Avalanche Advisory for Wednesday, January 17, 2018

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger. Central Gully has Considerable avalanche danger. Dangerous avalanche conditions exist. Cautious route-finding, conservative decision-making are essential today. All other forecast areas have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully.

Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. Lip, Center Bowl, Chute, Left and Hillmans Highway have Considerable avalanche danger. Dangerous avalanche conditions exist. Cautious route-finding, conservative decision-making are essential today. Lobster Claw and Right Gully have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully. Lower Snowfields has Low avalanche danger due to lack of snowcover.  The Little Headwall is mostly open water or waterfall ice. 

AVALANCHE PROBLEM: Wind slab may develop this afternoon as light density snow is blown on westerly and southwesterly winds. Though on the smaller side, these avalanches will likely be sensitive to human triggers. Dry loose avalanches or sluffs are also likely to occur today and could entrain enough snow to knock you off a stance in steep terrain. Both avalanche types are developing on top of a hard, icy crust that will be not only a slippery bed surface but will also create slide-for-life conditions. Due to the light snowfall today, the size and distribution of these avalanche types will grow through the day and depend on receiving the forecast amount of snow. The most imminent threat that will remain constant throughout the day is the icy crust and the potential for a long sliding fall into rocks, stout bushes and holes melted into the snowpack.

WEATHER: Light snow continues this morning after about 2” of snow fell on the summit in the past 24 hours. Down lower at Hermit Lake, 3.5 cm of snow was recorded on the storm board at 6:30 this morning. West-southwest winds are currently light at around 25 mph but are expected to increase later in the day. 2-4” more snow is forecast today with 2” more tonight. The size and distribution of the wind slab avalanche problem depends upon the today’s snowfall totals and wind speeds. Timing of the increase in wind speeds later in the day is unclear, though a minor increase will disproportionately increase avalanche danger level. Anticipate low visibility today due to summit fog and snow.

SNOWPACK: As mentioned above, our snowpack is hard. A prolonged warming spell with rain turned the upper portion of the snowpack into a knife hardness crust with the bridging power of structural steel. 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 any instabilities developing today. The blown out portion of the Lip and the hard, refrozen debris pile remain dominant features in Tucks. The recent rain and return of cold temperatures has been a boon to ice climbers. The Sherburne Ski Trail remains an icy mess, complete with a wall-to-wall field of frozen boot tracks in one section.  It will likely need more than today’s snowfall to create softer snow conditions. Crampons are needed for 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 8:15 a.m., Wednesday, January 17, 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

2018-1-17