Avalanche Advisory for Saturday, January 27, 2018

Huntington Ravine has LOW avalanche danger. All forecast areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.

Tuckerman Ravine has MODERATE and LOW avalanche danger. Sluice, Lip, Center Bowl, Chute and Left Gully have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully. All other forecast areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.  The Little Headwall is mostly open water or waterfall ice and not rated.

AVALANCHE PROBLEM: Lingering wind slabs are the primary avalanche problem today. These slabs are poorly bonded to the icy, rock hard snowpack though are limited in size and distribution. Today, these areas of wind slab will warm for the first time and likely become more sensitive to human triggers as they weaken. Ultimately the heating will bring some stability to these slabs but not before passing through a period of less stability. Evaluate snow for signs of instability and bonding to bed surface, especially since even a small avalanche or fall can have serious consequences on our icy slopes. Larger areas of wind slab have a moderate rating due to the possibility of a human-triggered avalanche.

WEATHER:  A warming trend began last night with southwest flow and warming temperatures. After two days of below zero temperatures, the summit has reached 23F and will warm to the upper 20’s today before a cold front brings moisture to the area. It’s likely that our forecast area will see a mix of wet snow and rain. Less than an inch of snow and a tenth of an inch of rain will fall starting around dark. Temperatures will fall tonight with upslope snowfall continuing through the day tomorrow. WSW winds today will blow in the 40 mph range today, slowly ramping up through the day.

SNOWPACK:  December brought over 8’ of snow to the summit, but two warm rain events have reduced the snowpack to a mostly solid frozen mass with drainage channels in the surface, glide cracks and a slick icy surface. During field observations Wednesday, much of the snowpack was found to be a hard, refrozen snow from previous rain events, but with many pockets of wind slab varying in size and depth scattered around. These slabs were firm (finger to pencil) and poorly bonded to the ice crust below failing on a weak layer of snow (four finger) at the bed surface. It’s likely that the continued cold temperatures since that time only weakened this bond to the icy crust. Limited settlement may have occurred yesterday on aspects with strong solar gain but not enough to feel confident that human-triggered avalanches are now unlikely. The old gray, icy surface remains a safer place to evaluate the new snow as long as you’re wearing crampons, carrying an ice axe and moving carefully in the terrain.

The large wet avalanche in the Lip is slowly starting to fill in, but the hole in the snowpack and 20’ crown face is far from gone.  Skiing has been better this year for sure, but snow and ice climbs are in great shape. The Sherburne Ski Trail is a refrozen mess and best left for the most hardy and desperate of skiers.

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This bulletin 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 Harvard Cabin.
• Posted 7:20 a.m., Saturday, January 27, 2018. A new advisory will be issued tomorrow.

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

2018-1-27