Avalanche Advisory for 2016-01-07 06:41:07

Yesterday, in a word, was deep.  The back to back storm systems over the past couple of days has brought close to two feet of new snow to the area.  Combined with the new snow has been moderate winds, and a buried surface hoar layer that formed during the few clear and cold days preceding these systems.  This has been a recipe for CONSIDERABLE avalanche danger for elevations near and above treeline with scattered pockets below treeline.  Observations made yesterday by both myself and those who ventured out yesterday confirmed these danger ratings as accurate.  A report from individual who made it out to Ash Cr Butte outlined their observations at that location in our forecast area.  A snow study pit was dug at 7,700 ft. on a north facing aspect with a 30 degree slope angle.  Total snow depth at that location was recorded at 235 cm with 65 cm of new snow on the buried surface hoar.  An extended column test was performed scoring  ECTP23 Q1 at 65 cm deep, sudden planner.  A naturally triggered avalanche was also observed off of the same aspect at a higher elevation which ran all the way to the bottom of the bowl traveling 800 vertical feet.  Evidence of wind loading and cornice formation were observed above treeline as well.  

I made a tour yesterday up Green Butte Ridge in search of the buried surface hoar below treeline.  Just as you reach the very bottom of Broadway I skinned over to the West aspect that drops from the ridge top into Avalanche Gulch.  I dug a snow study pit on that aspect right at 8,000 ft. with a slope angle of 30 degrees.  The buried surface hoar was hard to identify visually between the layer of old snow from last weeks storms, and the new snow on top.  It wasn't until I performed an extended column test that surface hoar layer presented itself.  The results from the EC test was a score of ECTP19 Q2.  The surface hoar crystals were easy to identify under a looking glass, but showed signs of decomposition.  I believe this persistent weak layer created by the buried surface hoar will remain a problem today on protected W-NW-N-NE aspects at and below treeline.  Backcountry skiers/splitboarders/snowmobilers should avoid open slopes of 32 degrees and steeper near and below treeline.  

Wind conditions with these most recent storms has been perfect for wind slab formation near and above treeline. Visibility may prevent folks from pushing much above treeline today, but if one were to travel there avoid areas with wind slab formation on leeward W-NW-N-NE-E aspects.  Wind has the potential to load leeward slopes 10x faster than falling snow, and creates a more dense layer on top of less dense snow. The high precipitation rates during yesterday's storm combined with steady moderate winds equals increased avalanche danger.

Storm slabs will remain a concern as well as they relate directly to the buried surface hoar PWL avalanche problem.  Natural avalanches will be possible and human triggered avalanches will be likely near and above treeline.  Below treeline natural avalanches will be unlikely, but human triggered slides will be possible.  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 conservative decision making.

1/6/2016-Full Pit Profile by Jon Dove:

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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.