Avalanche Advisory for Tuesday, February 21, 2017

This advisory expires at Midnight.

 

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

AVALANCHE PROBLEM: Pockets of Wind Slab exist in our terrain and will provide the primary avalanche problem for the day. These pockets can be identified by their smooth appearance and are found in lee areas of NW winds. The likelihood of triggering these pockets is small and will decrease further through the day as settlement occurs. With clear skies and ample sunshine today, south facing aspects will soften and may present the problems with loose wet sluff management. This sluff can act like concrete, slow moving and hard to escape once entrained in it. Worth keeping in mind is the large wind slab that formed after our latest avalanche cycle last week. It will likely take more than a human to trigger this slab. The potential trigger out there today could be icefall. With temperatures warming, this possibility should be discussed.

WEATHER: After a week of snow and wind, this past weekend was a preview of the approaching spring. While temperatures remained largely below freezing up high, sunshine allowed snow to soften on south-facing aspects. Approximately an inch of snow on Sunday blew in on NW winds. High pressure today will create clear skies, mild winds, and temperatures into the mid-30sF. Clouds may develop in the afternoon along with a slight chance of mixed precipitation.

SNOWPACK: The snowpack encountered today will depend on what aspect the slope is facing. South facing slopes felt the effect of the sun over the past few days and are in the midst of a melt-freeze cycle, likely forming corn snow in areas today. SE slopes are beginning to metamorphose too, although these slopes have not felt as much sun and are just beginning the cycle. Skiers yesterday in the Sluice reported alternating turns on cold snow and sticky snow, highlighting the change that slope aspect can create. Keep in mind it is still February and the days are relatively short; many areas in Tuckerman and Huntington are still only seeing brief periods of escaping the shade of the neighboring ridges. East through north facing slopes have stayed cold, allowing the snow to stay dry in its various forms. Expect scoured old surface, firm sastrugi, and pockets of the snow from Sunday that has since formed wind slab. The wind slab will provide the softest cold snow but also harbors the greatest (albeit unlikely) instability of the day.

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., Tuesday, February 21, 2017. A new advisory will be issued tomorrow.

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

2017-02-21