Avalanche Advisory for Wednesday 1-25-2012

This advisory expires at midnight Wednesday 1-25-2012.

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 warranted.  Recognize avalanche activity may occur within these areas before forecasts begin.

Snowpack lockup is underway as the concrete cures with the dropping temperatures.  All elevations climbed way above freezing yesterday with the exception of the summit which flirted with the 32-33F (0C) mark.  The melt water from warm conditions, in addition to copious amounts of rain, have deeply penetrated our snowpack making isothermal conditions up until the overnight when the mercury fell sharply.  The current “lockup” is occurring from the surface down as liquid free water in the snowpack freezes creating a thickening crust, which in turn is increasing the snowpack strength.  The crust will vary in strength, but expect breakable surface conditions off packed trails and very hard slick conditions on pack surfaces.  As strength increases, angled terrain will get very slick and hard which will make crampons and an ice ax worth their weight in gold!  Skillful use of these tools will be critical in the case of a slip, trip, or fall to keep you from achieving Mach 1 down steep slopes.  The drag co-efficient between ice crusts and modern Gore-Tex isn’t much so be ready to arrest a stumble very quickly with your mountaineering axe.  Use caution descending steep terrain and be ready for sudden deep post hole plunges through the crust.  Ice climbers should anticipate the growing problem of “ice dams” which usually occur after a mid-winter rain or thaw.  Freezing temperatures begin creating new ice at choke points which puts water flow under increasing pressure looking for a way out.  Often this way out is an ice tool or crampon hole which can unleash an eruption of ice and water.  This phenomenon has blown numerous ice climbers off their stance over the years.  This hazard generally dissipates with time but can be persistent in isolated areas for many days and is unrecognizable beneath the surface. 

As the reset button has been hit we have little concern of any old snow instability that was on the ground prior to the rain event due to the “ bridging” effect of the increasing crust thickness.  However a slight attention should be paid to the upslope snow showers that are expected today forecasted to bring us about an inch (2.5cm).  As the mountain moves through today some very isolated instabilities may develop in lee pockets of W and NW winds gusting over 80mph.  As new loading occurs from some new snow today realize is will be loading on top of slick cold crusts which should make for weak bonds at their interface.  

The Lion Head Winter Route is now open. This is a steep route; an ice axe and crampons are highly recommended for safe travel. Please avoid the summer Lion Head Trail due to avalanche risk. The Sherburne Ski Trail will be challenging as it freezes up tight today.  Expect lots of deep frozen ruts and other frozen pleasures to negotiate.  Check your speed frequently and assure your boards have a fresh tune up for edging needs.

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 8:10am. 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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