Posted 8:13a.m., Monday, April 18, 2011
Tuckerman Ravine has Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. You’ll need to evaluate snow and terrain carefully to identify the particular areas of concern. The only exceptions to the Moderate rating are the Little Headwall, Lower Snowfields, Right Gully and Lobster Claw which all have Low avalanche danger. In these areas natural and human-triggered avalanches are unlikely but you’ll want to watch for unstable snow on isolated terrain features.
Huntington Ravine is under a General Advisory. You will need to do your own snow stability assessments when using avalanche terrain in Huntington Ravine. A danger of falling ice exists and will persist until it all comes down.
After some gross weather to end the weekend we’re back to winter on the mountain. This morning the summit sits at 10F (-12C) and blowing snow fills the air. Freezing rain coated the mountain early on Sunday and the mercury on the summit peaked at 32F (0C) during the mid morning hours. By that point the Observatory had recorded 3.5” (9cm) of new snow and mixed precip which was blown in on southern winds. As a cold front moved through during the late morning the temperature began to plummet and winds swung to the west. Some snow was initially protected and unavailable for wind transport thanks to the thin crust that had been laid down by the sleet and freezing rain. Shortly before midnight last night wind speeds ramped up and began blowing with steady speeds around 70mph (113kph). Yesterday’s snow began to be pushed around by the winds and light snow showers have added to the mix through the early morning hours. Clouds and blowing snow are not allowing us to pick out any visual clues this morning but if we had a view we’d expect to see a variety of surface conditions. Areas that are exposed to W winds likely have large areas of scouring where new snow has been unable to adhere to the “packed powder” that provided loud and scratchy turns on Saturday. Other spots that are sheltered from W winds have likely developed new windslab that poses today’s main concern. Protected areas with an easterly aspect are the most suspect and I would expect to find the greatest instability below the Headwall ice, in the Chute and in the mid elevations of the Lip. While the Lip area has the benefit of spring moguls to roughen up the potential bed surface the Center Headwall has been much smoother and would make me more cautious. I don’t expect the new windslab to be widespread but I do expect it to be reactive to a human trigger as it attempts to cling to the old icy surface. With all that said, today may provide some good conditions for mountaineering but few decent options for skiing. Cramponing should be fantastic where you can stay on the old surface. Left Gully and Hillman’s Highway are on the lower end of the Moderate rating and you should be able to avoid most of the issues with good route-finding. Unfortunately I think the skiing in these locations will probably be junk. The same can be said for Right Gully and Lobster Claw where I would expect mostly old surface with isolated pockets of windslab on the climber’s left hand side. Sliding falls are a major concern in all of these areas so take a good look at your run-out before deciding what you’ll attempt today. The best skiing would probably be on the new snow in the areas of most concern. Today’s windslabs might not be all that large but don’t forget to analyze the consequences before you click in.
- 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 caretaker at Hermit Lake Shelters.
- This advisory expires at midnight. A new advisory will be issued tomorrow.
Justin Preisendorfer, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856