Avalanche Advisory for Saturday, April 18, 2015

This advisory expires at 12:00 midnight.

This morning, all forecast areas of Tuckerman Ravine have LOW avalanche danger. Natural and human triggered avalanches are unlikely.  This afternoon, Sluice, Lip, Center Bowl and Chute will have MODERATE avalanche danger. Natural avalanches will be unlikely but human triggered avalanches will be possible. Evaluate snow, weather and terrain carefully.

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: Wind Slabs will build this afternoon as wind carries and deposits 2-4” (5-10cm) of new snow in our start zones. The exact size and touchiness of these slabs will depend on the density of the snow and timing of the wind increase. Generally speaking, the new snow will be “upside down” with denser, wind packed snow over lighter density and therefore weaker snow. The wind slab problem will increase into the evening as snow showers drop another trace to 2”. Until that time when these wind slabs build, minor and manageable Wet Loose avalanche activity is possible as morning sun heats our south and southeast facing slopes.  Steep slopes that have seen a lot of ski traffic generally have less of this type of problem. Areas without recent ski traffic have the greatest potential for larger sluffs.

WEATHER: Bluebird skies, calm winds and temperatures hovering near the freezing mark this morning will give way to building clouds, mixed precipitation and snow this afternoon. Currently, light westerly summit winds in the 20-35 mph range are blowing but will increase to the 50-70 mph range this afternoon. Hour by hour forecast models indicate that the mixed precipitation will begin in the early afternoon hours and quickly change to snow as temperatures drop. This frontal activity will raise clouds capable of producing intense shower activity, which will play out as thunder storms at lower elevations, so the exact amount of snow is hard to pin down. Two to four inches (5-10cm) of snowfall during daylight hours is predicted which, when coupled with building winds, is driving our increased avalanche danger rating. Navigation will become increasingly challenging as visibility diminishes with fog and blowing snow.

OTHER HAZARDS: The snowpack is slowly moving downhill as a unified mass and is pulling away from cliffs, creating crevasses. New snow may obscure these slots with easily breakable snow bridges. Be aware of what is above you today, especially as the sun continues to bake south faces this morning.  Realize that hanging out at Lunch Rocks puts you directly in the runout of large pieces of falling ice. Also, undermined snow is creating challenges for exiting the Bowl. While the Little Headwall is still skiable, there is open water both above and below. The best exit from the Bowl may involve walking to Connection Cache and possibly farther. Numerous areas of large ice have horizontal cracks forming and the Sluice ice, above Lunch Rocks, is already missing some chunks.

SNOWPACK: Nighttime temperatures allowed refreezing last night. Expect a mix of harder surfaces where crampons would be helpful if not necessary, as well as a breakable crust that gives way to deeper slushier corn snow. As temperatures drop this afternoon, shadier aspects which did not benefit from the softening power of the morning sun will become even harder. The potential for long sliding falls and very difficult self-arresting conditions should be on your mind today.

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 Mount Washington Volunteer Ski Patrol, or the AMC at the Pinkham Notch Visitor Center and Hermit Lake.
  • Posted 8:00 a.m., Saturday, April 18, 2015. A new advisory will be issued tomorrow.

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