8:45 Sunday, 2/20/2011
Tuckerman Ravine has CONSIDERABLE, MODERATE, AND LOW avalanche danger. The Sluice, Lip, Center Bowl and Chute have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Dangerous avalanche conditions exist, therefore conservative decision making is essential. The Lobster Claw, Right Gully and Left Gully have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Hillman’s Highway, Lower Snowfields and the Little Headwall have Low avalanche danger. Isolated terrain features do contain pockets of instability in these Low rated areas.
Huntington Ravine has both MODERATE AND LOW avalanche danger. Central and South gully have 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.
Blowing snow and low visibility were the dominate features through Saturday with some impressive gusting even though winds didn’t get extreme during daylight hours. The air mass was thick, giving us substantial winds all the way to Pinkham Notch. Winds pushed upwards quickly early this morning, gusting to 109mph and getting above 100mph for a few hours. Winds are on the downhill slide but are expected to remain between 75 to 95mph a bit longer subsiding to 50-70+mph later today as a clearing trend begins. We have had a little bit of clearing this morning but the windows were short lived especially in the Tuckerman area with some longer breaks over in Huntington. The high winds over night did their share of scouring as we would expect particularly due to the old surface crust and yesterday’s low density snow. Bonding between these two layers was likely difficult on exposed slopes, but in very protected lee areas from the wind I would anticipate slab with a varying degree of hardness. This is also the case down low in the trees were snow settled once out of the high winds. In Huntington most areas have been highly wind effected and scoured, but in areas posted at “Low” instability may be found in isolated terrain features. The areas of most concern can be found in Central Gully above and below the center ice bulge and near the top of South Gully warranting a “Moderate” rating. In Tuckerman poor visibility is still making it unclear what avalanched, what didn’t, what reloaded, and what is scoured. Down low, good visibility is showing the trees between the Little Headwall and the bottom of Dead End Gully have new soft slab that is worthy of recognizing as an isolated terrain feature within it’s Low rating. This is also the case for high in the climber’s right start zone of Hillman’s Highway. Some areas forecasted at Moderate to highlight is the approach to both the Lobster Claw and Right Gully and the protected lees as you move into these forecast areas. I suspect the potential for human triggers are real in these two gullies particularly the SE and E facing aspects on the climber’s left side. The main area to have unease about is in Tuckerman’s Sluice through Chute forecast areas which have Considerable avalanche danger. These areas have historically generated the largest slab instabilities and avalanches with the weather conditions we have seen over the past 30 hours. Although loading should remain light today these areas have the greatest potential for both natural and human triggered avalanches.
A few things to consider in addition to the previous stability discussion relate to the amount of traffic in the mountains right now. The holiday weekend has brought more people onto Mount Washington than most Saturdays and Sundays which heightens the importance to make conservative decisions. You need to be concerned about you being a human trigger for slabs under your feet as well as those below you that can’t be see through the clouds. Flipping that around as you enter the bottom of gully someone you may not be able to see could be descending in the start zones after ascending from a different location. When it’s busy it is a heads up day with more triggers and more people over and under one another.
- 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.
- This advisory expires at midnight. 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