Avalanche Advisory for Monday, April 13, 2015

This advisory expires tonight at 12:00 midnight.

All forecast areas of Tuckerman Ravine have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features. Unstable snow may exist on isolated terrain features.

A General Advisory is currently issued for Huntington Ravine. We have stopped issuing daily avalanche forecasts for Huntington for the remainder of the season. You will need to do your own stability assessments when traveling through avalanche terrain. A danger of falling ice will begin to increase, along with other spring hazards, with the seasonal warm-up.  These hazards will persist until melt-out as we transition into early summer.

AVALANCHE PROBLEM: Loose wet avalanches are the primary threat today, with a remote possibility of wet slabs hanging in the shadows. The problems are being driven by yesterday’s warming, the mid-elevation warm band overnight, and today having some of the warmest temperatures we’ve had yet this season. Overall, avalanche activity is unlikely aside from loose wet sluffing in areas that saw few skiers or riders yesterday. The wet slab problem could create a large avalanche, but we feel the likelihood of this taking place is low enough to warrant a Low rating. However, the snowpack is not so stable at this point that I’d leave the beacon, shovel, and probe in the car.

We are also beginning to see weather conducive to the annual spring hazards, such as FALLING ICE, CREVASSE FORMATION, AND UNDERMINED SNOW. These have been kept in check by the cold temps so far this spring, but nevertheless, be alert for them today and in the coming weeks. The streambed from the floor of the ravine to the Little Headwall will have weak snow bridging over some deep water holes.

WEATHER: The previous few days have provided conditions that led toward the stabilization of the snowpack. Friday was a warm, wet and rainy day, followed by refreezing on Saturday. On Sunday, temperatures rose sufficiently to thaw the surface layers of the snow at all aspects and elevations. Last night, temperatures in the ravines stayed warm, without the ambient air temperature going below freezing. Things will only get warmer today – the summits will reach into the 40F range. Winds, starting the day fairly light, will increase in the afternoon along with some cloud cover coming before a precipitation event late today and tonight.

SNOWPACK: The melt-freeze cycle from the weekend did indeed help stabilize the snowpack, but we have unanswered questions as to how far down into the snowpack this effect can be found. Lingering in the back of my mind is the question of whether today’s heating will increase the potential for warm wet slabs fracturing over cold dry weak layers that may be buried deep enough to have not been stabilized by the melt-freeze action. If last night had gone below freezing, this would probably be off my radar. But the lack of a refreeze does have me wondering. Digging into the snowpack to look for how deeply the melt-freeze layer extends may not be a bad idea. Again, the likelihood is remote, but the fact is that Mount Washington is not a man-made environment. There is always some risk of the unexpected.

Note: The streambed leaving the bowl is not a recommended exit route. It has melted out to the point where you cannot ski down the stream until you are below the first aid cache. Both the skiers’ right and left side are also melted beyond the point where we recommend this way out (i.e. you’d be walking over rocks and trees). It is far easier to take off your skis/board, walk down the hiking trail 100 yards to the first aid cache, then begin skiing again from there. Be wary of undermined snow between the cache and the Little Headwall. The john Sherburne Ski Trail is still open to the bottom, but we are beginning to see a handful of bare patches and rocks emerging. Also, there are some large moguls throughout the trail.

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 8:15 a.m. Monday, April 13, 2015. A new advisory will be issued tomorrow.

Jeff Lane, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2713

2015-04-13