Avalanche Advisory for Sunday, 3-31-2013

This advisory expires at 12:00 midnight tonight.

Tuckerman and Huntington Ravines have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

Before we begin, let me remind everyone that Low avalanche danger does not mean no avalanche danger. It can often come pretty close to that after strong melt-freeze cycle or other similar events, but we’ve had no such event that would put the snow at the lower end of the Low rating. Instead, we’ve come to today’s rating through a combination of settlement over time, solar gain and mild temperatures, and numerous volunteer stability testers (e.g. skiers, ice climbers, and even a large German shepherd rag-dolling in the Lip).

You’ll find a variety of snow conditions as you move around in the ravines. Yesterday was bright and sunny up here, though it stayed deceptively cool throughout much of the day. Aspects facing strongly to S did receive enough heating to moisten the surface, and in some cases made for heavy wet snow. I found this to be the case beneath North and Damnation gullies in Huntington, but as a traversed underneath Yale, a slightly different aspect, the solar gain was much less noticeable. By the time I got to NE and N aspects, it was clear that the snow had remained cold and dry. Tuckerman was much the same, with Left Gully staying dry and Right Gully being wet. Between these two areas the snow will range from dry windblown to crusty chopped up that will make you hope the sun can work its magic on the slopes.

Avalanche concerns today are a little different than a typical Low, where we advise people to “watch for unstable snow in isolated terrain features” or sometimes we refer to isolated pockets. The thing that gets my attention today is the potential for someone to hit an isolated trigger point in an area that did not get tested a lot by skiers or climbers yesterday. For certain, there were a lot of skiers getting into the Lip, Chute, and left side of the headwall. Areas that weren’t thoroughly tracked up are the ones to watch for, such as the icefall area and the Sluice in Tuckerman and above the ice in Odell and Central in Huntington. Overall stability in these locations is good, but there may be weak points near buried rocks or ice, or at the edges of slabs. If something were to release in these locations it would be too large to call it an “isolated pocket”. With this in mind, my advice is to stay vigilant to changing snow conditions, keep up the habit of using safe travel practices, and pay attention to who is above or below you.

We’ll see clouds on the increase later today and precipitation beginning as early as this afternoon. It would be a good day to get an early start. The John Sherburne Ski Trail saw above freezing temperatures yesterday and plenty of traffic. This means conditions will be similar to a resort whose groomer has been broken down for a week. Hopefully warmth will soften it again this afternoon.

Please Remember:

  • 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 at 8:30a.m., March 30, 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

2013-03-31 Printable