Avalanche Advisory for Sunday, 12-30-2012

Expires at 12:00 midnight, December 30th, 2012.

All forecast areas of Tuckerman and Huntington Ravines have HIGH avalanche danger. Natural avalanches are likely; human triggered avalanches are very likely. Very dangerous avalanche conditions exist. Travel in avalanche terrain is not recommended.

It appears as though 2012 will go out with a bang…or maybe more like the roar of a freight train passing by. Not only has there been above average snow over the last two weeks, but the weather conditions over the next 36 hours or so will be especially fierce. These are conditions that should make you seriously consider (or reconsider?) taking a trip above treeline. Winds today will be steadily on the rise, reaching sustained speeds over 100mph (162kph) before dark. During this time, temperatures will continue to fall to below zero F (-18C). In the evening the trend continues, with even stronger winds and colder temperatures.

As you can probably imagine by now, spending time up high on Mt. Washington today has the potential to be a very challenging experience. So while there may not be a lot of people moving around up there, snow certainly will be on the move today. As far as avalanches go, what will happen today seems pretty clear. It’s an almost perfect setup situation for numerous avalanches in many areas.

Last night about 6″ (15cm) of light density snow fell during a period with summit winds generally less than 30mph (48kph). This new snow blanketed any existing snowfields and lower angle ice bulges, creating a nice layer of weak snow as the first step toward this avalanche cycle. Next, winds shifted to the NW and began to rise. As the newly fallen snow was in the 5-6% density range, it didn’t need much wind to start loading it onto the weaker layer. Continually increasing winds overnight and through today are going to keep layering heavier, denser slabs on top of softer, weaker layers. We expect this scenario to play out in most forecast areas today, so although the size of the avalanches are not expected to be very large, there is a strong likelihood that a single avalanche path may slide several times today. As if last night’s snow wasn’t enough, today’s winds will be strong enough to pick up any and all available snow from the windward side of the mountain and load it onto the eastern slopes as dangerous windslabs.

Today is a good day to stay out of avalanche terrain. This includes venturing very far up onto the floor of Tuckerman. Yesterday I saw avalanche debris in Odell Gully that had run almost to the flats of Huntington. Despite what I said about expected avalanches to not be very large, there is no reason to believe today’s avalanche activity will not run into low angle terrain at the base of slide paths.

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 8:15 a.m. December 30, 2012. A new advisory will be issued tomorrow.

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