Wednesday, January 7, 2009

      Created at 7:09 am

Forecaster: Drew Hardesty

   

BOTTOM LINE


   

   Pockets of HIGH danger exist in steep wind loaded terrain at the mid
   and upper elevations on slopes approaching 35 degrees and steeper. Any
   avalanche triggered on a northwest through northeast through southeast
   facing slope may step down to near the ground. Consequences of being
   caught are likely fatal. Wet activity harbors a MODERATE danger at the
   low elevations up to 7500' on all aspects.You may get impressive push a
   lanche debris piles into terrain traps today if you're not careful.

CURRENT CONDITIONS


   

   Looks like we're winding down from the powerhouse that effectively
   began on Monday. Overnight, the Cottonwoods and Park City mountains
   squeezed another 4-6" of very heavy snow out of the dregs of the storm,
   pushing storm totals to 32" in Little Cottonwood, and nearly 12-20" in
   the Ogden, Provo, and Park City mountains. With a rising temperature
   trend to make a coastie feel right at home, densities doubled in the
   last 12 or so hours: we now have 14% or more sitting on top of 5-8% of
   settled fluff. The rain/snow line bumped toward 7000' and observers
   this morning have reported some minor wet activity above the roads. The
   winds may be stealing the show. They've been blowing pretty good from
   the west and northwest since the beginning of the storm and this
   morning accelerated to 45-50mph with gusts to the mid-80's. Even the
   more protected areas are gusting into the 30's and 40's. Temps are in
   the low 20's at 10,000' and upper 20's at 8000'.

RECENT ACTIVITY


   

   UDOT avalanche control teams dumped up 4-8' deep piles of snow on the
   roads while ski patrol teams triggered numerous soft slabs up to 2'
   deep. Few ventured into the backcountry.


THREAT #1


   

                     


   
   
   

   From the disastrous avalanche cycles in the northwest during the winter
   of 1909/1910, then District Weather Forecaster Edward Beals wrote


   "It was not the quantity of snow alone which fell this year that caused
   so many avalanches, but it was the manner in which it fell, and many of
   the people most familiar with these phenomena knew a day or two before
   they occurred that slides were inevitable, and had they not sought
   places of safety more lives would have been lost than were under the
   existing conditions."


   We are seeing the same things now: it's not just how much has fallen,
   but how it has fallen, and what has accompanied it. Rising
   temperatures, strong winds, high snowfall rates, an arguably somewhat
   weak old snow surface. It all adds up. Lost in the overnight hours are
   the natural avalanches that have already occurred. The continued winds
   will no doubt initiate some more in the storm snow and artificial
   triggering  is also a certainty today
   on steep slopes, particularly in areas drifted by the winds.

THREAT #2

   

                     


   
   
   

   Deep slab avalanches may also release with the added stress of a new
   snow avalanche in the usual terrrain .

THREAT #3

   

                     


   
   
   

   Wet activity will also become a danger at the elevations under about
   7500', particularly in heavily treed areas. Roof-a-lanches will also
   become a serious concern with the warming temperatures. Many steep
   roofs are likely to shed their new weight today, if they haven't
   already.

MOUNTAIN WEATHER

   

   We'll have mostly becoming partly cloudy skies today. The west to
   northwest winds are also expected to relax by the early afternoon and
   blow a more reasonable 30-35mph. Temps will continue their upward march
   to 25 at 10,00' and just below freezing at 8000'. We'll get a quick
   break tonight and tomorrow ahead of Thursday evening's storm, which may
   produce 7-10" for northwest flow favored areas.