Avalanche Advisory for Tuesday, March 20, 2018

Huntington Ravine has MODERATE and LOW avalanche danger. Central Gully has Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern. All other areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.

 Tuckerman Ravine has MODERATE and LOW avalanche danger. Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully to identify features of concern. All other areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.

 AVALANCHE PROBLEM: Wind slab which varies in size and character across the terrain remains our primary avalanche problem. Present in all forecast areas and largest in Moderate rated areas, these slabs should be stubborn to a human trigger but could result in a large avalanche. Cold temperatures which slow bonding between recently formed layers lead us to believe that human triggered avalanches are still possible today, though natural avalanches will be unlikely. Surface snow is fairly firm and supportable in many areas, but softer pockets can be found as well. This spatial variability necessitates careful evaluation of the avalanche problem on your specific route, and that travelling one at a time on and below all avalanche terrain remains appropriate. “Low” avalanche danger does not mean “no” avalanche danger!

 WEATHER: Yesterday’s 60-80 mph NW summit wind has finally begun to diminish. This should continue through the day, possibly to below 30 mph this afternoon. A high of 15F on the summit, compared to -3F yesterday, will combine with slackening winds and generally clear skies to make for a nice day in the mountains. Wind is forecast to shift through N to NE tonight and into tomorrow while increasing slightly. Cloud cover should increase through the day tomorrow, bringing a chance of minimal snowfall late Wednesday and into Thursday.

SNOWPACK: The repeated 100+ mph wind events at the tail end of last week’s storm cycle moved a great deal of snow and left little for our 50-80 mph winds to transport in the past few days. Combined with a widespread natural avalanche cycle, our alpine terrain holds much more snow than it did a week ago. This new snow is generally firm layers of wind slab, with some softer pockets both on and below the surface. These slabs are generally stubborn to a human trigger but are large and well connected in some areas, providing a low probability/high consequence kind of avalanche problem. Particularly cold temperatures which are finally easing today have slowed stabilization of these layers formed at the tail end of last week. Today’s warmer though still below freezing temperatures could result in a brief and minor decrease in stability before ultimately increasing strength of bonds in our upper snowpack. Don’t let your guard down, continue to respect avalanche terrain, and enjoy the milder weather and generally good skiing and climbing conditions.

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., Tuesday, March 19, 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

2018-03-20