Posted 8:15 a.m., Monday, April 4, 2011
Tuckerman and Huntington Ravines will have CONSIDERABLE avalanche danger today. Natural avalanches are possible and human triggered avalanches are likely. The only exception to this rating is the Little Headwall which has Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.
In the wake of a very winter like weekend, we find ourselves focusing on another storm system that will create new snow stability issues. Unlike our last one that brought a foot of nice snow to the mountain, we will be dealing with a snow to rain situation. We are starting off the day with Moderate danger in most areas with the gullies on the south side of Huntington still at Low. We expect this to change today as snow falls on the mountain and is transported by increasing SW winds that will reach speeds of 50 to 70 mph (80 to 112 kph) with higher gusts by nightfall. Total snow accumulation is forecasted to be between 2 and 4″ (5 and 10 cm) before transitioning to sleet and rain. While this is a modest amount of snow, the increasing winds will be able to turn it into deeper wind slabs, especially on north and east facing aspects. Temperatures are expected to climb today so new snow will likely become denser as the day wears on creating an upside down snowpack on all aspects. This scenario will be our first concern that will cause our avalanche danger to increase to Considerable. The second is the seemingly inevitable transition to all rain in avalanche terrain. If you opt to thread the needle with the previously mentioned snow conditions, I would advise you get the heck out of avalanche terrain before it rains. Rain will cause instability to rise quickly in any new slabs that form today and it will start eating away at the strength existing wind slabs have. These existing wind slabs are abundant and relatively new, having been deposited as recently as yesterday. Rain is forecasted to continue tonight with periods of high intensity. I expect peak instability to occur tonight with the potential for some large slabs to rip out due to the chaos the rain will bring to the layered snowpack in the Ravines. Rain will continue into tomorrow before transitioning back to snow. Expect elevated avalanche danger to linger through the day tomorrow. Total water equivalent forecasted for the period, including what will fall as snow and mixed precipitation, ranges from around 1″ to 1.5″ (25 to 38 mm).
The Harvard Cabin is now closed for the season. Camping in the Cutler River Drainage is only allowed at Hermit Lake Shelters.
- 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
Brian Johnston, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856