This advisory expires at Midnight, Thursday 2-14-2013
Tuckerman Ravine has LOW and MODERATE avalanche danger. Hillman’s Highway, Lower Snowfields, the Little Headwall and Lobster Claw have Low avalanche danger. Natural and human triggered avalanches are unlikely. Right Gully, Sluice, Lip, Center Headwall, Chute and Left Gully have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully to identify features of concern.
Huntington Ravine has LOW and MODERATE avalanche danger. Escape Hatch has Low avalanche danger. Natural and human triggered avalanches are unlikely. All other forecasted gullies have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.
Time and physical processes have brought slow stabilization to the windloaded areas of both ravines. A wide variety of surface conditions exist so climbers and skiers planning a trip into the ravines should be prepared for anything from hard wind slab, bullet hard rain crust as well as areas of soft snow thrown in to make things more interesting. Most areas rated at Moderate are at the low end of the rating so arm yourself with key weather data and exercise sound travel skills today.
Over the past three of days the summit received 5.5” (13 cm) of new snow on winds coming from the SW to the NW with the majority of the snow (5.1″) falling on Monday and Tuesday. Winds abated through the day yesterday, with speeds dropping steadily from the 50’s mph 24 hours ago to around 25 mph by lunchtime yesterday and further into the teen’s mph (15-30 kph)where they have remained for the last 12 hours. The low windspeeds have laid a veneer of new snow which is obscuring many of the visual clues that indicate the texture and, by extension, the travel qualities of the snow pack. Opportunities to visually assess the snow will increase as the clouds lift through the day but expect a mix of riding and skiing qualities top to bottom in any gully from boot top height, but wind affected, snow to icy crust more suited to World Cup downhill record setting courses. Be on the lookout for gray old surface just peeking through the new snow. While the Chute, sections of the Center Headwall and the Lip appear attractive at first glance, remember that these areas suffered scouring as well as cross loading during the nor’Easter so the existing snow is extremely variable in thickness making more trigger points available as well as making a slide for life situation possible in places.
Huntington Ravine has a similar mix of surfaces and climbers will find it necessary to be flexible in their micro-route finding as they pick their way up a gully. Escape Hatch is currently Low hazard with not much snow to avalanche, while South and Odell Gully are not far behind with a low side of Moderate rating. Pinnacle through North gully have a greater area of bed surface and have large enough areas of new windslab that climbers should use caution when climbing these gullies as a human triggered avalanche is possible in select steep features and lee aspects.
Chris bulleted some key points yesterday which I have updated and carried over below:
Main points to remember in the field today:1. 3.3” of snow fell on Monday with high SW winds creating some instabilities on aspects with a NE facing component. 2. Since Monday afternoon winds shifted to the W and WNW peaking midday Tuesday with an additional 1.8”of snow. These Tuesday conditions developed new slabs mostly on E facing slopes. 3. New loading will came close to shutting down yesterday morning as winds dropped to 15-20mph focusing our main concern on slabs created on Monday and Tuesday. Some of these should be solidly in the Moderate rating. 4. 1/2″ of new snow in the last 24 hours has obscured many visual clues but not improved riding conditions. 5. Expect variable conditions so be ready for constant changing surfaces under foot depending on where you travel. From sweating over a long slide on icy terrain one second, to triggering an avalanche the next, plan on encountering different hazards in both Ravines.
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. Posted 8:55a.m. Thursday 2-14-2013. 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