Avalanche Advisory for Tuesday, February 18, 2014

This advisory expires at 12:00 midnight.

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

All forecast areas of Huntington Ravine will have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches will be possible.

AVALANCHE PROBLEMS: Depending on how late you are on the mountain today, you will either be facing pre-existing wind slab stability problems or new storm slab problems as your primary concern. Of course, if you’re out late enough in the day for storm slabs to be a problem, you will still have the older wind slabs, which will make for a more complicated and dangerous situation. Avalanche danger will be increasing late today with incoming snowfall. Don’t discount the idea that we may have dry loose avalanches that can be large enough to either entrain you as it passes, or to act as a trigger for a much larger slab avalanche.

WEATHER: A Winter Weather Advisory is in effect until 1am tonight. 3-5″ (8-13cm) of new snow is expected for the Mt. Washington area, slightly higher totals are expected farther to the south. This should get started in the afternoon and go through the evening, during this time we may have periods of heavy snow squalls. An interesting weather feature over the next 36 hours will be the wind directions. This will have a very strong influence on how the incoming weather affects snow stability. Generally, today’s winds will be from the SE about 25-40mph during the time snow is falling. At some point after dark, there will be a rather quick flip in the wind direction to the NW and then the W. This should happen over only a few hours, so new direct wind loading on S-facing slopes will be limited. Tomorrow winds will more slowly shift from the W to the SW and some additional snow will fall in the afternoon.

SNOWPACK: Today’s ratings reflect the anticipated snowfall coming late today. Until this happens, the snowpack is at a similar danger level as yesterday. Field observations showed significant scouring in many of gullies in Huntington. This was probably made more prominent by yesterday’s winds after we had been there, which peaked at 107mph (172kph). There were isolated areas of concern, such as the approaches to the ice in Pinnacle, Central, and Yale, as well as smaller pockets scattered throughout the ravine. Today, the northern gullies will struggle to make it into the Moderate rating. In order for this to happen, we will need to see the upper end of the forecasted snow totals. If we don’t get there, expect small cross loaded pockets of slab as well as the potential for dry loose avalanches.

In Tuckerman we also saw scouring effects, notably in Hillman’s, Left Gully, and upper parts of the Chute. Near the bottom of the Chute was a very large and strong slab comprised of sluff debris, about 80-100cm deep in the middle, sitting on top of a softer weaker layer below. Where it was thickest, this slab was strong enough that triggering it would have been difficult, but the potential consequences of doing so should raise your hackles a little. We also made it into Right Gully, which grew tremendously in the last couple weeks. The key thing to remember here is that the snow you see is only just barely hiding numerous rocks. These rocks and bushes can act as hidden weak points in an otherwise strong snowpack. The Lip and Center Bowl are the currently the areas of greatest concern. They’ve grown also quite a bit recently. Bed surfaces are becoming more connected to each other, so it’s more likely we will see avalanches capable of propagating crown lines farther than previously this season.

Incoming storm slabs will begin forming in areas such as Hillman’s and Left Gully in Tuckerman, and Escape Hatch, South, and Odell in Huntington. As time passes and more snow falls, there will be more cross loading taking place in E-facing slopes such as Pinnacle, Central, Center Bowl, and the Lip.

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 7:45 a.m. 2-18-2014. 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

2014-02-18 Print friendly