This advisory expires at 12:00 midnight, January 12, 2013
Tuckerman Ravine has Considerable, Moderate, and Low avalanche danger today. The Lobster Claw, Right Gully, the Sluice, Lip, Center Bowl, and Chute all have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Left Gully and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The Lower Snowfields and Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely.
Huntington Ravine has Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The only exception to this rating is the Escape Hatch, which has Low avalanche danger. Natural and human triggered avalanches are unlikely.
The dreaded January thaw has arrived. There’s no good way to deliver this news, so here it is. The snowpack in the ravines was already on the thin side, and now it’s being eaten away further by warm temperatures and fog. Summit temperatures are expected to rise to around 40F (4.5C) today and into the upper 40’s tomorrow (7-10C). The worst part of it all is that it won’t drop back below freezing overnight. This will push the stability trend in the direction of increasing instability which will continue at least through Sunday. Expect avalanche danger to be rising in all areas today. Our forecasted ratings are where we believe snow stability will be for the better part of today; overnight and tomorrow stability will be worse.
As is often the case, the existing snowpack had a lot of spatial variability within many of the forecast areas, but there were some common features. In some locations there was a thin (approx.. 4”-8”) soft surface slab sitting on top of a very weak layer of heavily rimed crystals. This is going to be the canary in the coal mine, so to speak, as they will be the first areas that may avalanche naturally. However, in my mind this isn’t what I’d be most afraid of. It’s the deeper weaknesses in the snowpack that concern me more. Yesterday the upper layers of snow showed few signs that it would propagate a fracture and had good overall strength, but as the strength of the upper layers is broken down by warmth and liquid, the potential for deeper instabilities to be tested will rise. Also on the rise will be your ability to apply stress to these lower layers, whether it’s through deeper boot penetration or if you unfortunately find yourself tumbling downhill with your skis above your head. On a similar note, a small avalanche or wet sluff may generate enough force to step down into lower layers. Areas posted at Moderate and Low today generally have less snow than those at Considerable. Understand that stability is decreasing in these areas as well. I would not recommend venturing into Low rated areas unless you truly enjoy a thick, wet, bushwhack.
In addition to the increasing avalanche danger, you should be thinking about the difficulty of traveling off well beaten trails. Anywhere that the snow is deep will become a difficult place to walk without some kind of floatation such as a splitboard or snowshoes. It’s hard to believe that I’m bringing this up as early as January 12th, but you should also be wary of the potential for falling ice over the next two days. This could be a potential trigger or it just hurt you a lot if it were to hit you. And lastly, the Lion Head Winter Route is now open. This is a steep mountaineering route, so bring your crampons and ice axe and the knowledge of how to use them properly.
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.
Posted 8:20am, January 12, 2013. A new advisory will be issued tomorrow.
Jeff Lane, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856