Avalanche Advisory for Tuesday, December 20, 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: Today’s avalanche problem will be Wind Slab. These will likely be small, tucked under and behind terrain features, and easy to identify. However, with an icy surface underneath, even a small avalanche can create a significant hazard. This is due to the fact self-arresting on the slick surface will be next to impossible. Long, sliding falls are the main concern today. Crampons and an ice axe will be crucial to safe travel.

WEATHER: Unseasonably warm temperatures on Saturday night into Sunday brought along a half inch of rain. Following this, temperatures bottomed out at -16F and have now rebounded to more a more normal temperature of 7F. On Monday, the Summit recorded 0.2” of snow. Today will be clear with west winds starting at 30mph and increasing to 75mph through the day and night. We may see a dusting of snow tonight and possibly again tomorrow.

SNOWPACK: The warming and rain event allowed our snowpack to hit the reset button in terms of stability. While weak layers remain further down in the snowpack, it will be highly unlikely to impact them due to the bridging strength of the melt/freeze crust now bridging the surface of the snow. The dusting of snow on Monday was subjected to strong winds. Expect small, isolated pockets of newly formed wind slab to exist in lee areas. On previously wind scoured surfaces or impacted trails, the crusty surface will allow quick travel, provided you have crampons to bite into the snow and ice. Long, sliding falls are a distinct possibility today on steep surfaces. Even lower-angled surfaces can cause out-of-control slides for the unprepared. Below treeline and deep in the woods, this crust will provide postholing conditions that your shins will not let you forget. It may be a good day to rethink your bushwhack to Isolation.

The Lion Head Winter Route is open and the most direct route to the summit from the east side of the mountain. The Tuckerman Ravine Trail bridge is completed enough to allow traffic, so you can avoid the detour. Please be careful of construction debris near crossover 7 on the Sherburne Trail and some snow machine and snow tractor traffic as some final work for the season continues. 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 8:00 a.m., Tuesday, December 20, 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

2016-12-20