Avalanche Advisory for Friday, March 9, 2018

Huntington and Tuckerman Ravine have MODERATE avalanche danger. All forecast areas have Moderate avalanche danger. Heightened avalanche conditions exist. Evaluate snow and terrain carefully. The Little Headwall has Low avalanche danger with pockets of unstable snow, ice and holes in the snowpack.

AVALANCHE PROBLEM: East winds gusted to 66 mph on the summit yesterday and cross-loaded lee terrain features and scoured other areas of our terrain. A brief period of visibility yesterday allowed a view into Tuckerman Ravine and showed lots of old gray ice crust showing once again. This is an indication of what occurred in Huntington Ravine where you will likely find old surface either showing or just below new snow. This mix of scouring and deposition of new snow in the terrain makes natural avalanche activity unlikely but human triggered avalanches possible. Move one at a time today when poking into new snow and keep an eye on what or who is above or below you. Visibility will be challenging with flat light and snow showers making assessment and safe travel techniques more difficult. New wind slabs are likely to be largest in Lobster Claw and Right Gully and the northern gullies in Huntington due to their lee position. Hillman’s appears to have a more widely distributed 8″ (20cm) storm slab with less wind effect and fair to good stability.                     

WEATHER: Hermit Lake snowplot received 4.3” (11cm) more snow yesterday with 11.5” (29cm) total for the storm. ENE and NE winds, in the 50 mph range on the summit, prevailed during the most intense periods of snowfall night before last. Wind then shifted north yesterday but diminished to the point that not much snow was transported into our terrain. Right now, wind is light and variable. Be on the lookout for signs of wind transport in the afternoon as wind picks up to the 20-35mph range. Northwest winds tonight will ramp up into the range capable of building larger and more dangerous wind slabs. If you have weekend plans that include being in avalanche terrain, know that the forecast wind speed and direction will raise the avalanche danger tonight and tomorrow and build potentially touchy wind slabs in terrain downwind of a northwesterly. 

SNOWPACK: As you may already know, our record warm February brought stability deeper to the snowpack in our terrain. Unfortunately, the ice crust at that surface has been resistant to bonding with new or wind transported snow. This storm seems no different, despite starting out on the warm side. There is no doubt that snow from this storm found purchase in enough areas to cause stability concerns. You’ll want to bring the full arsenal of avalanche rescue equipment and more importantly your snowpack assessment and terrain management skills today, if you choose to get into the terrain. There is uncertainty in the stability of the areas of wind slab that exist in the terrain but the icy bed surface, total snowfall and flat light should prompt a solidly focused level of situational awareness as you move into the terrain.

There is good skiing and riding to be had on the John Sherburne Ski Trail.

• 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 8:0 a.m., Friday, March 9, 2018. A new advisory will be issued tomorrow.

Frank Carus, Lead Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856