Avalanche Advisory for April 1, 2017

This advisory expires at Midnight tonight.

Huntington and Tuckerman Ravines have CONSIDERABLE avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Careful snowpack and weather evaluation, cautious route finding and conservative decision making are essential. The only exception to this rating is the Little Headwall, which has MODERATE avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.

AVALANCHE PROBLEM: Storm slab avalanches may propagate a crack and avalanche today with a human trigger due to increasing cohesion within the new snow from warming temperatures. Though wind is generally light, especially by Mount Washington standards, recent gusts from the east in the 40 mph range on the summit will contribute to this slab formation. In addition to the storm and wind slab problems, significant sluffing will occur both naturally and as a skiers or riders push snow around. Due to the high density of the new snow, these sluffs could entrain a lot of snow. Today is a really good day to consider the nature of your runout. Think about terrain traps, trees, boulders or cliffs in your fall line and stick to lower angled slopes. The Little Headwall area contain a couple of open holes to the stream below.

WEATHER: 10” (26cm) of 10.8% density snow was recorded by 6:30am this morning at Hermit Lake and is falling steadily at a rate of a little less than an inch per hour. With the low pressure stalling offshore and enhanced snowfall at higher elevations, we seem to be on track to get 3-5” more snow by this afternoon. East winds are blowing at 37 mph with a recent gust of 45mph. Summit temperature is 14F currently with 28F at Pinkham Notch. The summit is expected to reach the lower 20’s F this afternoon, with temps around freezing at Pinkham Notch. Visibility at higher elevations will be reduced due to summit fog and snowfall so safe travel techniques and navigation will be tricky today.

SNOWPACK: At this time, 10 inches of new snow has fallen at Hermit Lake, and it’s still coming down. This relatively warm snow, which has experienced mild wind effect from the sustained 30-40 mph E wind, will exhibit an upside down nature in many areas. As temperature rises today, cohesion in the storm slab will increase potential for a fracture to propagate over a large area. Areas less wind affected will exhibit less cohesion in this new snow, but will sluff easily and in large amounts on steep slopes. Underneath this new layer which blankets all of our terrain, you’ll find a firm melt-freeze surface that is quite stable, minimizing our concerns of deeper slab releases. The unique characteristic of this storm, with a lack of strong wind transporting newly fallen particles, is that conditions will be more consistent than is typical across our forecast areas. With well-connected paths, avalanches could be large and in unexpected places. Additionally, be aware that non-avalanche hazards, like rocks and potentially open water that have recently melted out, will likely lurk just under the surface. Cautious travelers will avoid our steepest terrain and seek wind-sheltered areas to enjoy this new snow.

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 Harvard Cabin.

Posted 8:20 a.m., Saturday, April 1, 2017. A new advisory will be issued tomorrow.

Frank Carus/Ryan Matz, Snow Rangers
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856