Avalanche Advisory for Wednesday, March 21, 2018

Huntington and Tuckerman Ravines 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 widespread and firm wind slabs formed late last week are becoming generally unreactive as they gain stability. Isolated and softer pockets may still be touchy to a human trigger. Also consider that solar warming, which could occur today before cloud cover increases, has potential to decrease stability of existing slabs. Low avalanche danger means that both natural and human triggered avalanches are unlikely, but that doesn’t rule out avalanches as a potential concern for your mountain travel. Continue to pay attention to the snow you’re travelling on and plan to travel, looking for signs of instability to identify the isolated pockets that may remain touchy to a human trigger. Travelling one at a time in avalanche terrain is still wise with avalanches unlikely but not impossible.

 WEATHER: High cloud cover will increase through the day following yesterday’s clear skies and moderate summit winds. It’s currently nearly calm on the summit, with easterly wind speeds under 10 mph. This wind will increase through the day, ultimately shifting NE and exceeding 50 mph tonight. The high temperature on the summit should be near 20F. This unsettled weather is the result of yet another Nor’easter, though this system is forecast to largely miss the Presidential range. Snowfall which will begin late tonight and continue into tomorrow could total anywhere from 2-6” as wind eventually shifts N and gusts to around 80 mph.

SNOWPACK: Successive storms late last week built an upper snowpack of layered wind slabs on an old melt/freeze crust. These generally firm slabs are gaining stability and becoming unreactive, though isolated pockets that you could still trigger do exist. It’s worth considering that wind slab is a spatially variable avalanche problem by nature as you choose and move through terrain today. Our snow surface is a mix of smooth and wind textured firm wind slab with the scattered pockets of softer slab that pose a greater stability concern, and is providing enjoyable conditions for skiers and climbers alike. This morning looks to provide a continued nice weather window to enjoy the mountain before clouds and wind increase later today.

The Harvard Cabin will be open all nights this week.

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 8:00 a.m., Wednesday, March 21, 2018. 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