Posted 8:25a.m., Thursday December 23, 2010
Tuckerman and Huntington Ravines have Considerable avalanche danger today. Natural avalanches are possible and human triggered avalanches are likely. Note that we have begun forecasting for the Lobster Claw today and is included in the Tuckerman rating. We have not begun forecasting for the Escape Hatch, Lower Snowfields, or Little Headwall due to a general lack of snow in these areas. Forecasting will begin for these areas when conditions warrant although avalanche activity may occur before this point.
It’s not as obvious as a 2 foot dump with big winds, but today is certainly a period with avalanche potential on Mount Washington. Higher elevations picked up a bit over 4” (10cm) of snow as of midnight and it continues to fall. This adds up to over 8” (20cm) for the past three days associated with a predominately N to NNW wind. Maximum wind speeds have nudged just a bit higher each day with this afternoon seeing a substantial increase in velocities. The Mount Washington Observatory and the NWS expect gust potential between 70 and 80 mph (112-128kph) later today with additional snowfall potential between 2-4” (5-10cm).
These weather conditions will continue the mountain’s increasing avalanche trend pushing towards the upper end of the Considerable rating later this afternoon. The snow accumulations and expected winds would typically have us thinking about a High rating during a normal late December-January date. However, the amount of anchors in the form of rocks, turf, and vegetation still plague a number of areas making snowfields smaller and less contiguous than the average mid winter day. These issues will, in a few areas, assist some slabs from failure (a.k.a. avalanching), but this anchoring should not occur everywhere especially aspects with S, SE, and even E facing components which will see substantial loading during today’s daylight hours. Tuckerman’s Right Gully, Lip, and Center Bowl under the headwall ice are some examples of areas to consider avoiding. Remember to evaluate certain gullies with a multiple aspect start zone carefully. Left gully is an example of a classic broad bowl-like top having a very steep south facing wall that will receive direct loading today from N winds even though much of the gully faces E and NE. Everything points to a heads up day and to put it most simply, we could possibly see some natural avalanche activity that is larger than anything seen thus far in the 2010-2011 season.
Clear weather is expected to move in tomorrow and for Christmas Saturday. We are excited to see what this latest round of weather and potential avalanche activity has done to the terrain. We will relay anything we find right here at www.mountwashingtonavalanchecenter.org. Check back and stay tuned.
- 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.
Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856