Avalanche Advisory for Thursday, February 16, 2017

This advisory expires at Midnight.

Huntington Ravine and Tuckerman Ravine will have HIGH avalanche danger today. All forecast areas will have HIGH avalanche danger. Natural avalanches are likely and human-triggered avalanches are very likely. Very dangerous avalanche conditions exist. Travel in avalanche terrain is not recommended. The only exception to this rating is the Little Headwall which may rise to Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible there.

Very dangerous avalanche conditions will exist today. Avoid all avalanche terrain later today as wind speeds begin to increase. Large avalanches in many areas will be likely.

AVALANCHE PROBLEM: This morning, there is Considerable danger of Wind Slab and Dry Loose avalanches from 8” of new snow last night. Though this new snow was deposited on generally light winds, some gusty conditions mid-storm may have created a cohesive slab in some areas. Much larger and more dangerous Wind Slab avalanches will be likely this afternoon as wind from the northwest ramps up. These slabs will release naturally and most likely run far into flat areas like the floor of Tuckerman Ravine and the wooded areas in Huntington. Our avalanche paths have grown very large in the past week. The size of these slopes, the available new snow, and the high winds have set the stage for very dangerous avalanche conditions today. Travel in avalanche terrain is not recommended.

WEATHER: 7.5” (19cm) at Harvard Cabin and 8” (20.5cm) at Hermit Lake (.95 SWE) of new snow fell in the past 24 hours on predominately light and variable winds. SSE gusts to 47mph occurred yesterday afternoon for a couple hours. The main weather factor driving our avalanche danger rating today will be the steadily increasing wind from the north which will shift to the northwest and blow at speeds that will easily load new snow into our start zones. Warm, moist air hanging around the North Country should provide ample moisture for upslope snowfall in the 2-4” range. This will challenge visibility and add to the new load of snow.

SNOWPACK: Our active weather pattern has grown the avalanche terrain in our forecast areas to near epic proportions. Avalanche activity from the 20”+ nor’easter 4 days ago deposited debris darn close to the maximum extent in most of our avalanche paths. Earlier avalanche activity from the Center Bowl ripped up the old ice crust and accessed some of the sleet deposits from the mixed precipitation storm a couple of weeks ago. Wind slabs were found to be on the softer side in some locations on Tuesday, so the possibility exists that today’s new large wind slabs will step down into these older slabs and add to the problem. If you are attempting to poke into the terrain this morning before the wind ramps up, I would definitely be on the lookout for a cohesive layer within this new snow. Gusty mid-storm winds could have created enough cohesion to cause propagation in otherwise loose snow. Crossing avalanche paths in our forecast area and entering Tuckerman or Huntington Ravine will put you in the crosshairs for multiple avalanche paths today.

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., Thursday, February 16, 2017. A new advisory will be issued tomorrow.

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