Posted 8:20, Sunday, March 13, 2011
Tuckerman and Huntington Ravines have Moderate avalanche danger today. Natural avalanches are unlikely and human triggered avalanches are possible. The only exception to this rating is the Little Headwall in Tuckerman Ravine which has Low avalanche danger. Natural and human triggered avalanches are unlikely.
Today’s danger rating is based on the potential for continued snowfall through early afternoon and increasing NW winds. We are starting the day off with Low avalanche danger in all forecast areas. Our terrain has endured a recent rain event followed by cold temperatures that have created a very slick surface in the Ravines. The existing snowpack is quite stable and long sliding falls present a greater hazard to mountaineers than snow stability. You can expect changing conditions today as snow accumulates and increasing NW winds that will reach 35 to 50 mph (56 to 80 kph) transport new snow onto the slick surface. How much snow will we get? That is the question I have been hunting for an answer to all morning and I still can’t say for sure. Looking at all the weather data, I could easily conclude that it will be an insignificant amount. The fact that I have been observing light steady snowfall all morning that has accumulated to just under an inch has made me uneasy about what may actually fall today. The folks from the Observatory indicated that we can expect steady snow to continue until high pressure works its way in early this afternoon. It seems that our friend “upslope effect” is helping us squeeze more out of the atmosphere than models are forecasting for. This unpredictable factor is the cause for the Moderate rating. If you plan on being in avalanche terrain today, your weather observations will be paramount in assessing the avalanche danger. If snow shuts down soon, I suspect we will only have isolated areas of unstable snow developing today. If we end up measuring a few inches you can expect new snow instabilities to become increasingly problematic through the day as wind slabs build. Stay sharp out there by keeping a keen eye on snow accumulations and an understanding of how this could change snow stability in the area you opt to travel in.
As mentioned, there is a pretty icy surface in the Ravines that you don’t want to fall on. Crampons, an ice ax and solid mountaineering skills will be needed to get around safely in steep terrain. One feature to this crust is that it is still breakable in places. I spent some time in the steeps in Huntington Ravine yesterday and I found the surface conditions to be challenging. They were icy enough for me to want my crampons on in the Fan, but every now and then I would break through, sometimes to my ankle and other times to my knee. It would be pretty easy to trip and fall if you aren’t paying attention. Some sort of crust exists at all elevations on the mountain which isn’t great news for skiers and snowboards. Conditions have been quite challenging on the Sherburne Ski Trail and scary on the steeps. Hopefully today’s snow showers will improve conditions to some degree.
- 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.
Brian Johnston, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856