Posted 8:23a.m., Sunday, February 06, 2011
Tuckerman and Huntington Ravines have HIGH avalanche danger today. Natural avalanches are likely and human-triggered are very likely. Travel in avalanche terrain is not recommended. The only exception to this rating is the Little Headwall which has Moderate avalanche danger.
What an exciting 24 hours it’s been! Yesterday morning we started the day with a large natural avalanche in the Center Bowl. The failure of the slab was not that surprising but it serves as a good reminder of how a seemingly small amount of wind-loading can tip the scale even under bluebird skies. Clouds settled in by mid afternoon and by the time we left the mountain blizzard-like conditions had engulfed the area. Snow came in with a vengeance, making all the snow lovers giddy with excitement. Unfortunately snow gave way to mixed precipitation before midnight and a crust began to form at most elevations. This crust was soon buried as the amazing and elusive thundersnow poured out of the storming skies. By daybreak winds had made the swing to the NW and ramped up to 80+mph (129+kph). The summit picked up just under 10” (25cm) while we got a few inches less at Hermit Lake. Right now at Hermit Lake it’s 15F (-9C) and the wind is sending snow and ice pellets whipping through the air. Winds are forecasted to back off a little later in the day but for now there is significant wind-loading occurring in both ravines. At Hermit Lake the crust is about .1” (6mm) thick and buried 2.5” (6cm) down from the surface where wind hasn’t either torn it apart or buried it deeper. It is unclear how the crust developed in the start zones but we do know that the summit received their share of thunder-driven ice pellets last night. Although the average snow densities are skewed by these pellets and the other forms of mixed precipitation that fell, the snow above and below the junk is actually of an average density. Another trace to 2” (5cm) may fall over the course of the day today and add to what’s available for transport. We expect that when the clouds lift we’ll see evidence of an impressive avalanche cycle. Most paths were finally reaching maturity before this storm and a few have made some impressive runs. This storm will likely extend their debris fields even farther so I’d advise against trying to “just go close enough to have a look.” With today’s visibility that means getting yourself into a run-out and risking a burial.
- 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