Avalanche Advisory for Sunday, April 27, 2014

This advisory expires at 12:00 midnight.

Tuckerman Ravine has Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

Huntington Ravine is under a General Advisory. You will need to do your own snow stability assessments when traveling in avalanche terrain in Huntington. A danger of falling ice exists, and will persist until it all comes down.

AVALANCHE PROBLEM: The possibility of wind slabs developing during the day caught my attention and had initially driven up the danger rating for select areas. Then the fog in the ravine lifted momentarily and I was able to see that yesterday’s new snow did not blanket the old surfaces the way I was thinking they would have. This visual clue was a key factor in keeping danger ratings at Low today. However, you should be on the lookout for small pockets of wind slab in all areas regardless of the Low rating. The most likely locations for unstable slab to develop will have a S or SE aspect. This is due to winds shifting to the N and increasing in speeds late today.

WEATHER: Yesterday and overnight we received 3” (7.8cm) of new snow at Hermit Lake. This began to fall with winds 30-40mph from the S, then they lessened to 15-20mph and shifted to the NW as snow continued to fall. Today we expect an increase back up to 35-50mph and a further shift to the N. Additionally, we may receive a trace to 2” of additional accumulations today. Ravine temperatures today will only be hovering near freezing, so don’t be looking for soft spring snow. Visibility may be poor at times as fog comes and goes.

SNOWPACK: After hiking up to find 3” of new snow coating everything in sight, it was a bit of a surprise to see up into the Lip and Sluice while writing and easily see old surfaces showing through in more or less all areas. My impression of what happened is that the light winds were not able to transport the high density snow, so it just stayed in place wherever it fell instead of building into deeper drifts. Beneath the dusting is an icy surface that has been thoroughly stabilized by previous melt/freeze cycles. As winds ramp up, new wind slab development may take place today, especially if we get another 2” of snow. There are factors working in favor of keeping new slab from being unstable, such as the rough textured bed surfaces, high density snow, and relatively warm temperatures. Be watchful for thin weak layers beneath newly formed slabs.

OTHER HAZARDS: Long sliding falls are a potential hazard today snow surfaces stay frozen. An ice axe and crampons will help keep you safe, but knowing how to effectively use them is every bit as important. Practice before you put yourself into “no-fall” terrain. CREVASSES have been late in emerging this season. Currently they are mostly buried and not a problem. The most notable exception to this is in the Lip, other smaller holes exist in Sluice and elsewhere. There is also some undermined snow in Right Gully and Lobster Claw.

The Lion Head Winter Route is still open. This is a steep icy trail. An ice axe, crampons, and the ability to use these tools effectively are highly recommended. Lightweight trail crampons lose their effectiveness in steep terrain.

The John Sherburne Ski Trail is open to about 1 mile from Pinkham and closed below this point. Expect lots of bare patches, icy sections, and enormous bumps 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 Mount Washington Volunteer Ski Patrol, or the AMC caretakers at Hermit Lake or Pinkham Notch Visitor Center.
  • Posted 8:35a.m. 4-27-2014. 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

 2014-04-27 Print Friendly