Avalanche Advisory for Wednesday, April 13, 2016

This advisory expires at midnight.

Tuckerman Ravine has LOW avalanche danger.  Natural and human triggered avalanches are unlikely except in isolated terrain features. Lobster Claw, Lower Snowfields and the Little Headwall are not posted due to lack of snow.

Huntington Ravine is under a General Bulletin. You will need to do your own snow stability assessments when traveling in avalanche terrain in Huntington. A danger of falling ice exists, and will persist until it all comes down.

AVALANCHE PROBLEM: Yesterday’s primary avalanche problem of Wet Slab, due to warm temperatures and +/- 0.5″ rain on Wind Slab, dissipated quickly overnight as temperatures fell.  The snowpack is freezing from the surface down increasing strength, dramatically reducing avalanche problems, and giving the primary mountain hazard concerns over to falling ice, crevasses, and hard steep surface conditions.

WEATHER: Summit temperatures yesterday rose to 35 F with almost 0.5″ of rain falling followed by a brief period of scant snow.  Avalanche terrain in Tuckerman shot into the high 40’sF.  As the front passed on Tuesday morning temperatures dropped off rapidly into the low teens, currently hovering around 9F on the summit.  High pressure will become established producing fine sunny days for the extended forecast.

SNOWPACK: New wind slabs that established over the weekend, and again on Monday, transformed yesterday due to warm air and steady spitting rain adding up to 0.5″ of liquid.  Rainfall amounts mixed with melt water to penetrate new surface wind slab instabilities to create wet slab problems yesterday.  As the mercury fell off overnight, and precipitation ended, free water began refreezing from the surface down decreasing our instability concerns. Rapid settlement and the freezing of liquid water increased the snowpack strength dramatically overnight.  The frozen crust thickness will continue to increase through the morning and then slow as the solar gain increases especially on SE and S facing slopes, such as the Sluice and Right Gully.  With clear cold nights, low winds and clear sunny days in the extended forecast the snowpack will be interesting to watch for snow science aficionados. Areas where soft slab existed may re-crystallize and go through some winter like faceting, while the old dense grey surfaces will remain hard and change very little.

  • Long sliding falls – Crampons, an ice ax, and the experience and skills to use them effectively are required to travel safely in steep terrain. Snowshoes and microspikes are absolutely no substitute.
  • Crevasses, moats, and waterfall holes – Water flowing under the snow pack creates holes, glide cracks (crevasses) and thin spots that are deep enough for grave consequences. The climber’s right side of the Bowl, near and under “The Lip”, harbor the most amount of holes.
  • Falling ice – The best thing you can do is reduce your exposure by limiting the time spent downslope from frozen waterfalls. Falling ice chunks can move with surprising speed and follow unpredictable trajectories. Expect this hazard to increase each day as sun warms the Ravine.  Icefall Rocks (Lunch Rocks) is a historically notorious bad place to sit as many very bad outcomes have occurred there.  It is a shooting ice gallery from the Headwall and the Sluice.

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.
  • Posted 6:35 a.m., Wednesday, April 13, 2016. A new advisory will be issued tomorrow.

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