Posted 8:00a.m., Sunday, April 3, 2011
Tuckerman Ravine: The Sluice, Lip, and Center Bowl have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Lobster Claw, Right Gully, the Chute, Left Gully, Hillman’s Highway, and the Lower Snowfields have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The Little Headwall has Low avalanche danger. Natural and human triggered avalanches are unlikely.
Huntington Ravine: North, Damnation, and Yale have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. All other areas have Low avalanche danger. Natural and human triggered avalanches are unlikely, however, watch for unstable snow on isolated terrain features.
The storm system that embraced the mountain over the past couple days has finally cleared out, and bluebird skies are allowing us numerous visual clues as to what took place yesterday under the thick cover of clouds and blowing snow. It’s the aftermath of the storm that provides today’s avalanche concerns. For the most part, the greatest concern comes in the way of human triggered avalanches. Three forecast areas in Tuckerman are rated Considerable today; these areas have a substantial amount of new windslab due to being protected from the NW winds. Yesterday’s winds were more gentle on these slopes than others, which results in relatively softer slabs and a greater potential for a person to trigger an avalanche here than in locations more exposed to strong winds. To further the case for Considerable, there is still low drifting snow blowing around in areas such as the Tuckerman headwall, the top of Hillman’s, and the Lion Head ridge. It’s not uncommon to have naturally triggered avalanches result from this type of windloading on a bluebird day. We expect this to subside in the afternoon, but until then we aren’t ruling out natural avalanche potential.
Locations posted at Moderate today have a wide variety of conditions. In some areas you’ll find hard wind effected snow or even wind scouring while in other locations you’ll find softer areas of fresh windslab. For example Left Gully has a wind scoured upper section but new snow has blown into the narrows and below. The more sensitive new slabs are most likely to be found on slopes with their backs to the NW winds, such as the climbers’ left sides of Lobster Claw and Right Gully and the top climbers’ right side of Hillman’s. Also be wary of transition areas between different conditions. This is often where unstable slabs can be thin and easy to trigger while having the potential to propagate out into deeper slabs. The last few weeks have changed the face of Tuckerman Ravine. Slopes are larger and more connected to one another than they have been all season, and runout paths are fully developed. You should think not only about stability directly underfoot, but also of what is going around you in adjacent areas.
In Huntington, the northern gullies all have clear evidence of avalanche activity, and they also have the largest stability problems. In addition to potentially unstable snow in the gullies themselves, the steep approaches to the ice may also have problems to watch out for. In the areas posted at Low, you’ll also want to be mindful of isolated pockets. There is currently spindrifting going on in the tops of most gullies that may be creating relatively small areas of windslab. The Harvard Cabin is now closed for the season. Camping in the Cutler River Drainage is allowed only at Hermit Lake Shelters.
- 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 the Harvard Cabin.
- This advisory expires at midnight. A new advisory will be issued tomorrow
Jeff Lane, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856