Avalanche Advisory for Sunday, December 21, 2014

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has MODERATE and LOW avalanche danger. The Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully to identify heightened avalanche conditions and features of concern. All other forecast areas have Low avalanche danger where natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

Huntington Ravine has MODERATE and LOW avalanche danger. North, Damnation, Yale, Central and Pinnacle have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate the snow and terrain carefully. Odell, South Gully, and the Escape Hatch have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

AVALANCHE PROBLEM: The wind slab leftover from Thursday’s loading event is the primary threat today. This includes deeper sluff piles that have the tendency to act as areas of deeper slab and can harbor instabilities while more shallow locations move slowly toward stabilization.

WEATHER: In addition to being National Look on the Bright Side Day, today is the winter solstice, the first day of winter, and the shortest day of the year. With light winds and seasonable winter temperatures, there will be little weather-related movement in our avalanche danger either toward stability or instability. Yesterday was warm and sunny so there was likely some stabilization taking place in the upper layers of the snowpack. However, the sluff piles and slabs that we have concerns about tend to be deeper than the extent to which solar gain and warm temperature would have had a strong stabilizing effect.

SNOWPACK: Despite this year’s winter getting off to a good start, we are still looking at a very early season snowpack. In the ravines this is marked by intense spatial variability, broken and discontinuous snowfields, and large expanses of exposed rocks that should make you think about your travel route and its potential consequences in the event of a slide or fall. In Thursday’s avalanche cycle, multiple avalanches occurred in a wide variety of locations. Some were well outside of the “normal” avalanche paths, e.g. in Huntington to the east of North Gully and a small snow slope high above Diagonal. This should raise your hackles about any small pocket that didn’t release.

Solar gain and warmth yesterday likely had stabilizing effect, especially on slopes with a southerly aspect. However, we are reluctant to lower the ratings in many locations due to the depth of instabilities, particularly in sluff piles, may have prevented the solar energy from truly eliminating the weaknesses. There is a good chance you could be traveling on snow that has good stability, only to very quickly move into deeper slab with worse stability. This is where your ability to read the terrain and evaluate the snow becomes critical.

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 8:00 a.m. December 21, 2014. A new advisory will be issued tomorrow.

Jeff Lane, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2014-12-21