|Posted: 9:10a.m., Saturday, December 18, 2010|
Tuckerman and Huntington Ravines have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.
If you’ve been paying attention to the weather up here, you might have noticed that we haven’t gotten a big storm since the rain event about a week ago. You might also be wondering what change has prompted us to move from General Advisories to the North American 5-scale danger rating system. While the rain from that last storm was a setback, on its heels it left behind 5.6” (14cm) of snow. Since then, light accumulations have continued, bringing the post-rain snowfall totals up to 9.8” (25cm). During this time temperatures have been cold and winds have been rather light.
This pattern has helped further the growth snowfields in the ravines, but more importantly it left behind a fair bit of light density snow in the upper elevations. Winds yesterday topped out at 50mph (80kph) from the NW, the strongest they’ve been since Monday. You can expect that snow that had been sitting above treeline was transported into the ravines late yesterday. Wind speeds forecasted for this weekend are light enough to keep new loading to a minimum. The shift to today’s Moderate rating reflects our concerns about recently developed slabs as well as the continued growth of bed surfaces and avalanche paths. Anticipate some new slab instabilities to be on the upper end of the Moderate rating particularly in some of the larger snowfields in Tuckerman. Sporadic visibility in between extended periods of fog and blowing snow over the past several days has limited our ability for a complete assessment of the terrain. Clearing conditions for the weekend should help us gather additional information for a more complete picture.
As mentioned, the growth of the snowfields in avalanche terrain has been slow but steady. The largest continuous snowfields can be found in places such as Left Gully and the Chute in Tuckerman, and Central and Odell gullies in Huntington. Most other forecast areas also have snowfields large enough to avalanche. However, there are some areas with little or no snow. Getting around in places like the Lower Snowfields or the Escape Hatch would be difficult, to say the least. If you’re heading into avalanche terrain today, you should come ready to assess snow stability carefully. Bring along your beacons, shovels, and probes, but remember rescue gear doesn’t guarantee your safety. Not getting caught in an avalanche in the first place should be your real priority.
Jeff Lane, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856