Avalanche Advisory Thursday 1-19-2012

Expires 12:00 midnight, January 19, 2012

Tuckerman and Huntington Ravines have LOW avalanche danger.  Natural and human triggered avalanches are unlikely EXCEPT IN ISOLATED TERRAIN FEATURES. The Lobster Claw, the Lower Snowfields, and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when conditions warrant.

The mountains are basking in the sun’s glory this morning albeit a rather chilly start at dawn.  Temperatures overnight inverted as winds died down and the cold air aloft dropped into the valleys.  By the time daylight rolled around the base of the mountain was colder than the summit with a temperature of -5F (-20.5C) at Pinkham Notch.  If you have the right gear for being in the mountains with cold air today you will be treated by copious sun, beautiful vistas and low wind speeds from the SSW at 10 to 25 mph (16-40kph).

Very high winds over the past 2 days have done the job scouring the mountain of available snow and packing it into the nooks and crannies where protected from the wind.  This wind was associated with some upslope snow showers that generated under an inch of snow.  Generally speaking we have widespread hard scoured slopes in the two ravines and numerous locations showing crust.  An interesting snowpack development to watch for is some intense faceting under the most recent crust.  Facets will continue to grow with today’s cold clear air.  I would expect crusts to erode and lose strength as they become cannibalized by new crystal growth.   This will be something to consider during the next loading event.  A few locations have some new snow in the strong lee particularly in Tuckerman Ravine from the Sluice over to the Chute.  If you were hunting for avalanches and spent the day trouncing all over the Ravine you would likely find an unstable pocket or two, but generally these are easy to avoid by paying attention and sticking to hard old surfaces.

Later today winds will be on the increase, building to 25-40mph (40-65kph) with clouds moving into the region.  Snow will begin very late in the day, forecasted to accumulate by Friday morning in the 2-4” (5-10cm) range on winds from the S shifting to the WNW.  Escalating speeds overnight will load new slabs into both ravines overnight if the forecast plays out.  Expect an increasing avalanche danger overnight with elevated ratings beyond today’s Low danger advisory.  This will all transpire during the presence of cold air in the zero to -5F (-18 to -21C) range which will likely produce both low density snow and slabs that will retain their instability into the weekend.  Stay tuned and check tomorrow’s avalanche advisory.  

 The Sherburne Ski Trail has decent coverage at this time. You don’t need to work too hard to avoid exposed rocks, but you may see a couple. In addition, the breakable crust is a bit arduous under ski so expect some challenging conditions until more snow comes in.

Please Remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
  • Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
  • For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.
  • Posted 8:35am. A new advisory will be issued tomorrow.

Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

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