Avalanche Advisory for Friday, February 16, 2018

Huntington and Tuckerman Ravine have LOW avalanche danger. All forecast areas have Low avalanche danger. Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

AVALANCHE PROBLEM: The warm spell yesterday and last night brought another period of settlement and melt. The snowpack has already been through above freezing temperatures earlier in the week and warm temperatures returned yesterday and remained overnight. In general, we feel that weaknesses in the snowpack have already been tested by the previous warming but we can’t discount the potential for further warming to cause concerns this morning. If you are out and about in the terrain early, keep the potential for wet slabs and especially wet loose avalanches on your radar along with the potential for rock and icefall. The hangfire in the Lip remains a concern given the steep rock slab that the massive, serac-like feature sits on. Any of the steep gullies in Huntington Ravine, especially the generally rocky and loose northern gullies, would have me searching for sheltered belay nooks. Surface conditions are changing rapidly as colder temperatures return and refreeze surface snow. Two inches of new snow may fall late in the day and may lead to minor sluffing.

WEATHER: Temperatures in avalanche terrain spent much of yesterday above freezing. Hermit Lake started Thursday at 28F and recorded a high of 38F. Wind remained from the W, dipping into the 20 mph range early and gusted to 80 mph yesterday evening. Currently, the Summit is at 25F and Hermit Lake is at 35F. The incoming cold front will keep temperatures decreasing with the sharp drop happening after noon, allowing lows to go below zero F on the summit tonight. Wind will shift to the NW and increase to the 50-70mph range later in the day. There is a chance of snow in the forecast with up to 2” possible by midnight tonight.

SNOWPACK: As mentioned in the avalanche problem section above, the past 24 hours of warming is the second one this week. Sunday and Monday brought a little under a quarter inch of rain and high temperatures of 36 F and 34 F, respectively, totaling 16 hours above freezing temperatures on the summit with even more in our lower elevation forecast area. That warming trend was followed by seasonably cold temperatures that refroze layers near the surface and led to reduced concerns for existing wind slab avalanches. The warmth yesterday and overnight softened surface snow. Very steep areas, or slabs of snow on ice or areas with running meltwater will remain a concern until refreezing occurs. As temperatures drop today and overnight, any free water in or under the snowpack may form ice dams late today or more likely tomorrow. Any off-trail travel will be difficult early today due to the weakened snowpack which likely won’t support your weight. Due to the icy conditions, micro-spikes will be useful with crampons, ice ax and the ability to use them effectively a key element in any above tree-line travel plan.

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 8:10 a.m., Friday, February 16, 2018. A new advisory will be issued tomorrow.

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

2018-2-16