Avalanche Advisory for Sunday, February 12, 2017

This advisory expires at Midnight.

Huntington and Tuckerman Ravine have MODERATE avalanche danger today. All forecast areas have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully to identify features of concern. The only exception to this rating is the Little Headwall which has Low avalanche danger. Natural and human-triggered avalanches are unlikely there.

A backcountry avalanche watch is currently issued. A warning will likely go into effect tonight through midnight on Monday. Tomorrow, snow totals approaching 24” combined with strong winds will create widespread natural avalanche activity.

AVALANCHE PROBLEM: Loose-Dry avalanches will be the concern for the main part of the day today. As snow accumulates, the likelihood of these will increase. Areas of Wind Slab that formed on Saturday remain primarily on north and north-east facing aspects. If traveling in terrain today, be on the lookout for softer pockets that exist near terrain features. While these soft wind slabs were cracking underfoot yesterday but not propagating, a loose dry overloading this today could add enough weight to propagate a fracture. As darkness falls and the bulk of the storm arrives during the night, expect storm slab and wind slab to form, rapidly increasing avalanche danger.

WEATHER: High winds from the NW that topped the century mark on Friday have gradually decreased to a current 12mph from the south. Yesterday, just over 4” of light density snow fell on our terrain. Today, snow looks to pick up in intensity in the early afternoon. By dark today, we may see up to 6” of new snow with winds shifting to the SE and increasing to 50mph. No matter how you look at the models for the approaching storm, there is a lot of snow coming. By Tuesday morning, we should see around 20” with high winds moving even more snow in avalanche terrain.

SNOWPACK: Scoured 1” thick breakable crust along with pencil-hard wind slab is the predominant snow surface to start the day. In lee areas of SW winds, scattered, soft wind slab formed yesterday and is primarily in mid-elevations of our terrain. This new softer slab was up to two feet deep in places under the steepest terrain, but made of light-enough density snow that it would not prevent postholing into the crust beneath. As snow arrives today, sluff management will present problems, especially if the sluff entrains this soft slab. As winds increase at the end of the day and the intensity of snowfall increases, storm slab and wind slab will become widespread. Expect rapidly increasing avalanche danger around dark this evening.

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  8:25 a.m., Sunday, February 12, 2017. A new advisory will be issued tomorrow.

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