Expires 12:00 midnight, 2-7-2012
Tuckerman Ravine has both LOW and MODERATE avalanche danger. The Lobster Claw, Right Gully, Left Gully, and Hillman’s Highway have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features. All other forecast areas in Tuckerman have Moderate avalanche danger. Natural 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 LOW avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features. Expect these pockets to exist and avoid them by staying to more stable older surfaces.
Yesterday morning the summit of Mt. Washington received 1.2” of new snow. They must be stockpiling it up there somehow, because very little made it down here to Hermit Lake. At our manual snowplots we only recorded a trace, but strong winds may have blown some off the boards. Although we can’t be sure how much snow actually fell into avalanche terrain yesterday, one thing we can be sure about is that the wind did transport snow into the ravines. A brief clearing window in the mid-afternoon allowed us to see that the tracks in the Sluice and Lip area had been filled in. We were also able to see an underlying older surface beneath the new layer in many areas. Taking it all together, we were given a good idea of the amount loading that took place.
Two snow stability issues stand out for me today. One is yesterday’s snow which created unstable slabs in isolated terrain features within areas forecasted at Low danger. These are most likely to be small in size and isolated from larger slopes or snowfields, however, you should still have your avalanche eyes open when you find yourself in areas of freshly deposited slab. This is particularly true this season, when the consequences of any fall are magnified by the thin snow coverage.
The second concern is found underneath the new surface. A variety of layers and interfaces can be found in the Moderate-rated locations. As usual, the depth and exact characteristics will vary depending on exactly where you are. The thread that ties them all together is the existence of two buried crust layers. The uppermost of these was the most noteworthy, acting as the sliding surface in all of our pits on Sunday. During this time, southerly aspects were receiving a good shot of solar energy, which helped stability of the uppermost snow layers on these slopes. In other areas, the sun wasn’t hitting so strongly, so they didn’t get this effect, such as the Center Bowl and Chute. If you dig deeper down into the snowpack, you’ll find another crust layer. To get this layer to fail would probably take a significant impact force. I don’t foresee a person doing this, but the weight of an avalanche on the surface certainly could. The point in mentioning this is that you should be thinking about more than just the upper layers sliding. The increased consequences that come along with a small avalanche are potentially severe.
- 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 8:15a.m. 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