Avalanche Advisory for Saturday, December 24, 2016

Huntington Ravine has MODERATE avalanche danger. All forecast areas have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Evaluate snow and terrain features carefully to identify features of concern.

 Tuckerman Ravine has MODERATE and LOW avalanche danger. Sluice, The Lip, Center Bowl, Chute, Left Gully and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Right Gully has Low avalanche danger. Natural and human-triggered avalanches are unlikely. Lobster Claw, Lower Snowfields and the Little Headwall are not rated due to a lack of snow.

AVALANCHE PROBLEM: 1-3” of new snow today with increasing wind speeds will create wind slabs in our forecast areas. The size of these wind slabs will depend on the total snow received. If the upper end of the forecast amount falls, expect some medium sized human-triggered avalanches to be possible in areas like the Lip, under the ice in Center Bowl and above the choke in Chute and in good sized portions of Central Gully. If we receive 3” of new snow, anticipate natural avalanches becoming more possible than unlikely later in the afternoon and evening as winds ramp up into the 60-80 mph range. There is a possibility that our forecast elevations will receive some of this precipitation as rain, but it is unlikely that enough rain will fall to create a wet slab problem.

WEATHER: Though the summit weather forecast is calling for snow today, current temperatures lower on the mountain have us crossing our fingers that temperatures will cool sooner than hourly forecasts currently indicate. Temperatures on the mountain continue to rise this morning and are approaching 40F at Hermit Lake. Light snow shower activity should begin in the morning and continue during daylight hours as a weak low passes. Temperatures will drop later in the afternoon with winds increasing to the 60-80 mph range.

SNOWPACK: Wind slabs which developed Thursday and Friday were unreactive yesterday.  Warm temperatures (38F at Hermit Lake) this morning are helping this layer to settle further. Stability tests also revealed that snow was bonded pretty well to the old melt/freeze crust with density changes in the snow serving as the weak layer. The surface skin of wind slab was variable in thickness and tough enough to resist sustaining a crack for any distance. These wind slabs were widely scattered thorough the terrain with lots of old surface providing safe travel options for avoiding suspect areas. Given today’s wind speeds and snow fall totals, expect a similar picture today and tomorrow, though visibility will be challenging as clouds descend and blowing snow flattens light. The refrozen crust is hard enough to warrant crampons as terrain steepens but is breakable off trail so expect post-holing in less travelled terrain.

The Lion Head Winter Route is open and the most direct route to the summit. The Tuckerman Ravine Trail bridge is completed enough to allow traffic again so you can avoid the detour. Please be careful of construction debris near crossover 7 on the Sherburne Trail and watch out for machine traffic since the Tuckerman Ravine trail is still not really passable for snow machines. Thanks for your continued patience!

Please Remember:

  • 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 7:45 a.m., Saturday, December 24, 2016. A new advisory will be issued tomorrow.

Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2716