Avalanche Advisory for Tuesday, December 16, 2014

This advisory expires tonight at 12:00 midnight.

All forecast areas of Tuckerman and Huntington Ravine have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features which may be capable of producing small avalanches.

AVALANCHE PROBLEM: Today’s avalanche problems will be any lingering pockets of wind slab or small wet slabs, depending on how quickly and how far temperatures drop during the day today. Low danger means conditions are generally safe, but it includes the possibility for unstable snow in isolated terrain features or in extreme terrain. In the current early season snowpack, pretty much all the snowfields except for a few can be considered “isolated terrain features” or “extreme terrain.” Wind slabs that developed this past Sunday have had time to stabilize, but I won’t rule out the potential for some instabilities to still be found out there, particularly in areas such as the Lip, Center Bowl, or Central Gully.

WEATHER: Yesterday the Mt. Washington Observatory recorded a max temperature of 41 degrees F (5C) and stayed above freezing for most of day and overnight. Temperatures at Pinkham Notch were down below freezing during this same period. Today we are expecting temperatures to drop slightly at the upper elevations. Increasing clouds will foreshadow a weather system moving in later tonight and sticking around until early Thursday. Keep your eyes on the summits weather forecasts if you are planning a trip for Wednesday or Thursday.

SNOWPACK: A prominent player in the snowpack discussion today is the elevation of the warm/cold line and, more importantly, just how warm the snowpack in the ravines in the last 24 hours. In this case, I would expect that warmth entering the snowpack has worked toward stabilization of previously existing wind slabs. If these became very warm and saturated wet, then the trend might have worked in the opposite direction as there would be a wet slab sitting on top of an ice crust or in some locations plain water ice, hence the discussion about the potential for pockets of unstable slab in isolated terrain features. I don’t want to get too bogged down in the nuances of warmth on snow, because I’m hopeful that falling temperatures will continue to strengthen the snowpack to where we will sit solidly in Low danger before long. Until lock-up happens, you should expect to find generally good stability with the potential for some small unstable slabs.

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 7:50 a.m. December 16, 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

2014-12-16