Avalanche Advisory for Tuesday, April 3, 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: Isolated, small, and easily avoidable pockets of wind slab exist in the terrain, but long sliding falls will likely be of greater concern for backcountry travelers today. Snowfall and increasing wind late today will add to our wind slab avalanche problem. Avalanche danger will increase slightly after dark today, though any new and unstable slabs that may develop should be small and still best characterized by a Low danger rating. Remember that “Low” does not mean “No” avalanche, and continue to make your own observations for potentially unstable snow on isolated terrain features.

A refrozen snow surface which is hard and icy dominates our terrain, necessitating skilled crampon and ice axe travel on snow slopes. This surface snow will likely not see any softening today. The recent melt/freeze conditions also can result in ice dams, or pressure buildup of flowing water beneath ice, in many of our climbs. A tool, screw, or foot placement can rupture an ice dam. These hazards have been the culprit of serious accidents in past seasons.

 WEATHER: The current overcast skies should persist through the day ahead of an approaching storm system which should bring precipitation starting late today and continuing through tomorrow. Our terrain should initially receive an inch or two of new snow before sleet and even rain mix in by late tonight or early tomorrow. Wind from the S and SW will steadily increase to peak early tomorrow with gusts nearing 100 mph. Temperatures will increase in the same period from the current 12F on the summit towards a high of around 40F tomorrow. Precipitation should taper off as temperatures descend sharply towards 0F on the summit by tomorrow night.

SNOWPACK: Recent melt-freeze cycles have resulted in a layer of refrozen hard snow at the surface that shouldn’t soften today. Beneath this layer, our snowpack still holds dry and firm snow that varies in height but seems to be up to several feet thick. This dry snow lies on the robust January melt-freeze crust we’ve repeatedly referenced this season, on which a thin layer of facets has also been observed. All this means that our currently unreactive and generally stable snowpack continues to have a dynamic, winter-like nature. It’s hard to say yet if the warming temperatures and mixed precipitation totaling approximately ¾” of water that is inbound for tomorrow will result in deep stability concerns. We’ll provide more detail in tomorrow’s advisory, but the weather will likely convince you to avoid travel in the alpine tomorrow regardless. Conditions today will better suit climbers than skiers, with refrozen snow providing good crampon purchase but less than ideal ski conditions. The Sherburne ski trail still has good coverage but challenging snow conditions.

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The Harvard Cabin is now closed for the season. The only place to camp in the Cutler River Drainage is at Hermit Lake Shelters.

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.
• Posted  7:40 a.m., Tuesday, April 3, 2018. A new advisory will be issued tomorrow.

Ryan Matz, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2858

2018-04-03