Avalanche Advisory for Sunday, January 26, 2014

This advisory expires at 12:00 midnight.

Tuckerman Ravine has CONSIDERABLE and LOW avalanche danger. The Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. All other forecast areas have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features.

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger. Central, Pinnacle, Odell, South, and the Escape Hatch have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. North, Damnation, and Yale have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.

AVALANCHE PROBLEMS: The primary avalanche concern today is new wind slab building through the day. Increasing wind speeds are causing a strong-over-weak scenario to unfold, which is a common theme for unstable snow. Additionally, any new slab development will be taking place on top of a snowpack with intense spatial variability, and in many areas there were already existing stability concerns before this new wind slab problem arose. The previously existing problem has been described in earlier advisories as a persistent slab problem. This still exists and makes today an even more complicated day for travel in avalanche terrain. Faceting has weakened snow layers lying beneath some harder slabs. These are reactive to triggers such as a person traveling over them, especially in locations where the hard slab is thin.

WEATHER: Currently the summit of Mt. Washington is at -26F (-32C) with winds gusting just shy of 100mph (161kph). These are very challenging conditions for travel above treeline. Even down lower on the mountain, we caution you to be conservative with your decisions today. Yesterday, the summit of Mt. Washington reported 4.4” of new light density snow. At Hermit Lake we measured 5” (12.5cm), although the snowplot had some drifting on the boards. This snow is creating the new wind slab issues, and will be limiting visibility both above and below treeline. Expect slight relief from the cold and wind later in the day, but not so much that I’d call it a comfortable day. More new snow is in the forecast for Monday. At this point, we’ll take all we can get!

SNOWPACK: Once again, spatial variability is the name of the game. Conditions varied widely as you moved around the terrain earlier this week, and the current weather will only add another layer to the mix of conditions. It will be very difficult to effectively assess an entire route from only a handful of observations. Generalizations and extrapolations can only go so far. You’ll need to constantly be alert to changes in the snowpack.

The January 11 rain crust is a good baseline to start from. Above this you’ll find faceted snow of varying thicknesses and varying levels of facet development. In many locations, you find a layer of pencil hard slab on top of the facets, again, thicknesses and strength will vary. Some other locations do not have this hard layer and others may have been scoured down to the crust. On top of all this is the new wind slab problem described above. Some areas will have a hard time holding onto the new snow with the winds raging as they are. The northern gullies of Huntington are one example. The expected scouring this morning in these areas will move them from Considerable to the current rating of Moderate for the better part of the day.

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. January 26, 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

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