Avalanche Advisory for 2016-02-07 06:41:08

Yesterday an attempt was made to locate wind slab formations and test their bonding to underlying snow.  A ski tour up Green Butte Ridge toward the edge of Powder Bowl revealed that snow conditions above treeline remain quite variable.  The crown of a recent wind slab avalanche (photo below) was observed 2/4/2016 on an ESE facing aspect, in a protected pocket along the top of Green Butte Ridge that drops into Old Ski Bowl.  It is not known when the slide occurred, however, it is a perfect example of our current avalanche problem.  This recent wind slab avalanche activity is what sparked curiosity about wind slab bonding.  A snow study pit was dug at just below 9,000 ft. on the SE aspect of Powder Bowl, on a 45 degree slope, just below cornice formations lining the rim of the bowl.  A quick pit profile was taken (see below), and an extended column test performed to test the bonding of wind deposited snow.  Lighter, 4 Finger to Fist density snow that had fallen on Wednesday had been wind transported to form a layer approximately 30 cm thick.  It was observed sitting on top of much heavier, Pencil density snow that had been wind deposited about 6 days prior. A score of ECTP 12 Q2 was recorded at a depth of 34 cm at the interface of the lighter density and heavier density snow.  The snow crystals at the interface were easily identifiable as stellars and dendrites that had not decomposed creating a weak bond.  This leads me to believe that this could be the case with other wind slab formations elsewhere on the mountain.  These formations are common all along Casaval Ridge, just under the ridge top on steep SE aspects, in protected areas around rock outcroppings.  They are also common on similar aspects on Green Butte Ridge, Sun Bowl, Powder Bowl, Giddy Giddy Gulch, and Anaconda Gulch.  

A ski descent of Powder Bowl crossed many kinds of snow. Firm, icy crust, wind sculpted pillows and scales, wind buff powder being melted by the sun, and incredibly sticky snow below treeline.  Warm temperatures and lots of sunshine will continue to encourage the transition into a more consolidated snowpack, and maybe even form some corn snow conditions around 9,000 ft. and below by Wednesday.  Overall, snow instabilities have been few and far between in the forecast area with weaknesses in the snowpack relatively hard to find.

For today, evaluate snow and terrain above treeline for any signs of wind loading on leeward S-SE-E-NE-N-NW aspects.  Isolated terrain, primarily on open slopes 37 degrees and steeper, the tops of chutes and couloirs, near rock outcroppings (especially on SE aspects), depressions, and along roll overs/convexities, will be the places that one would find and potentially trigger a wind slab avalanche.  Cold, shady, northerly facing aspects likely have the highest potential for wind slab trigger. Wind slabs on all aspects affected by sun will likely become more stubborn to trigger.

Climbing conditions are good for this time of year.  Casaval, or one of the other ridge routes, would be a good option over the next few days for experienced climbers.  Avalanche Gulch climbing conditions are good with relatively firm snow for decent boot packing.  Boot penetration of just 5 cm was recorded at Helen Lake this last Thursday.  That being said, the variable snow conditions will present a variety of surfaces to travel over.  Some post holing is possible during the warmest portions of the day and at higher elevations in wind protected areas.

Pit profile at just under 9,000 ft. on the edge of Powder Bowl, Mt. Shasta-2/6/2016 by Forecaster:

Below: Wind effected snow conditions at upper 50/50 Flat on 2/4/2016 - 9,800 feet, Mt. Shasta

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Below: Crown of wind slab avalanche, N/NE facing pocket along Green Butte Ridge on 2/4/2016

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LOCAL AREA ROAD, NORDIC and SNOWMOBILE PARK STATUS:

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. These trails can be accessed via the Everett Memorial Highway. Thank you, and enjoy!

The Mt Shasta Nordic Center is open! These beautiful, groomed trails can be accessed via the Ski Park Highway. http://www.mtshastanordic.org

The Pilgrim Creek & Deer Mountain Snowmobile Parks are 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 Castle Lake road is plowed to the lake. The Everett Memorial Highway is plowed to Bunny Flat.

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