Avalanche Advisory for Saturday, February 22, 2014

This advisory expires at 12:00 midnight.

All forecast areas of Tuckerman Ravine have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully. There are two exceptions to this rating: the Lower Snowfields and Little Headwall which have Low avalanche danger. Natural and human triggered avalanches are unlikely in these areas.

Huntington Ravine has Moderate and Low avalanche danger. Central, Pinnacle, Odell, South, and Escape Hatch have Moderate danger. Natural avalanches are unlikely and human triggered avalanches are possible. North, Damnation, and Yale gullies have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

AVALANCHE PROBLEMS: Two problems should be on your mind today, wind slab and deeper wind slab. The interaction between these two problems and a crust layer sandwiched between them is where the real story lies. The take home points for today are 1) a freezing rain crust developed midday yesterday, 2) deeper instabilities existed before the crust was formed, 3) the crust will help stabilize slabs beneath it, but fails to eliminate all stability problems, and 4) new wind loading and sluffing may create additional slabs on top of this crust in specific terrain features.

WEATHER: The big weather-related player is yesterday’s crust. I feel bad for the first skiers on the Sherburne today. Hopefully they’re wearing shin guards because the crust here at Hermit Lake is at least a half inch thick and breakable underfoot. The lower part of the ravines only barely and briefly reached above the freezing point for temperatures, so the rain was able to freeze on the snow surface instead of penetrating into the snowpack.

It’s hard to believe that clouds will engulf the summits later this afternoon, because right now it’s about as clear as it gets. Winds are currently finding snow to blow around, which we believe is due to crust being ripped up above treeline, exposing underlying snow to fairly strong winds. Loading may increase as strong gusts above treeline expose more snow through the day; I expect some areas in the ravines will be scoured down to the crust but not below. We’ve had some decent snowfalls, 12.5” (32cm) in the last four days, though very strong winds yesterday and Thursday have already affected this snow to some extent.

SNOWPACK: This freezing rain crust will do some good for adding strength to any slabs that are underneath, however, at the same time it will provide a slick bed surface to any new loading that lands on top of it. Expect varying degrees of hard slab under the crust with generally good stability. But remember that the snowpack is thin right now and potential weak points are only shallowly buried. Taken all together, I’d say we’re in the Moderate range with some locations having better stability than others.

Please remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is 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 USFS Snow Rangers, the AMC at the Pinkham Notch Visitors Center, or the caretakers at Hermit Lake or the Harvard Cabin
  • Posted 8:30a.m., February 22, 2014. A new advisory will be issued tomorrow.

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

2014-02-22 Print Friendly