Posted 8:10a.m., Tuesday, March 22, 2011
Tuckerman Ravine: The Center Bowl, Lip and Sluice have HIGH avalanche danger. Natural avalanches are likely and human-triggered avalanches are very likely. All other forecast areas in Tuckerman have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. The only exception to this rating is the Little Headwall which has Low avalanche danger. Natural and human-triggered avalanches are unlikely.
Huntington Ravine: All forecast areas in Huntington Ravine have CONSIDERABLE avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely.
This morning’s measurements below the ravines show that we picked up somewhere in the neighborhood of 4” (10cm) of new snow while the Observatory staff recorded about the same up top. Cold temperatures allowed snow to stay nice and dry but riming on the crystals has caused slightly higher densities than one might expect. Winds hung out of the S yesterday until around midnight when they made the quick transition to the W and then NW. Speeds ranged from 30-50mph (48-81kph) for most of this period though they dipped down after dark to less than 20mph (32kph) for a while before rising again in the early morning hours. This wind pattern primarily loaded slopes with a N aspect though E-facing aspects likely developed new windslab through cross-loading. Though little new snow is expected today the wind is going to be the key factor in the day’s elevated avalanche danger. As the day progresses we should see an increase in wind speeds with sustained speeds up to 60mph (97kph) and gusts that push even higher. These winds will originate from the NW and thus snow will be moved into the ravines from the summit cone, Alpine Garden and Bigelow Lawn. As this snow blows in it will be deposited on top of the thin layer of unconsolidated fluff that came in during the evening lull in wind speeds. Although this layer might not be easily discernable by eye or the occasional probing of the snowpack I would expect that stability tests would highlight this weakness within the new storm snow. Just make sure you’re not doing your stability tests out in one of the gullies! We expect visibility to remain limited today and our avalanche paths are all fairly well-developed for this point in the season. This means that avalanches have the potential to run fairly far including across the floors of both ravines. Areas in the direct lee of today’s winds, such as those rated as High, have the greatest likelihood of avalanche activity and their run-out paths extend across the regular access to most of the other forecast areas. Of the areas that are rated Considerable today there is a range of conditions. Some such as the Escape Hatch in Huntington are on the lower end of the rating with the primary concern being the potential for human-triggered slides. Its next-door neighbor South Gully is quite a bit higher in the Considerable range with a large portion of its start zone in the direct lee of forecasted winds. Be smart out there and don’t hesitate to grab one of the Snow Rangers if you have any questions.
- 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.
Justin Preisendorfer, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856