Avalanche Advisory for Tuesday, March 29, 2016

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Considerable and Moderate avalanche danger. The Sluice, Lip, Center Bowl, and Chute have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. All other areas have Moderate avalanche danger.

All forecast areas of Huntington Ravine have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible.

AVALANCHE PROBLEM: Wind slab is the avalanche problem today. Hard wind slab may be building today in many areas due to very strong winds and overnight snowfall. The greatest concerns are in strongly sheltered lee areas which are rated Considerable today. Hard slabs are generally very strong, very dense, and run long distances when they release. This shifts the focus from human-triggering to natural avalanches. Venturing into the lower reaches of either ravine may put you within reach of a naturally-triggered slide.

WEATHER: Yesterday the mountain was subjected to yet another March rain, the fourth time this month. Precipitation transitioned to snow in the early evening, and snow continued to fall until the predawn hours, bringing 3.5″ of snow to the summit by the 7:50 a.m. measurement. W and WNW winds rose steadily during the snowfall, peaking at well over 100mph early this morning. Currently, we are experiencing what is likely the strongest winds we’ll see, as they are forecast to gradually decline throughout the day. By nightfall, summit winds should still be strong at 60-80mph. Upslope snow showers can be expected this morning, adding a little more to the totals before the air mass completely dries out. Blowing snow should be expected throughout the day.

SNOWPACK: With yesterday’s rain and overnight freezing temperatures, the underlying snowpack has stabilized to the point where today’s concerns are strongly focused on any slabs building at the surface. Winds gusting 110-130mph this morning lead us to suspect that none of the new snow is sticking in many of the forecast areas. This is most likely to be true in most of Huntington as well as Left Gully and Hillman’s Highway. However, as winds decrease today to speeds where snow can actually stick to the slopes, new slabs may develop if there is still a sufficient supply of snow in the alpine zone for loading to continue. The areas rated Considerable also may have been scoured or pounded into submission by the winds, but given their sheltered nature and being more protected from the winds, they are more likely to have developed deeper hard slabs. If this scenario is playing out, you will find strong hard snow that might have great stability relative to the impacts a person can generate, but the increasing weight of the slab caused by ongoing loading may be enough to trigger a spontaneous natural avalanche. This is the primary concern today, and it’s possible that it’s not actually a problem, but until we can get eyes and hands on the snow, making conservative decision is prudent.

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 8:10 a.m., Tuesday, March 29, 2016. A new advisory will be issued tomorrow.

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