All forecast areas of Tuckerman and Huntington Ravines will have CONSIDERABLE avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Lobster Claw, the Lower Snowfields, and Little Headwall are not posted due to a lack of snow in these areas.
AVALANCHE PROBLEM: The threat of Wet Slab avalanches is the main concern today. Warming temperatures will weaken existing slabs, many of them 2-3’ thick or more, while up to ½” of rain may overload them, potentially causing them to fail. The largest, most destructive avalanche activity would likely occur in Sluice through Chute, and Central Gully in Huntington. These are areas with the largest continuous wind slab with known weak layers beneath. Terrain like northern Huntington gullies, Odells and South could also spawn wet slabs and shouldn’t be underestimated.
WEATHER: Cold air dammed against the mountains and pooled in the valleys is creating conditions for a nasty glaze of ice to grow on surfaces. Meanwhile, mid-elevations on Mount Washington are above freezing and are expected to remain there for the next 12 hours or so for a total of 18-20 hours above freezing in our forecast areas. The warm front bringing today’s precipitation will be followed by a cold front with dry conditions. Temperatures will dip down below freezing in the early evening hours, improving snow stability in the process, but not before exposing our snowpack to warm temperatures and rain.
SNOWPACK: The old wind slabs, mentioned in the avalanche problem section above, have weak layers consisting of rimed particles and graupel with some early, developing near crust facets depending on aspect and thickness of overlying slab. These slabs can almost be called persistent slabs at this point due to their longevity. Our avalanche activity will likely peak today due to the rain and warmth on the slabs above these weak layers. It is conceivable that the settlement of the snowpack that began last night will reduce the threat of smaller avalanches in lighter density snow nearer the surface but I still consider wet loose avalanche if I was out this morning due to the heavy rain currently falling on the mountain. The real concern is the notoriously hard to predict wet slab activity today. Fortunately, our weather today is not the kind of weather that will drive people out into our terrain because human triggered avalanches in our snowpack today are likely.
Please use the Summer Lion Head Trail. The Sherburne Ski trail is closed ½ mile from the parking lot.
- 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., Friday, March 25, 2016. A new advisory will be issued tomorrow.
Frank Carus/Helon Hoffer, Snow Rangers
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2716