface hoar creating a PWL.  Natural avalanches will be possible and human triggered avalanches will be likely.  Dangerous avalanche conditions exist today.  Safe travel techniques should always be followed, regardless of avalanche danger.  Only expose one person at a time to avalanche terrain, regroup in "safe" spots out of avalanche paths, avoid terrain traps, and practice conservitive decision making.

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The Sand Flat cross country ski trails are in great shape and ready for your cross country skis or snow shoes. These are backcountry trails marked with blue diamonds on trees. Trails are not groomed.  Snow shoers, please blaze a parallel trail to cross country skiers staying out of the skin track. Thank you, and enjoy!

The Pilgrim Creek Snowmobile Park is open! Trails are being groomed currently. Head to our "Education" tab on our website and find the snowmobile section for trail information, grooming status and other sledder resources!

The Five Red Flags of Avalanche Danger any time of year include:  1) Recent/current avalanche activity  2) Whumpfing sounds or shooting cracks  3) Recent/current heavy snowfall  4) Strong winds transporting snow  5) Rapid warming or rain on snow.