All forecast areas of Tuckerman and Huntington Ravines will have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. The only exceptions to the Considerable rating are the Lower Snowfields and the Little Headwall, which have Low avalanche danger. In these areas, natural avalanches are unlikely and human triggered avalanches are possible.
There are two important factors to the avalanche advisory today. The first is related to snow that fell and was blown around yesterday, the second is the additional wind loading that may take place during the day. These factors each affect different aspects, so your choice of routes and ability to safely navigate through various snow conditions will be critical to avoiding avalanches. Avalanche danger will be increasing today.
Yesterday, Joe and I thought we could make a quick trip up through Tuckerman to take a look at what appeared to be an crown line high up on the Lion Head ridge. As we got into the Bowl, snow began falling at a good rate and SW winds began to crank. When we topped out of the Lobster Claw, it was pretty clear that we weren’t going to be taking any extra time to look around. The strong SW winds were nearly knocking us to our knees, so you can imagine what it was like for all the snow above treeline that was exposed to the winds. Snow was being transported across the flatter terrain and depositing in steep lee aspects such as Hillman’s, Left Gully, the Chute, Odell Gully, and South Gully. Stability issues leftover from yesterday will most likely be found in aspects ranging from N-facing to E-facing, as well as sheltered pockets in other areas. Overall yesterday, the summit recorded 3.3″ (8cm) of new snow before midnight and a little more since then. Our snowplot at Hermit Lake had 3″ (8cm) as well.
The weather forecast for today is calling for 1-3″ (2.5cm to 7.5cm) of additional upslope snow, thanks to an upper level trough, favorable wind directions, and low level moisture in the atmosphere. Winds today will be blowing strong from the NW, at 60-80mph (95-130kph) with higher gusts. These shifting winds will be able to find snow where the SW winds couldn’t, and it will be blown into the ravines. How much new snow we will actually receive is little more uncertain. We’re rating the ravines today on the hope that we’ll get 2 or 3″ of new snow, which will mix with the older snow being relocated to new homes on steep lee aspects facing to the S, SE, and E. These slopes are starting the day in the Moderate range, but will rise into Considerable will additional slab development. As time passes, the possibility of naturally triggered avalanches will increase from “unlikely” to “possible,” which is to say we’ll be moving from Moderate to Considerable avalanche hazard.
The Lower Snowfields and Little Headwall are currently rated at Low danger. If we were in December instead of February, we’d be saying they are “not posted due to an overall lack of snow in these areas.” In reality, there is little quality recreational opportunities in these areas at this time. The Little Headwall resembles an ice climb. It is not a good option for descending out of the Bowl. The Lower Snowfields are still a tangled mess of shrubbery, but they are exposed to avalanches coming from slide paths above. Hillman’s Highway, in case you were wondering, is still a mess in the lower half. The January rain created a slush path in the lower third which is now a refrozen mix of old slush, sand, gravel, and tree branches.
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 8:09 a.m. February 12, 2013. 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