Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger. Central, Pinnacle, Odell, Escape Hatch and South have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. North, Damnation and Yale have Moderate avalanche danger. Natural avalanches are unlikely and human- triggered avalanches are possible.
Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. Lobster Claw, Right, Sluice, Lip, Center Bowl, Chute, Left and Hillman’s Highway have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Lower Snowfields has Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. The Little Headwall may still have open water.
AVALANCHE PROBLEM: Wind shifting to the west today will create more wind slab in our terrain. Much of the 16” of new snow yesterday remains tucked in lee features in the alpine zone and will be transported by today’s west wind. This wind shift has a history of prolonged loading and today’s forecast is no different. Anticipate significant loading to continue from a new direction as the wind increases today and digs into the drifts and snowfields deposited by yesterday’s wind. Another concern are the dense wind slabs pounded into our terrain by last night’s howling wind. Those slabs remain a concern, especially in areas of Tuckerman Ravine with a more southerly aspect. These more stubborn slabs may fail under the weight of wind loaded snow today, with or without a human trigger.
WEATHER: Snowfall totals collected from two snow study plots just below treeline show 13” to 16” of snow fell in the past 24 hours. During that period, wind wrapped around from the east through the north and ramped up into the 70’s and 80’s mph as it shifted though the northwest with a peak gust of 122 mph from the NNW. As the low pressure system pulls away today, wind will increase again and shift west. 1-3” inches of upslope snow, available low density snow on the ground and the shifting and increasing wind are the primary drivers of our avalanche problem today. Temperatures will fall into the -25F range on the summit today which will create a different set of problems.
SNOWPACK: Limited visibility is hampering our ability to observe recent avalanche activity but it isn’t too much of a stretch to assume the weak layer was yesterday’s new snow. Ice crust from the Christmas storm was largely swept out in many areas or is deeply buried and so is not much of a player at present in our steep terrain. The bed surface for yesterday’s activity was likely the firm, squeaky pencil hardness slab which were prevalent in our terrain and seen in our recent video posts. Some previously existing softer snow in the Sluice, Lip and Center Bowl could contribute to the volume of snow from an avalanche in the Bowl, if it hasn’t slid already. Yesterday’s wind direction most likely filled in areas low in the forecast area such as the Fan in Huntington and Lower Snowfields in Tuckerman so remain heads up even in this lower angled terrain. As mentioned above, Lobster Claw and Right Gully, which are often quick to stabilize, received a good wind loading and should be evaluated carefully.
The Lion Head Winter Route is the safer route to the summit on the east side. Both the Tuckerman and Huntington Ravine Trails as well as the Lion Head Summer Route pass through several avalanche paths and are challenging mountaineering routes with significant avalanche hazard.
• Safe travel in avalanche terrain requires training and experience. This bulletin 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 Harvard Cabin.
• Posted 8:23 a.m., Friday, January 5, 2018. A new advisory will be issued tomorrow.
Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856