Avalanche Advisory for Tuesday, December 27, 2016

This advisory expires at midnight.

All forecast areas in Huntington and Tuckerman Ravine have LOW avalanche danger. Natural and human-triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

AVALANCHE PROBLEM: This morning, the avalanche problem will be Wet Slabs. The primary areas of concern would be the wind slab that formed in lee areas and under terrain features over the past weekend as these transition to wet slabs. Notoriously hard to predict, water may percolate lower into the snowpack and lubricate a layer farther down in the snowpack. Peak instability for wet slabs may already have passed as rain is no longer falling and temperatures begin their descent. As the snowpack freezes, beware of the potential for long, sliding falls. We may receive up to 2” of snow as the day progresses. Wind Slabs will develop, although depending on what time they form, they may bond well to the freezing snowpack.

WEATHER: Around dark last night, temperatures jumped to above freezing. Throughout the night, light rain, freezing rain, and ice pellets fell, delivering 0.26” of water. Today, strong W shifting NW winds have already reached the century mark and will linger there before decreasing to t the 70mph range by nightfall. With temperatures dropping today, and moisture lingering from the passing low pressure system, we may see up to 2” of upslope snow today and another 2” tonight.

SNOWPACK: Seven inches of snow fell since the previous melt/freeze cycle on December 17th and 18th. Strong winds over the past week scoured much of the terrain and left firm, well-bonded wind slabs in other areas. These wind slabs were not reactive in tests; they produced Q3 shears and did not propagate during ECTs. Rain last night soaked these slabs and old surface. As the temperatures drop, be on the lookout for hard icy surfaces to abound. Upslope snow showers will arrive later today on prime loading wind speeds, but I expect this snow to bond well to a simultaneously freezing surface. That being said, if we see the upper end of 4” today and tonight, beware of wind slabs forming quickly and be prepared to evaluate terrain with care if on the mountain early tomorrow.

The Lion Head Winter Route is open and the most direct route to the summit from the east side of the mountain. The bridge that is still under construction on Tuckerman Ravine Trail now allows traffic making this the preferred hiking route to gain elevation from Pinkham. Please be careful of construction debris near the top crossover when descending the Sherburne Trail and be on the lookout for heavy equipment as work continues.

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 8:15 a.m., Monday, December 26, 2016. A new advisory will be issued tomorrow.

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