Tuckerman Ravine has MODERATE and LOW avalanche danger.The Sluice, Center Bowl and the Chute have Moderate avalanche danger today. Natural avalanches are unlikely and human triggered avalanches are possible. Heightened avalanche conditions exist on specific terrain features. All other forecast areas have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features.
Huntington Ravine has LOW avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features.
We are starting day three of warm spring-like weather here at Hermit Lake at 51 degrees! The undercast and cooler temperatures in the valley may not be conveying a clear picture of what is going on here. We’re melting. The winter wonderland that was our landscape for the past several weeks has been replaced by early signs of spring. The fir trees shook off their mantles of snow and rime ice yesterday as sunny skies allowed temperatures to climb again into the high 30’s with light to moderate SW winds on the summit ridges. Heating of the snowpack has occurred slowly enough over the last few days that the snowpack didn’t shed needed layers of snow in natural avalanches. In fact, we only saw the one unintentional skier triggered avalanche in Right Gully on Saturday morning and one small naturally released sluff from above the ice in the Sluice. In retrospect, though we had weak interfaces that produced easy shears in the top most interfaces as well as on last Tuesdays pooled graupel, the strength of the over lying slabs and their reluctance to propagate a crack as well as the discontinuous nature of the weak interfaces and layers held the snowpack together. Good news for climbers and skiers, bad news for fans of avalanche phenomena.
There are still some cold slabs out there which didn’t gain much heat yesterday due to their shady location, diminished slope angle or exposure to the wind. These areas, which hold some of our greatest concerns moving forward, also saw no skier or climber traffic to test the slope and chop up the slabs. Yesterday afternoon, I took snow temperatures in various locations on the south aspect of Tuckerman Ravine to try to nail down the extent to which the sun’s heat was penetrating the snow. Remarkably, I found temperatures 20cm down at -3 to -4 C even though in many of these same locations surface snow was in the damp to wet range. Also, surface temps on the rollover at the tops of Right Gully and Lobster Claw were all still cold hard slabs. The Chute and the left side of the Center Bowl were shielded from much of this solar gain and contain these same slabs. Though strong, those slabs will weaken through the day today as long as ambient temperatures remain high. One other area that has my hackles up is the upper right portion of Sluice since the slabs there are really steep and saw no traffic yesterday. Keep all these areas in mind when tomorrow’s rain begins to add weight and stress to our snowpack as they may be the first areas to avalanche.
Huntington Ravine doesn’t have the same concerns as the areas I mentioned in Tuckerman due to a lack of large slabs in areas with the northeast facing and steep slope angle. Though pockets of cold slab on steep slopes may have escaped the beating rays of the sun yesterday they exist mainly as isolated pockets. Remember that Low doesn’t mean no avalanche danger so give these steep gullies the respect they deserve since even a small wet sluff can pack a punch.
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 the Harvard Cabin. Posted 8:15 am, March, 11th 2013. A new advisory will be issued tomorrow.
Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856