Posted 8:05am, Saturday, January 29th, 2011
Tuckerman Ravine: The Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. The Lobster Claw, Right Gully, Left Gully, Hillman’s Highway, the Lower Snowfields, and Little Headwall have Low avalanche danger. Natural and human-triggered avalanches are unlikely in these areas.
Huntington Ravine: All forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely in these areas. Watch for unstable snow on isolated terrain features.
There are two key components to today’s advisory: first are the instabilities already out there, second are the ones that may be developing today. The existing instabilities, most notably in the areas of Tuckerman rated Moderate, are a result of a handful of light snowfalls over the past week combined with a variety of wind speeds and directions. The snow was able to load into well-protected areas such as under the ice in the Headwall, in parts of the lower Lip, and in the Chute. In these areas you can find energetic and reactive slabs interspersed with areas of snow that don’t give as much cause for alarm. To some degree, I believe solar gain early yesterday helped to stabilize slopes facing due S, but the farther around the Headwall you go toward the Chute, the less this would have happened. Using your skills to recognize potential instabilities and navigate around them can help you mitigate the avalanche hazard today. Of course, it is a Saturday, so you’ll want to be wary of potential human triggers that might be stomping around in your vicinity. Most of these areas of note are in parts of the Bowl that you can see from below, but clouds might limit visibility today and you still might need to contend with the second key component today–new slab development.
About 1.5″ (4cm) of very light density snow, generally 2-4%, fell yesterday and is continuing today. We might get around another inch (2.5cm) through the daylight hours as well. The winds are forecasted to be only 10-20mph (16-32kph) from the W. This is rather calm for Mt. Washington, but with snow densities being as light as they are it won’t take much of a gust to blow this snow in the direction of the ravines. Any new slab that is able to develop today will also be low density and soft. This is the type of slab that you might not recognize to be slab if you’ve only spent time in eastern mountains. It can be very soft and touchy, meaning that it doesn’t take much impact at all to initiate and propagate a fracture. Expect this development to take place in the upper elevations of the forecast areas, particularly those with an E-facing aspect.
Although I focused this discussion mostly on Tuckerman, the same factors are at play in Huntington Ravine. The biggest difference is that the overall size and distribution of existing slabs is small enough that they only qualify as isolated pockets of unstable snow, hence the Low rating. The problem related to developing soft slabs during the day may be taking place in Huntington, as well.
- 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.
- This advisory expires at midnight. 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