Avalanche Advisory for Friday, 2-24-2012

This avalanche advisory expires at midnight Friday, 2-24-2012

Tuckerman and Huntington Ravines have MODERATE avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible.  Heightened avalanche conditions exist on specific terrain features.   Evaluate snow carefully to identify these areas of concern.  Many caveats exist today so read on for details below. The Lower Snowfields and the Little Headwall are not posted due to an overall lack of snow although they are getting close. Forecasts for these locations will begin when conditions warrant.

Over the past 24 hours the summit received 2.3” (5.75cm) of new snow which adds up to 3.9” (10cm) over the past 2 days.  New snow was delivered on a shifting and increasing wind which peaked yesterday afternoon from the NW at 81mph (128kph).  This loaded most of our avalanche terrain across both Ravines with numerous new slabs.  Early this morning the summits cleared offering some brief visibility before they become socked in again with the approaching weather system.  This event has put the region under a WINTER STORM WARNING from 1pm this afternoon until tomorrow morning.  At our forecasters meeting this morning we had a good discussion on how to handle the danger ratings today with the approaching precipitation and exact timing of new snow.  We feel “Moderate” covers the reality of current instabilities this morning well, in Tuckerman particularly from the Sluice over to the Chute which harbor our most significant concerns.  Of all our forecast areas we believe a human trigger has the greatest possibility to cause the fracture and failure of slabs in the strong lee areas created by the high W and NW winds on Thursday. In Huntington, Central and Yale are currently at “Moderate” with the other gullies sitting at “Low” danger as of 7am, but these should come into the “Moderate” rating late this afternoon pushing dusk.  Unstable pockets can be found in these “Low” locations this morning however they can be avoided by a mindful climber.  

As light snow begins to fall as early as this morning it will be associated with very light SE winds from 10-25mph (16-40kph) and increase to 35mph (56kph) through the day.  During day light hours we aren’t expecting much more than an inch …maybe two (2.5-5cm) of new snow blanketing the mountain.  Snow will intensify this evening with a building wind that will wrap and blow from the W.  If you adhere to the strict timing of this advisory lasting to midnight, the “Moderate” rating should be busting at the seams by that point.  Natural avalanche potential will be building after darkness with the definition of “Considerable” coming into play in some places before pumpkin time at 12 midnight.  This transition should occur so late in today’s advisory window that calling areas “Considerable” would be overstating the situation for daylight today, hence the “Moderate” forecast.  

It would be a very good day to be conservative in your overall plans to absolutely assure you are not benighted.  As snow intensifies overnight the higher mountains should hit somewhere between 6” and 10” (15-25cm) with winds ramping up substantially, raging to around 110mph (176kph) from the WNW on Saturday.  With this scenario I could envision the mountains reaching maximum instability, with “High” danger conditions, between 2 and 6am Saturday morning before subsiding slightly for the meat of Saturday.  For all of this to play out as described, timing is everything!  The main bulls-eye points to remember are as follows; 1. We are on an increasing avalanche danger trend beginning later this afternoon; 2. A “High” danger will likely be achieved sometime before the Saturday avalanche advisory issuance; and 3. Expect full arctic extreme conditions above treeline on Saturday as temperature hover around zero F and winds gust to 110 mph (176kph); 4. It will be critical to read Saturday’s Avalanche Advisory before heading up the mountain tomorrow and suggested you read our Weekend Update early this evening.

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