Posted 8:34 a.m., Wednesday, December 22, 2010
Tuckerman and Huntington Ravines currently have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. 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.
In our forecaster’s meeting this morning we had a good discussion of the current issues effecting avalanches that had us going back and forth between a mostly “moderate” situation or trending towards “considerable”. We decided that moderate best reflects today’s stability with a few caveats. Yesterday morning we reached a peak wind speed of 62mph (100kph) on the summit from a northerly direction, which was the highest velocity in quite some time. We anticipate this moved Monday’s 2” of snow and the past several days of modest accumulations before that into a number of southerly aspects. However, some weather forecasts were calling for a NW wind which historically gives us greater instabilities than what actually occurred from the N, hence the “Considerable” forecast. This NW direction did not come to fruition so a number of areas were struggling to meet Tuesday’s rating and likely spent the day sitting in the “Moderate” range.
This morning’s weather report is very similar to yesterday. We picked up another 2” up high as of midnight with a northerly wind currently blowing at about 30mph (48kph). Winds are expected to pick up later today approaching 50+mph (80kph). This should be associated with an additional 1-2” of snow which will put us on an increasing avalanche trend. Generally, we would be most concerned about aspects in the direct lee of the current and expected winds. Today this would mean slopes pointing towards the south. Right now our southerly facing slopes and gullies are still a bit boney nevertheless they do have enough snow to act as a base layer for avalanche activity. But these snow patches are not nearly as large or continuous as they will become later this winter. South facing start zones in Huntington’s Yale, Damnation, and North gullies as well as Tuckerman’s Right Gully and the Lobster Claw are still small and broken up by rocks and bushes in many places. So although it is important to recognize these locations as the primary locales for new loading we have more concern for some of our more well developed aspects. Tuckerman’s Sluice, Lip, Chute, Left Gully and Huntington’s Central have larger snowfields and are more cause for concern than the aforementioned southern aspects. Left Gully and the Chute sit almost perpendicular to today’s wind and usually see some cross-loading as well as scouring with moderate winds. Although close in compass direction to these, the more protected Center Bowl and Lip should see greater snow instabilities and they stand out for us as the main areas to be concerned about. Light snow densities coupled with modest winds should allow the development of scattered soft slab that may be reactive and touchy. As the day progresses be aware that avalanche danger is on an increasing trend allowing a number of open slopes with a south to easterly aspect to move towards the upper end of the Moderate range. As we move into tonight additional snow and winds will have the ratings hedging toward the Considerable definition.
- 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