Avalanche Advisory for Sunday, March 29, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Considerable, Moderate, and Low avalanche danger. Dangerous avalanche conditions exist. The Lip, Center Bowl, and Chute have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. The Sluice and Lower Snowfields have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Lobster Claw, Right Gully, Left Gully, and Hillman’s Highway, and the Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

Huntington Ravine has Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

AVALANCHE PROBLEM: Wind slabs are the primary avalanche threat today. The main driver behind the Considerable rating for some areas is the low drifting snow currently cascading down steep slopes. This slow loading has caused good-sized avalanches in the past, even on bluebird days like today. It is taking place in the Sluice as well, though as a slightly lesser rate. The Lower Snowfields contains snow with varying levels of stability. I expect the worst to be tight under the rock buttresses. Left Gully and Hillman’s have pockets of new snow loaded into isolated terrain features. Although posted at Low, they may contain unstable snow capable of producing an avalanche. It ain’t spring yet, folks, regardless of what the calendar says.

WEATHER: Blue skies will dominate today, but it will feel more like a nice day in February than the end of March. Expect temperatures below normal. Even south-facing slopes may not get enough heat to moisten the uppermost snow. Westerly winds around 30-40mph will have two noticeable effects. One is to generate additional wind loading, particularly low drifting snow in the center of Tuckerman. The other is to suck the heat away from the snow in south facing slopes, making it harder for the sun to soften the surface. Over the last four days, Mt. Washington has received about 7” of new light density snow, which is at the center of our avalanche concerns.

SNOWPACK: I wrestled with the ratings for Tuckerman today and decided on the higher rating of Considerable for locations where there currently is snow drifting down over the headwall. Today would not be the first time I’ve seen a seemingly small amount of loading trigger an avalanche. I’ll caution you all that as long as this is going on, you will want to be extra cautious. This means that even going into the floor of Tuckerman to access a Low rated area will put you at risk. If it shuts off completely, we’ll be left with a human trigger problem rather than a natural trigger problem. Although this isn’t ideal for recreation, it’s more manageable.

In Lobster, Right Gully, Left Gully, and Hillman’s, the majority of the surface snow is old and stable. However, there are locations where you may find unstable snow, such as the skiers’ left side of Left Gully or hard on the skiers’ left side of Hillman’s. Other examples may exist, too. You’ll need to be alert for these pockets, assess their stability, and determine whether or not you want to pass through them. You may also need to make a decision whether or not you want to be below someone who is making a similar decision!

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 8:23 a.m. Sunday, March 29, 2015. A new advisory will be issued tomorrow.

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