Avalanche Advisory for Friday, April 14, 2017

This advisory expires at Midnight.

Huntington and Tuckerman Ravines have LOW avalanche danger. Natural and human triggered avalanches are unlikely. Generally safe avalanche conditions exist, but watch for unstable snow on isolated terrain features. The Little Headwall is not forecast as it is now dominated by flowing water, but will still hold weak snow bridges and other undermined snow hazards.

 AVALANCHE PROBLEM: Over the past 36 hours, our snowpack has undergone a significant refreeze. This limits today’s primary avalanche problem to loose-wet sluffs that a human could initiate on sun-softened steep slopes. This morning, our relatively uniform snowpack has a quite firm surface that should soften nicely by this afternoon in areas of prolonged sun exposure. Be aware that terrain seeing less softening will hold a firm and smooth surface and easily provide the opportunity for a long sliding fall. Additionally, a refreeze will occur this evening, which can return softened snow to a firm sliding surface with a surprising quickness.

 WEATHER: It’s a nearly cloudless blue sky morning on Mount Washington, and forecasts suggest it will remain so all day today. Temperatures, limited to 20F on the summit yesterday and last night, will rise steadily through this afternoon and reach a high around the freezing mark, with slightly higher temps in our forecast areas. Wind will blow steadily from the NW near 30 mph on the summit, which should feel relatively calm low in Tuckerman or Huntington.

Temperatures in the low to mid-thirties, with clear skies and mild wind, mean that sun exposed slopes could provide excellent spring ski conditions, with snow able so soften but not become overly sloppy. Today is shaping up to be a very fun day of spring turns. However, the spring season brings a set of decidedly non-avalanche hazards:

  • Icefall – This is the time of year when ice climbs fall down as one piece. This is different from early spring icefall that produce small ice chunks that make you glad you wore a helmet. Pieces of ice the size of cars are not uncommon and can accelerate quickly. Huntington Ravine is very active this morning. The ice pillar in Sluice hangs precariously above Lunch Rocks. The Tuckerman Headwall will also start to shed layers too, making lounging in the floor of the Ravine a poor choice today.
  • Long sliding falls – Crampons are highly recommended in steep terrain. Snowshoes and microspikes are no substitute, and the grip your ski edges does have a limit. Arresting a fall on an icy 30+ degree slope can be practically impossible, even with an ice axe. Much of our terrain hold a firm surface prime for this sort of accident. Refrozen snow and this sliding fall hazard come and go with surprisingly minor fluctuations in temperature, wind and cloud cover.
  • Crevasses or glide cracks, moats and waterfall holes – Warm water flowing under the snow pack creates holes and thin spots in the snow surface that are deep enough to injure or kill you. New snow can drift and obscure the openings.

The Harvard Cabin is closed for the season. We will continue posting advisories there as long as it is logistically feasible or until the ice melts out and we move to a General Bulletin.

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 caretaker at Hermit Lake Shelters.

Posted  8:15 a.m., Friday, April 14, 2017. A new advisory will be issued tomorrow.

Ryan Matz, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2017-04-14