Posted 8:20, Monday, March 14, 2011
Tuckerman and Huntington Ravines have Moderate avalanche danger today. Natural avalanches are unlikely and human triggered avalanches are possible. The only exceptions to this rating are the Little Headwall in Tuckerman Ravine and the Escape Hatch in Huntington Ravine which have Low avalanche danger. Natural and human triggered avalanches are unlikely in these areas.
The mountain was crawling with avalanche course students yesterday and their snow observations yielded a wide range of information. It sure seemed like we were well positioned to exceed the 1” (2.5cm) of snowfall that was forecasted for the day and moderate winds were filling the air full of snow crystals. While some students chopped through beefy rain crust others came back reporting touchy soft slabs of new, cold, windblown snow. A few of the Mount Washington Volunteer Ski Patrol joined me for some crampon and ice ax work in the bottom of Gully 3 and we found hard old surface less than 50’ (15m) away from knee-deep powder with enough energy to propagate a fracture. Such spatial variability is not uncommon here and the same type of situation holds true today. Low cloud cover has been obscuring visibility into steep terrain this morning but we did have a 90-second window where we could get eyes on a number of our forecast areas. As suspected, new windslab developed in both ravines with E to SE aspects being the greatest concern. Old surface is visible in a number of locations and smart route-finding will connect these patches to minimize risk. Though this morning’s measurements yielded less than 1” (2.5cm) of new snow anywhere on the mountain I would expect the aforementioned aspects to harbor slabs over a foot (30cm) thick in places. All of this new snow is sitting on top of slick crust and to complicate things the snow fell on increasing winds. Most of the snowfall came with wind speeds less than 40mph (64kph) before things moved up to 60+mph (97+kph) later in the evening. Such conditions create the “upside-down snowpack” that is illustrated in the textbooks of all those avalanche students who were poking around yesterday.
As mentioned earlier, there is a pretty icy surface in the Ravines that you don’t want to fall on. Crampons, an ice ax and solid mountaineering skills will be needed to get around safely in steep terrain. One feature to this crust is that it is still breakable in places. It may better support your weight in steep terrain but trying to stay on top in more gentle terrain is sort of a crap-shoot. Be prepared for challenging conditions no matter where you go. It would be pretty easy to trip and fall if you aren’t paying attention. Self arrest skills will be critical as the crust is strong enough to support your weight when you’re laying down and it’s slicker than a used car salesman. Some sort of crust exists at all elevations on the mountain which isn’t great news for skiers and snowboards. Conditions have been getting better on the Sherburne Ski Trail but that’s not saying a whole lot. Skiing today could mean hero turns in one spot while two turns later you’re skidding out dust on crust. Be smart out there and use your head for something other than a place to store your helmet!
- 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