Avalanche Advisory for Thursday, January 18, 2018

Huntington Ravine has MODERATE avalanche danger. All forecast areas have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully.

Tuckerman Ravine has MODERATE and LOW avalanche danger. All forecast areas have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully. Lobster Claw, Right Gully and Lower Snowfields have Low avalanche danger. Watch for unstable snow on isolated terrain features like the top of Lobster Claw and the choke of Right Gully.  The Little Headwall is mostly open water or a frozen waterfall.


AVALANCHE PROBLEM: Wind slab may develop today when gusty winds blow available snow into avalanche terrain. Limited amounts of new snow in the past 48 hours, along with moderate winds should limit wind slab development but stay tuned in to what’s happening at the ridge tops. As of this writing, upper start zones are mostly old surface with new snow generally pushed down to midslope through wind action or sluffing. Human triggering of these wind slabs is possible today though the resulting avalanche would be on the smaller side. Of equal or greater concern to avalanche issues today is the slide-for-life conditions camouflaged by the thin blanket of new snow. Any stumble or fall is likely to have serious consequences in any steep terrain due to the hard surface. Roping up early and not falling are your best protection on steep slopes.


WEATHER: In the past 24 hours, just 2” of new snow fell on the summit while 3cm (1.25”) fell at Hermit Lake. Roughly 3” of light density snow is lingering in the alpine fetch zone upwind of our terrain since the recent storm passed to our south. Yesterday, peak wind speed on the summit was just 42 mph out of the west though a 70 mph reading was taken at 7:00am this morning with winds expected to shift to the northwest. Today’s wind forecast holds the possibility for some transport of this snow but between moderate wind speeds, calming to the 40 mph range, and lots of nooks and crannies in the fetch to shelter the snow, sustained wind transport seems unlikely. Gusts from the northwest may move some snow around and create our primary avalanche concern today. Temperatures under clear skies will be in the 10-15F range on the summit through the day. Good visibility should remain through the day.


SNOWPACK: As mentioned above, the snowpack is hard. A prolonged warming spell with rain late last week turned the upper portion of the snowpack into a knife hardness crust. The recent warmup ended with a period of freezing rain that glazed trees and snow surfaces at our elevation with ice. While weaker snow exists deeper in the snowpack, it is not at all a player in current avalanche concerns. The blown out portion of the Lip below the Tuckerman Ravine Trail and the hard, refrozen debris pile remain visible in Tucks. Crampons and sure footedness are needed for travel any steep terrain today.

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 8:00 a.m., Thursday, January 18, 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