Posted 8:25am, Thursday January 27th, 2011
Tuckerman Ravine has Moderate avalanche danger today. Natural avalanches are unlikely and human-triggered avalanches are possible. The only exceptions to this rating are the Little Headwall and Lower Snowfields which both have Low avalanche danger. Natural and human-triggered avalanches are unlikely in these areas.
Huntington Ravine has Moderate avalanche danger today. Natural avalanches are unlikely and human-triggered avalanches are possible. The only exceptions to this rating are North Gully, Damnation Gully, and the Escape Hatch which have Low avalanche danger. Natural and human-triggered avalanches are unlikely in these areas.
We are in the middle of a series of weak weather disturbances that will present brief periods of clearing, dropping fog, and obscured summits over the next 2 or 3 days. In addition to this some very light snow accumulations can be expected, which for each day should be minuscule, but has a tendency to make a difference over time. Historically we’ve called this getting “nickel and dimed”. My mom always told me every penny counts and I’m telling you the same in terms of snow accumulations. The mountain has a way of saving up these small amounts waiting for a good wind event to load up some slopes, so although I don’t expect significant widespread instability we will likely be bumping along in the Moderate rating based on thin new slabs of concern. This whole concept of light snow amounts jumps out at you if you look over January’s snow totals on the summit. We are running at only about 66% of average for the month but it has snowed 21 out of 26 days. Of these only 3 days were over 2” (5cm)! Talk about a pittance from day to day but the pennies add up. The other major point of these low snow amounts is the majority of them are upslope events caused in combination of energy and moisture in the valley with the orographic lifting of the mountains. This usually happens under colder conditions which generates low density snow in the 4-7% water content range. This is then easily transported by even light winds into touch soft slabs.
Bringing all this to today’s issues the summit picked up 1.4” (3.5cm) Tuesday and 0.4” (1cm) early this morning. Initially this precipitation came in on W winds from 50-65mph (80-105kph) 36 hours ago to a diminishing wind from all points on the compass rose over the past 24 hours. This brought in some soft slabs mostly into E facing aspects and some minor cross loading of N and S facing slopes. The top of Right Gully is an example of these S facing aspects. One visual clue we’ve been watching is the fracture line from the Center Tuckerman Bowl avalanche on Saturday. The crown continues to disappear, demonstrating that at least a foot an a half of new snow has been deposited near this area of the Ravine. The new loading over the past 48 is layering over the very cold slabs we had in place from last week’s storm. The cold weekend brought temperatures down to -35F (-37.5C) on the summit early Monday morning. The slow warm up has started helping slabs, but our snow stakes near both Ravines are showing very limited settlement hinting consolidation is still at a crawl.
The key points today are:
- A skilled student of avalanche terrain travel with good stability assessment skills can find reasonable routes in both ravines if they pay attention to changing snow conditions and a high degree of variability.
- You should expect new instabilities from the past 48 hours to be light in density and touchy to human triggers.
- A chance of new snow is forecasted for this afternoon and tomorrow on a building NW wind climbing to 55+ mph (88kph) by late today. Expect this to bring in some additional light snow deposition high in the start zones of both Ravines.
- 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