Avalanche Advisory for Saturday, April 9, 2016

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has LOW and MODERATE avalanche danger. The Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Heightened avalanche conditions exist in certain terrain features within these forecast areas. Evaluate snow and terrain carefully to identify specific areas of concern. Right Gully, Left Gully, and Hillman’s Highway have Low avalanche danger.  Natural and human-triggered avalanches are unlikely except in isolated pockets. The Lobster Claw, Little Headwall and Lower Snowfields are not posted due to lack of snow.

Huntington Ravine is under a General Bulletin for the remainder of the season. 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: Today’s avalanche problem is new Wind Slab. Over the past two days the summit has had just short of 6″ of new snow.  3.5″ fell in the past 24 hours, most of which fell last night on a W wind between 40-60mph.  Many new winds slabs are mixed with old surface although some areas have greater human trigger potential than others.  See Snowpack section below for details.

WEATHER: Temperatures fell to 3F last night on the summit. Mercury should rebound to about 12-13F before falling again to -5F tonight.  Winds have abated from a peak of 60mph to about 35 but should increase again this afternoon gusting to 50mph.   Expect true winter conditions today with appropriate winter mountaineering clothing. Consider a conservative timetable for your day to avoid the very cold air moving in late today and tonight.

SNOWPACK: The copious rain from Wednesday, which soaked deep into the snowpack, has refrozen due to very cold air making for generally very hard slick conditions.  Since that rain we have received about 6″ of snow,  3.5″ falling yesterday and last night.  This snowfall and overnight wind gave the Ravine a nice skim coat of white this morning, but has also created new pockets of slab over the hard slick older grey surface. Some of these new areas of wind slab harbor more instability than others based or their size, depth, and slope angle.  Based on these factors we have the most concern in the Lip, high in the left Center Bowl, and over into the Chute. Other areas posted at Moderate have areas of concern, but are peppered with more visible old surface. The lower Center Bowl and the Sluice are two example of this. Overall, some of the new wind slabs could bury a person but it’s more likely that a human-triggered avalanche would take someone for a very long ride on the icy bed surface through rocks, brush, and over cliffs. Based on the hard old surface underfoot in many locations, expect travel to be difficult and a slip has a high potential for a long devastating fall. Besides avalanche hazard these are very important points to remember today:

  • 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. However, arresting a fall on a steep icy slope can be practically impossible even with an ice axe.
  • Crevasses, moats and waterfall holes – Warm water flowing under the snow pack creates holes and thin spots in surface that are deep enough to injure or kill you. New snow can drift and obscure the openings.

The Sherburne Ski Trail is now closed one third of the way down from Hermit Lake. Expect water ice under a dusting of new snow.

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 8:10 a.m., Saturday, April 9, 2016. A new advisory will be issued tomorrow.

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