Avalanche Advisory, Thursday 1-12-2012

Expires at Midnight 1-12-12

Tuckerman and Huntington Ravines will have HIGH avalanche danger today.  Natural avalanches are likely and human triggered avalanches are very likely. Travel in avalanche terrain is not recommended due to the developing very dangerous avalanche conditions. Some areas are not yet posted due to the overall lack of snow. These include the Lobster Claw, Right Gully, the Lower Snowfields, and the Little Headwall in Tuckerman and the Escape Hatch in Huntington. Forecasts for these locations will begin when conditions warrant.

Finally, a winter storm for the mountains!  We are expecting 6-12 inches today depending on the exact track and cold air infiltration moving into the system.  Very cold air to the north mixing with the low pressure coming from the south should keep precipitation all snow in the higher mountains and particularly in the Presidentials.  Snow is being brought in on winds from the SE currently around 30 to 40mph (48-64kph). Velocities are expected to ramp up into the afternoon eventually getting to 70 mph (112kph) with higher gusts.  This will occur during and after periods of heavy snow at S-2/3 intensity rates (2-3cm’s an hour).  All of this together makes it clear new snow loading will generate unstable slabs creating an increasing avalanche danger.  Aspects with a northerly component namely portions of Hillman’s Highway, Left gully, South Gully and Odell should reach the forecasted avalanche danger rating first.  These areas will be followed soon there after by slopes facing the east that have some terrain features adjacent to them.  These locations will be cross loaded by SE winds so expect the protected lee to have building instabilities as well.  Areas pointing directly into the wind such as the Sluice, Yale, and Damnation will struggle to reach the “High” rating. 

The forecasted snow totals are pretty wide for the higher mountains, 6-12” (15-30cm). Forecasting avalanche potential for 6” is obviously different than 12” and would generate different rating choices within the 5 scale rating system.  To assure we don’t under rate the danger level, today’s postings are with the expectations that we end up on the upper level of accumulations, 9-12” (23-30cm).  Forecast areas will move quickly to the lower end of “Considerable” and climb through the rating during the morning and be bumping against the “High“ rating if we receive the aforementioned snow amounts associated with the max wind speeds of 70+mph (112kph).  Although we are most concerned about daylight hours we are taking into account the period of maximum instability that will occur after dark.  So to summarize, we will be in an increasing avalanche danger trend from now until after dark with the potential for natural avalanches beginning later this morning and becoming likely later in the day.  Keeping a close eye on snow totals today is the critical bulls-eye factor to track.  If we end up in the 6” range the “High” ratings will not be reached.

Winds will shift from the SE to the W overnight and into the tomorrow gusting over 75mph (120kph) along with a drop in temperature.  Additional snow from a secondary system is also expected to deliver another 3-5” (7.5-12.5cm) tomorrow.  I would expect an elevated avalanche danger into the holiday weekend.  The mercury should continue to drop well below zero into Saturday and Sunday so any slabs developing over the next 48 hours will likely retain their elastic energy deep into the weekend.   Be sure to check back for the most recent avalanche advisory and our Weekend Update that will be posted early Friday 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 8:40am.  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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