Avalanche Advisory for Wednesday, February 28, 2018

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

 AVALANCHE PROBLEM: Wet weather today may reduce stability in wind slabs formed earlier in the week, making wet slab our primary avalanche problem today. This problem is isolated to areas of existing wind slab which can be visually distinguished from the hard, refrozen snow also present at the surface. Timing of peak instability depends directly on the type and timing of precipitation in our terrain. Watch for precipitation falling predominantly as rain to result in the greatest potential for unstable snow. If we receive less rain and more frozen precipitation particles, expect lesser instability of existing slabs. Bear in mind that significant portions of our terrain have firm, slick, refrozen snow at the surface. The risk of a long sliding fall that would be near impossible to arrest may be of greater concern than an avalanche today. Also remember that “Low” avalanche danger does not mean “No” avalanche danger.

 WEATHER: Unsettled weather returns today after sunny and below freezing conditions yesterday. Forecasts are trending towards mixed and wet precipitation that will develop through the day. It appears that the snow level today will be around 5000’, above which a trace to 2” of snow is expected. This translates to modest amounts of moisture falling as rain, freezing rain, sleet, and maybe a little snow in our terrain which is mostly below 5000’ in elevation. This snow level could push up or down and affect the type of precipitation we ultimately see, affecting avalanche conditions as mentioned in the Avalanche Problem section. Mixed precipitation will continue tonight, possibly trending more towards snow, and taper off by tomorrow. Wind will be westerly and peak early today with gusts up to 80 mph on the summit, diminishing this afternoon and tonight.

SNOWPACK: The surface wind slabs formed earlier this week alternate with exposed refrozen snow to make up the surface in our terrain. A series of melt/freeze events has eliminated concerns of deeper instabilities for the time being. These pockets of wind slab that will become less stable with wetting through the day vary in size and character across the terrain. Areas receiving most solar warming yesterday will even hold a sun crust this morning. Pockets of surface snow instability which may increase today suggest that you should not let you guard down, but risk of long sliding falls on the slick snow absent of today’s avalanche problem should be respected as much or more. Two individuals took such falls this past weekend. Both were lucky enough to escape with injuries allowing them to walk out, but such close calls remind us that steep, icy snow slopes demand respect.

The John Sherburne Ski Trail remains mostly snow covered though holds sections of exposed ice and thinly covered rocky ground. It is mostly skiable, but expect sections of challenging variable conditions.

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, February 28, 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

2018-2-28