This advisory expires at 12:00 midnight, February 22, 2013.
Tuckerman Ravine has MODERATE and LOW avalanche danger. The Lobster Claw, Right Gully, Sluice, Lip, Center Bowl, and the Chute have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Left Gully, Hillman’s Highway, the Lower Snowfields, and the Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features.
Huntington Ravine has MODERATE and LOW avalanche danger. Central Gully has Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. All other forecast areas have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features
After 3 days of snow and blowing snow that totaled just shy of 10” (25cm) on the summit, we finally have beautiful clear conditions. During the High danger rating on Wednesday we had an avalanche cycle in the Center Bowl and Lip that left a number of fracture lines in its wake. The big question we are dealing with right now is will south faces warm enough today with sun and very low wind to become unstable due to rapid warming?
Over the past 24 hours we have seen 3” (7.5cm) of snow with winds predominately out of the N. Speeds increased from 28mph (45kph) yesterday morning to almost 70mph (113kph) by 7pm (1900hrs). This increasing velocity from the N loaded new snow into Tuckerman’s south and southeast aspects, namely The Lobster Claw, Right Gully, and the greater Sluice area. These newest slabs will be affected by a cooking sun today as clear conditions are expected with a dropping wind from the NE and E perhaps reaching down into the 5-10mph (8-16kph) range. Therefore slopes facing south will see rapid warming which will initially start stabilizing slabs by decreasing their ability to propagate. But then the big question, will heat penetrate deep enough into thin slabs to head us towards instability. I would expect some of these slopes in Tuckerman to move towards the upper end of the Moderate rating this afternoon bumping the ceiling of the definition. Although natural avalanche activity will still be unlikely the steepest most sheltered lee will being inching closer to “possible”. In Huntington the lack of snow makes this solar heating much less of a problem. Damnation and Yale, the biggest south facing slopes in Huntington have mostly scoured slopes, but keep an eye on snow near the top exits. Cornices developed during the last Nor’easter are unlikely to be a problem today due to their long term developing strength but they shouldn’t be ignored. The greater issue nearby, and our number one concern in Huntington, is the bottom snowfield leading to the ice bulge in Central Gully. This area harbors some cold newly deposited slab instabilities.
Back over in Tuckerman cold slab instabilities will also be found on slopes faced away from the south. Between the Chute and Lip which face generally east should hang on to their cold slab properties. A number of crown lines exist in this area from avalanche activity over the past 48 hours. Some of these have been partially reloaded and some steep slopes above fracture lines (hangfire) are still to be respected. As you move high to the Left Headwall and Chute you will find some locations that did not avalanche which makes it likely that some deeper slabs will found in these locations. Overall, it’s a “heads up” kind of day. With this weather and recent snow we expect to see people out moving around on the mountain, so pay attention and be prepared to change your plans if the actions of others warrant doing so.
- 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 8:39 2-21-2013. A new advisory will be issued tomorrow.
Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856