Avalanche Advisory for Friday, 2-17-2012

Expires 12:00 midnight, February 17, 2012

Tuckerman Ravine has CONSIDERABLE avalanche danger.  Naturally-triggered avalanches are possible and human-triggered avalanches are likely. The only exception to this is the Lobster Claw, which has Moderate avalanche danger. Naturally-triggered avalanches are unlikely and human-triggered avalanches are possible. 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.

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger. Yale, Central, Pinnacle, and Odell have Considerable avalanche danger. Naturally-triggered avalanches are possible and human-triggered avalanches are likely. North, Damnation, South, and the Escape Hatch have Moderate avalanche danger. Naturally-triggered avalanches are unlikely and human-triggered avalanches are possible.

The most important thing we want you to understand today is that avalanche danger will be rising. The later you are out on the mountain, the more likely you are to encounter unstable snow. So far, Mt. Washington has received 1.2” (3cm) of 10% density snow, and it is currently snowing at Hermit Lake. We are expecting an additional 1-3” (2.5-7.5cm) during the day and more coming overnight. Winds are going to be at an ideal speed and direction for transporting the 2-4” of available snow into the ravines today, blowing from the W at 35-50mph (56-80kph) early and ramping up to NW 50-70mph (80-113kph) with higher gusts in the afternoon.

Prior to the onset of new snow last night, both ravines had good stability. We’d been at Low danger for at least a couple days in all forecast areas. Today, the primary threat will be windslabs developing from the new snow and wind combination. Expect areas with a strong easterly aspect to develop instabilities first, followed by the adjacent locations. At some point today, I expect to have naturally-triggered avalanches in Tuckerman. I don’t think it’s enough probability to warrant a High rating, but if I were betting on where avalanches will happen today, the Center Bowl and Lip area is where my money would go. I have little doubt these areas will reach into Considerable territory. Other adjacent areas will also get there, but they’ll take more time as the bed surfaces first need to get smoothed out by early wind loading. In Huntington a similar story is playing out, the strong easterly aspects will rise most quickly, followed by adjacent areas. Central, Pinnacle, and Odell stand out for me as the areas of most concern here. Yale and South won’t be far behind, either. Pay attention to the depth of the new snow in Huntington, and be thinking about what could be developing in the gully up above you.

The winds and the potential for new snow will continue to increase into the night, which will allow slab development to continue as well. At this point, I think it’s safe to say there will be some avalanche danger to contend with if you’re coming to the mountain tomorrow. As we do every Friday, we’ll post an update on the Weekend Update section of our website later this afternoon. Also check back for new photos from yesterday’s field trip to the summit.

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

2012-02-17 Print Friendly