Avalanche Advisory for Sunday, February 4, 2018

Huntington and Tuckerman Ravine will have CONSIDERABLE avalanche danger. Dangerous avalanche conditions will develop today. Natural avalanches will be possible and human triggered avalanches likely. Cautious route finding and conservative decision making are essential. In Tuckerman Ravine, the Little Headwall is not quite filled in enough to ski or ride.

AVALANCHE PROBLEM: Wind slabs will begin to develop early this afternoon as snow begins to accumulate at higher elevations. Southwest winds will blow in the 50 mph range at the ridgetops and build wind slabs which will be increasingly sensitive to human-triggers and prone to natural avalanches. Dry loose sluffs will complicate matters by challenging travel and adding to the load on wind slabs, particularly on approaches to climbs and beneath buttresses and steep pitches of ice. Be aware that cross-loading of features due to localized wind patterns is as significant a problem as big slopes in the direct lee of a southwest wind. As an example, Central Gully faces east but is likely to be first to become hazardous today due to drifting across the buttress above and a steep smooth bed surface. If you are reading this anywhere other than at the base of a climb in Huntington, you are most likely starting too late to avoid being in the cross hairs of today’s avalanche hazard.

WEATHER:  Moist southwest flow is pushing into the region this morning, bringing snow to the higher elevations. Our forecast area will see all snow from this system and could pick up 12-14” by the time it is over early tomorrow. The current temperature is a balmy 12F on the summit with 65 mph winds from the southwest. The temperature has rebounded from a low yesterday of -13F to 17F at Hermit Lake with light snow falling. Anticipate up to 6” or more of new snow by nightfall. Remember that slabs can easily grow 5-10 times thicker than the snowfall with our fetch and forecasted wind speed.

SNOWPACK: Some field observations yesterday in decent visibility revealed that new snow had built firm and stubborn wind slabs across the terrain. They were likely of producing only a small avalanche in most places due to their discontinuous nature across the terrain. Sluice through Chute and Central were wall to wall with not enough old surface to skirt the finger and pencil density slabs over softer (4F) layer. One noteworthy feature to keep in mind going forward is that those slabs from the 6” or so that was deposited Wednesday and Thursday smoothed over water drainage channels and other features that broke up the old surface. This will setup our surface to allow new avalanches to propagate wider and larger in their respective paths. Expect larger avalanches overnight and tomorrow.

The Sherburne Ski Trail is starting the day in a very icy state with refrozen crust and pure water ice. Ski it late today or better yet wait till more snow covers it tonight. There are nasty water erosion features and rocks embedded in the ice that need more coverage.

Please Remember:
• 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 8:00 a.m., Sunday, February 4, 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

2018-2-4