Posted 8:45a.m., Tuesday, December 21, 2010
Tuckerman and Huntington Ravines have Considerable avalanche danger today. Natural avalanches are possible and human triggered avalanches are likely. We have not begun forecasting for the Escape Hatch, Lobster Claw, 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.
Well it finally feels like winter and guess what? It is! We all wanted to see last night’s lunar eclipse but if it wasn’t possible I’d personally settle for a little low density powder to ring in the winter. Snow began falling yesterday around sunset and by midnight the summit had picked up 2.2” (5.5cm) of 6% light density fluff. Another 2-4” (5-10cm) is expected over the course of the day today. Winds remained out of the N at around 35mph (56kph) for much of the evening but this was plenty fast enough to send the snow flying. As the day moves along we expect to see an increase in speed as the Observatory is forecasting winds up to 65mph (105kph) with higher gusts.
One of the more critical pieces of information that seems a little more difficult to pin down today is the wind direction as we feel the lingering effects of the storm that recently passed us a little too far to the E. The Observatory’s summit forecast calls for NNE winds today while the National Weather Service is expecting them to come from the NW. It may not seem like a big deal but the combination of topography above the ravines (Bigelow Lawn and Alpine Garden), forecast area aspect, and existing bed surfaces make this an important piece of information. NW winds tend to deliver much more snow to the ravines than those from the N or NE. If we were better able to pin down the direction we might be able to drop some forecast areas down to the Moderate rating. I would expect areas with a southerly aspect to reach the Considerable rating well before other areas make the jump today. These include the Right Gully, Sluice and Lip in Tuckerman and Yale, Damnation and North in Huntington. Soft and touchy windslab will likely develop over unconsolidated low-density snow in these lee areas where protection from the wind is highest. This layering will cover what had been at the surface—a mixture of compacted snow/neve with scattered areas of faceting. Areas that have an easterly or northerly aspect will still pick up snow but this will be mostly through cross-loading. Instability issues will be slower to develop in these spots but the layering described does not lend itself well to stabilization. If you’re out in avalanche terrain today it will be essential to exercise careful snowpack evaluation, cautious route-finding and conservative decision-making.
The lower sections of the Tuckerman Ravine Trail have been an icy nightmare and have made all of the Snow Rangers firm believers in lightweight traction footwear. I rarely wear crampons below Hermit Lake but some of the past days have made me wish that I had ten big spikes on each foot and maybe even a couple of ice tools to run laps on some of the crazy ice flows that have developed off the sides. Long, nasty sliding falls are possible in a few areas and some snow on top will make these hard to detect. Be careful out there or you’ll end up broken and tossed in the woods somewhere along the way!
- 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