Avalanche Advisory for Thursday, January 21, 2016

All forecast areas of Tuckerman Ravine have MODERATE avalanche danger. Heightened avalanche conditions exist on specific terrain features.  Natural avalanches are unlikely and human-triggered avalanches are possible. Lobster Claw, Lower Snowfields, and the Little Headwall are not posted due to lack of snow cover. Exercise caution in these areas.

Huntington Ravine is under a General Avalanche Bulletin. General Bulletins are issued when instabilities are isolated within forecast areas and are issued every three days or earlier if conditions warrant. Forecast areas in Huntington have less well-developed snowfields to produce avalanches, but understand instabilities in these smaller locations may exist.  It is critical that you assess snow and avalanche conditions if venturing into Huntington.

AVALANCHE PROBLEM: Wind slabs continue to be the primary avalanche problem.  Clouds and blowing snow continue to veil the Ravine which will limit the ability for an overall quality assessment.  Existing slabs will likely be strong and stubborn to human impacts bridging over weak layers due to very high winds in the past 72 hours.  However, expect the outer extent of some of these slabs to be thin and more prone to fracture and failure, initiating into the thicker hard slabs nearby. If this occurs expect the potential fracture to travel greater distances than in softer slabs.  Anticipate the possibility for an avalanche that could encompass the entire snowfield, only limited by terrain features such as cliff bands and ice features.  In very sheltered lee areas of W to NW winds you may find isolated softer slabs that could be easier to trigger.  These softer snowfields are only a small percentage of the overall snowpack and less of a concern than the higher consequence hard slab avalanche.

WEATHER: Full winter ice cream headache conditions continue today due to below zero F temperatures and very high winds.  Visibility is expected to increase later today and then even more tomorrow as a high pressure slides in.  Unfortunately, the storm that will slap areas south of us with multiple feet of snow shouldn’t do much for our mountains, but more on that tomorrow.  Skiing may actually be pretty good if you head into southern New England this weekend. Slight warming, as well as a significant wind drop, will occur over the next 36 hours making the mountains more user friendly as we move into Saturday and Sunday.  Expect winds to slowly taper to as low as 15mph by Friday night.

SNOWPACK: As discussed yesterday we have limited snowpack information and are basing ratings on the past several days of weather and historically like events.  Winds will stay high today, gusting into the 90’s mph (150’s kph), eventually backing off during the overnight.  However, even with the tremendous transport power of these winds there is limited snow available in the alpine zones, so generally we are on a trend of increasing stability.  Following high wind events on Mount Washington, where winds are sustained for long periods over 100mph (160 kph), the mountain is left with what we dub “Steel Slab”.  This very hard and strong slab has enormous bridging capability as well as tensile strength.  The outer edges, or occasionally mid-snowfield, are thinner and less tolerant of your weight and impact bulb.  These locations are typically the trigger locales for the adjacent stronger thick hard slabs. The spatial variability and the ability to navigate the proverbial minefield of differing slab thickness is difficult.

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 8:30 a.m. January 21, 2016. A new advisory will be issued tomorrow.

Christopher Joosen, Snow Rangers
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856