Avalanche Advisory for 2016-03-11 07:12:51

After yesterday's outing, soggy and wet are the first two words that come to mind! Multiple objectives including snowpack analysis and weather station repair brought myself and a hardy volunteer up to Gray Butte via Bunny Flat, Mt Shasta. Warm temperatures in the morning, 6 degrees warmer than the day prior, should of been a good clue for what the day had in store. Snow struggled to fall at the 6,000 foot level. Elevations below that received mostly rain on snow. Look up at the mountains from town and you'll see where the snow starts to stick to the trees. For most of the day, a healthy serving of pea soup was the standard. Heavy mist, light rain and snow fell up until mid-late afternoon when a brief clearing gave way to decent visability and a glimpse at the mountain and surrounding hills. This leads me to my next point of discussion, the snowpack.

My partner and I did not observe any recent avalanches or eyebrow raising signs of instability yesterday on Gray Butte or the south side of the Mt Shasta. This is actually a bit concerning and makes me nervous. I would place good money that with the rapid precip rates, heavy snow, wind and several decent bed surfaces in place that we'd get some sort of action out there. Because we have not seen any avalanches/signs of instability occur... this leads me to believe that either - A) Continued ample snowfall will eventually cause a slab to fail and a big one at that, or B) the warmer temperatures of late have consolidated the snowpack into a stable, sticky, wet mass. I'm not quite on board with option B and lean more toward option A, especially since several more feet is very likely overt the weekend.

A snowpit was dug on a NW facing slope at 7,640 feet on Gray Butte, 35 degree slope. Two weaknesses in the snowpack were revealed, though seemingly not under high tension. Compression tests (CT14@20cm from top-Q3) failed fairly easily with poor shear quality/fracture character at 20 cm deep from the snow surface. This seemed to be simply a density change in the snow. Extended column tests (ECT24@47cm from top-Q3) failed at 47 cm deep in the snowpack, just below the March 7th crust layer. This ECT result was very similar to the day prior. Overall, 83cm of new snow since Sunday was recorded at this location. Our March 7th crust layer still exists and otherwise an isothermal, moist snowpack exists both below and above the 3/7 crust with 1 finger density hardness below the crust and fist to 4 finger hardneess above the crust. Moist and heavy keep coming to mind for our day, and the snow.

So...what should we make of this? Here is my thoughts: Stability tests and visual clues leaning toward an unstable snowpack are few. A couple roller balls occured yesterday...not a big concern unless on steep slopes with a long fetch. New, heavy snow continues to build, rapid precipitation rates are guaranteed, wind will blow and move snow around this weekend... We have several signs of the classic "5 Red Flags of Avalanche Danger" in place. As we move through these storm cycles this weekend, it's going to be very important to proceed cautiously if in avalanche terrain. We are getting to the point where large avalanches could be possible. Always look for signs of instability, NOT stability. If you don't find anything, keep looking. 

Above treeline, we got a brief glimpse at things late in the day, but due to very poor visibility lately, hands on assesment of the snowpack has been nill. The Castle Lake road is closed and thus access difficult up there. Almost entirely rain on snow has been occuring at Castle Lake. On Mt Eddy, only the highest terrain has been seeing new snow. We do not have any recent obs from the Eddy area.

Today, all avalanche prone slopes with ample new snow, wind loaded leeward ridgelines, cornices...it should all be suspect. The snow is piling up quickly and is heavy. Existing wind slabs will continue to build in size with steady precipitation expected today. Southerly winds will load NW-N-NE-E-SE slopes. Changes in temperature and snow levels will create different density snow layering. It's often that these density changes act as the weak layer. Your 'A" game is going to be necessary and it might just be a good idea to stay off avalanche terrain entirely. Periods/pockets of HIGH avalanche danger are possible immediately during or just after these storms.

LEFT: Snowpit at 7,640 feet, NW aspect of Gray Butte, Mt. Shasta. Note crust layer / RIGHT - March 7th sun crust layer, 1-2cm thick. 
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LOCAL AREA ROAD, NORDIC, AND SNOWMOBILE PARK STATUS:

The Sand Flat cross country ski trails are in good shape and ready for your cross country skis and snow shoes.  These are backcountry routes 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 have not been groomed in the past week and a half due to warm temperatures.  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 CLOSED at the gate. The culvert blew out and we do not know when it will be repaired. 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.