Avalanche Advisory for Sunday, March 18, 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: Areas of visibly smooth wind slab are our primary avalanche problem today. Moderate rated terrain holds the largest and most continuous of these newly formed slabs which primarily exist in the lower half of our forecast areas. Expect these slabs to be stubborn to touchy though fairly hard, making human triggered avalanches possible and natural avalanches unlikely. The mostly wind textured snow dominant in the rest of our terrain is certainly harder still. It’s important to always remember that “Low” avalanche danger does not mean “No” avalanche danger as pockets of more reactive and softer snow can be found in Low rated terrain. Visibility should facilitate your ability to choose safer travel options, but remember that the cold temperatures and strong wind would elevate the consequences of any accident today.

 WEATHER: Wind has been the dominant factor in our snowpack development in the past 24 hours, blowing out of the W and gusting up to 122 mph on the summit yesterday before shifting NW and decreasing last night. A half inch of new snow was recorded on the summit and a trace at Hermit Lake. NW wind should continue through the day in the 40-50 mph range with a slight increase by tonight. Cold temperatures, with the mercury dipping to -14F on the summit overnight, will continue today and tonight with a summit high just above 0F. No precipitation is forecast today or tomorrow and minimal clouds should allow for good visibility. Wind and temperature should remain consistent through tomorrow night as well, with high temperatures a handful of degrees warmer tomorrow.

SNOWPACK: Gone are the widespread soft wind slabs of a few days ago, as two days of classic Mount Washington wind has hammered our upper snowpack. Expect a high degree of spatial variability in surface snow, from hard and wind textured sastrugi to areas of recently formed and somewhat softer wind slab which will vary in size but could be quite thick. Areas of most concern for instability today are relatively low in our avalanche paths. Avalanche paths have significantly developed with recent storms, and we’re seeing evidence of a widespread natural avalanche cycle in both ravines which likely occurred late last week. The general feeling this morning is, “Wow, there’s a lot of snow!” Take advantage of good visibility to help you identify features of concern as you enjoy the mountains today.

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., Sunday, March 18, 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