Avalanche Advisory for Tuesday, February 27, 2018

Huntington Ravine has MODERATE and LOW avalanche danger. Central, Pinnacle, Odell, South, and Escape Hatch Gullies have Moderate avalanche danger. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully to identify features of concern. North, Damnation, and Yale Gullies have Low avalanche danger. Watch for unstable snow on isolated terrain features.

Tuckerman Ravine has MODERATE avalanche danger. All forecast areas have Moderate avalanche danger. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully to identify features of concern. The Little Headwall is an open stream and is not rated.

AVALANCHE PROBLEM: Areas of wind slab exist across much of our terrain amid a more widespread refrozen surface of older snow. Size of this wind slab varies across Moderate-rated terrain and is distributed most widely in Central Gully in Huntington and Hillman’s Highway in Tuckerman. Today provides both an obvious and challenging avalanche problem to deal with for those seeking good turns. The new slab in which it is possible for you to trigger an avalanche is easy to see, appearing very white in contrast with the grey old surface. You can avoid the avalanche problem by avoiding travel on or below this visually apparent wind slab. That said, searching for good turns will lead you to travel on the avalanche problem, as the refrozen old surface will be far less than ideal for skiers and riders. Climbers will find good crampon purchase on the refrozen surface and likely be less tempted to travel on wind slab. This slick refrozen surface will easily allow a long sliding fall that most would struggle to arrest. If a stumble or even the smallest of avalanches causes you to lose your footing, you could take a long high-speed slide with potentially serious consequences. Take care, avoid falls and carefully assess consequence when choosing terrain.

WEATHER: Warmer, though below freezing temperatures, and W summit wind around 50 mph prevailed yesterday as skies trended toward clearing. We should have minimal cloud cover today with temperatures approaching 20F on the summit and remaining below freezing in our terrain. Westerly wind is forecast to increase through the day and ultimately gust to 80 mph this afternoon on the summit. A cold front arriving late tonight will bring back a snowy pattern to the mountain, with potential for several inches of new snow tomorrow and snowfall continuing into tomorrow night.

SNOWPACK: The wind slab that formed late Sunday, and into Monday morning, is our only stability concern at the present time. Our deeper snowpack has seen successive melt/freeze events, and the hard, refrozen surface on which our pockets of wind slab sit, does not hide deeper layers posing much avalanche concern. Significant wind transport over the last few days has created great variability in distribution and character of the new wind slab across our forecast area. Further, select aspects which saw greatest exposure to solar warming yesterday will hold a melt-freeze crust on the wind slab. As mentioned above, realize that the hunt for good skiing in these variable conditions will lead you to the avalanche problem and that there is a lot of icy, refrozen snow at the surface.

The John Sherburne Ski Trail holds a wide variety of conditions, including significant exposed ground, areas of water ice, thinly veiled rocks, and also some skiable snow. While mostly skiable it is certainly in challenging condition.

• 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 or Harvard Cabin.
• Posted 8:20 a.m., Tuesday, February 27, 2018. A new advisory will be issued tomorrow.

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