Avalanche Advisory for Friday 1-6-2012

Expires at Midnight Friday 1-6-2012

Tuckerman and Huntington Ravines have CONSIDERABLE avalanche danger today.  Natural avalanches are possible and human triggered avalanches are likely.  The only exception to this is North Gully in Huntington which has Moderate avalanche danger.  We have not begun forecasting for the Lobster Claw, Right Gully, the Lower Snowfields, or Little Headwall in Tuckerman and the Escape Hatch in Huntington due to a general lack of snow in these areas.  Daily forecasting will begin for these areas when conditions warrant although avalanche activity may occur before this point.

As forecasted yesterday the higher summits were obscured by fog and blowing snow all day.  The summit reported 2.4” (6cm) of 7% snow on increasing winds from the West.  In the mid afternoon velocities peaked at 89 mph (143 kph) vastly exceeding expectations.  This was also the period of maximum snow loading into the Ravines.  Snow will continue today with up to another 3” of new accumulation carried in on West winds with speeds from the current of 35mph (56kph) to over 70mph (112kph) this afternoon.  This will generate some heavier denser slabs through the day over some loose unconsolidated snow and very soft slabs deposited this morning.  This is particularly true in strong lee areas protected from W winds.  This is all occurring on top of the issues that built through the day yesterday which caused yet another avalanche accident in Huntington Ravine late in the day.  Areas in the direct lee of West winds will be the primary areas of concern earliest today with adjacent aspects following behind.  The Lip through the Center Headwall and over to Left Gully would be the focus locations to worry about in Tuckerman while over in Huntington Ravine Odell, Pinnacle and Central will have more instability issues than gullies such as Yale or Damnation.  It’s important to remember that each forecasted rating is not a point on a line but a spectrum.  Some outlying aspects will be on the lower end of “Considerable” while others may be in the middle or upper end of the definition.

There is little doubt that we will have unstable snow issues today and into the weekend.  More snow tonight and tomorrow may deposit another 2-3” (5-7.5cm) on 40-70mph (64-112kph) winds along with increasing temperatures making for heavier snow, therefore denser slabs.  The slow accumulation over the past week will add up to around a foot (30cm) of accumulation over the past 7 days by tomorrow which can be a little trickier to deal with than a big dump.  This scenario often lets multiple layers to develop with just enough strength to stay put waiting for a trigger.  In a big storm avalanche cycles usually occur because the snow strength can’t handle the rapid load.  Because of the multiple layers out there you will need all your avalanche senses and skills today and through the weekend.  Expect to find a mix of conditions such as some scouring down to old bed surfaces in areas open to wind hammering right next to unstable slabs.  I would prepare for widespread instabilities perhaps above you or adjacent to your position.  We will have some avalanche incident discussion on our Incident page today as well as in the “Weekend Update” this afternoon.  So check back to learn more about the upcoming weekend and lessons learned from the 2 avalanche accidents/incidents this week on www.mountwashingtonavalanchecenter.org .

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 8:50.  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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