Avalanche Advisory for Monday, 2-13-2012

Expires 12:00 midnight, 2-13-2012 

All forecast areas of Tuckerman Ravine have MODERATE avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible. Please read the discussion below for more information about the danger rating today. The Lower Snowfields and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when conditions warrant.

All forecast areas of Huntington Ravine have LOW avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features. 

It’s yet another cold windy morning at Hermit Lake with very poor visibility. This is the kind of morning where you’ll benefit from having paid attention to the weather history over the past several days. You won’t get much for visual clues about stability until you are well into avalanche terrain and route finding can be challenging even if you are very familiar with the area. Allow me to take you on a brief tour of the weather from this past weekend. On Saturday, light winds allowed 1.4” of new light density snow to cover the mountain. Then, as night fell, winds slowly ramped up into the 60-80mph range. This pushed a lot of the new snow over into the Cutler River Drainage (i.e. Tuckerman and Huntington) and began to increase the avalanche hazard. Yesterday morning winds decreased slightly as temperatures began to plummet. Then, mid-morning yesterday, winds began to trend slowly upward again. This continues to the present time, with summit winds regularly gusting from the WNW at over 100mph this morning and a peak gust of about 118mph. Temperatures have begun to rebound, but it will take a while to pull up from the lowest temperatures yet this season.

Forecasting today’s avalanche hazard for Huntington is a little easier than for Tuckerman…strong winds have scoured the light density snow out of the gullies, leaving behind predominantly older, more stable snow. You may find an isolated pocket here or there to be careful with, but these will only be in very strongly wind-sheltered locations. Choosing Tuckerman’s avalanche danger rating today was a challenge. I don’t feel as though any of our ratings definitions really nail down exactly how I feel about Tuckerman Ravine. Let’s start with the weather history described above. We know that winds have been working around the clock to move snow into the ravine. During this morning’s increase in velocity, the wind likely picked up snow in all the nooks and crannies that lighter winds left behind. My experiences with this pattern lead me to believe the snow is being loaded into very hard slabs in much of Tuckerman. Some areas may even be getting scoured down to older surfaces (Left Gully is a prime example). The density of the hard slabs will prevent a person’s stress bulb from punching very deeply into the snow, and slab strength can bridge potential weaknesses in all but the thin edges of the slabs. Overall, I believe the potential for human triggered avalanches to be on the lower end. On the other side of the coin, new snow is being loaded into the ravines as I write. This is effectively increasing the load on the snowpack. This additional load could be all that is needed to trigger a nasty hard slab avalanche. I think the possibility for this exists today, though also on the lower end of the probability spectrum. So while a person probably wouldn’t be enough of a force to trigger an avalanche, the weight of additional loading could be. However, the likelihood of this scenario playing out isn’t so great that I’m compelled to call it Considerable danger. Today’s rating of Moderate reflects my overall impression of the avalanche potential in Tuckerman. I’d urge you to be cautious in your choice of route today, since the controls will be in the hands of Mother Nature today. You may not have much say in whether or not avalanches take place, but you certainly have a say in where you travel. 

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.

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

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