Avalanche Advisory for Friday, January 26, 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: The mountain received 2.5” of snow at the tail end of Tuesday’s low pressure system followed by strong winds from the west then north-west. Wind velocity was strong enough to scour the Alpine Garden above the ravines and deposit wind slab in our areas of concern. By and large, in good visibility, these wind slabs should not be difficult to avoid. In steep narrow gullies where route options are limited, venturing onto and triggering one of these slabs could result in a very nasty sliding fall on the icy bed surface. In the upper reaches of Left Gully and Chute, wind slab stretches wall to wall with no real option to avoid them. These wind slabs were poorly bonded to the ice crust beneath and sheared cleanly and easily. Be aware that low rated areas in our terrain may also be harboring these problematic wind slabs, though smaller in size with more options to avoid them altogether.

WEATHER:  Clear, cold and windy to start the day, with both temperature and wind hopefully moderating in the afternoon as the high pressure crests.  Current temperature at Hermit Lake is 3F and -9F on the summit.   Current summit wind is 62 mph from the NW.  Skies should remain clear for the forecast period with winds shifting west and diminishing to 20-35 mph by sunset. Summit temperatures will rise to the low teens.

SNOWPACK:  We had a great start to the season, but two warm rain events have reduced the snowpack to a mostly solid frozen mass. During field observations yesterday, it was clear that much of the snowpack is hard, refrozen snow from previous rain events, however there are many pockets of wind slab varying in size and depth scattered around. We found these slabs to be 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 cold temperatures overnight only weakened this bond to the icy crust.

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 7:15 a.m., Friday, January 26, 2018. A new advisory will be issued tomorrow.

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

2018-1-26