Avalanche Advisory for Tuesday, March 18, 2014

This advisory expires at 12:00 midnight.

Tuckerman Ravine has Moderate and Low avalanche danger. The Sluice, Lip, Center Bowl, Chute, Left Gully, Hillman’s Highway, and Lower Snowfields have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Lobster Claw, Right Gully, and the Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features.

Huntington Ravine has Moderate and Low avalanche danger. Central, Pinnacle, Odell, South, and the Escape Hatch have Moderate avalanche danger. Natural avalanches are unlikely and human trigged avalanches are possible. North, Damnation, and Yale gullies have Low avalanche danger. Natural and human triggered avalanches are unlikely.

AVALANCHE PROBLEMS: Recently formed wind slab is the easiest avalanche problem to recognize today. These can be found in the uppermost layers of the snowpack in areas sheltered from the weekend’s W-NW winds. This includes the larger snowfields such as the Lip, Center Bowl, and Central Gully as well as smaller areas where cross-loading occurred despite not being directly in the lee of W or NW winds. Persistent slabs are less easily recognized, but should still be in your mind as a serious avalanche problem. These primarily exist due to a crust layer buried under much of the upper layers, though other weak layers may come into play. The persistent slab problem might be triggered either by a smaller release of the upper wind slab layer or by you simply finding the right weak point in the snowpack. This could result in a large damaging avalanche.

WEATHER: What to say about the weather today?? 15-30mph (24-48kph) winds and summit temperatures reaching the teens F (-9C)…this sounds like a fantastic WINTER day. Don’t let the sunshine fool you, it ain’t spring just yet. I’d recommend Cranmore Mountain today for those who don’t care to travel with avalanche gear. Those south-facing slopes in the valley will probably warm up quite nicely, especially compared to up here.

SNOWPACK: As mentioned above, the first thing you need to be looking at today is the uppermost layers in the snowpack. After last week’s storm, we received several inches of additional new snow. Early on Sunday morning, winds kicked up with gusts almost to 100mph. The resulting wind loading filled in many of the crown lines left by previous avalanche activity, as well as building slab in areas that had already been reloaded. The second thing to assess for is the underlying weaknesses, aka persistent slabs. Spatial variability will make it difficult to make assessments in one location and extrapolate the findings to another.

I expect solar energy to be a favorable player in today’s stability on aspects that are in the sun. While temperatures shouldn’t be rising high enough to moisten the surface snow, the solar gain should help to stabilize the wind slab that we are concerned about. The more a slope faces into the sun, the stronger this effect will be. Also, the shallower the wind slab layer, the stronger this effect will be. For example, do not expect similar stability in the Lip if you just climbed and assessed the snow in Right Gully. RG gets more direct sun and has thinner, smaller slab problems; the Lip is more oblique and will have deeper wind slab layers. Also, do not expect the solar gain to do much for stabilizing the persistent slabs. These will need more than yesterday and today to fully stabilize them.

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 Visitor Center, or the caretakers at Hermit Lake Shelters and Harvard Cabin.
  • Posted 8:30a.m. 03-18-2014. 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

2014-03-18 print friendly