Avalanche Advisory for Tuesday, 3-26-2013

This advisory expires at 12:00 midnight, March 26, 2013.

Tuckerman Ravine has Moderate and Low avalanche danger today. The Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. All other forecast areas have Low avalanche danger. Natural and human triggered avalanches are unlikely, however, watch for unstable snow in isolated terrain features.

Huntington Ravine has Low avalanche danger today. Natural and human triggered avalanches are unlikely, however, watch for unstable snow in isolated terrain features.

Compared with yesterday, avalanche danger ratings have dropped one rating across the board. Areas that were Considerable yesterday are now Moderate; those that were Moderate are now Low. I say this not to give you the green light to forget everything you learned in your avalanche class and blindly climb or ski every line you want, but to highlight the idea that just yesterday avalanche danger was rated higher. There are still avalanche problems to contend with, even in areas rated at Low danger.

The first problem you’ll want to know about is the leftover slab from weekend snow and wind loading. This triggered some large natural avalanches that left behind sizeable hangfire. The slabs that developed but didn’t avalanche during this event have now had a couple days time in which to work towards stabilization. In many locations, you’ll find thick strong slab that would be difficult to trigger. However, there may be more easily triggerable points lurking under the snow. These include locations where the dense slab is thinner or softer, allowing the stress bulb from your skis or boots to penetrate deeper, perhaps to a weak layer. Another example is where there is a greater difference in density between the firm upper layer and the soft lower layer. This implies weaker snow below, which could act as the weak layer. Yet another example is where windloading took place on a prior bed surface from avalanches over the weekend, such as in the Sluice, Lip, and Center Bowl. These problems are mostly found in the Moderate rated areas, but smaller terrain features, such as the steep skier’s right side of Right Gully, are locations where you can also find them. You’ll stand a good chance of finding reasonably stable snow if you go looking for thick strong slabs with little change in density as you look deeper.

The second problem is one that may develop today. Last night we received a dusting of new snow (2-2.5cm) which may be blown into the upper start zones by 25-45mph (40-70kph) NW winds. This will be a lesser concern than the existing slabs, but if you see it developing you may want to take notice of it. Expect S, SE, and E aspects to receive the most additional wind loading.

Our terrain has turned a corner and now feels “big” to me, whereas throughout this season it seemed much less imposing. We’re at the point of the season where your safe travel practices and ability to assess the snowpack in a spatially variable environment can lead to a positive experience in the ravines, and may allow you to take some runs from the tops of the routes.

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 8:30 a.m. Tuesday, March 26, 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

2013-03-26 Printable