Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger today. The Lobster Claw, Right Gully, Sluice, Lip, and Center Bowl have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. The Chute, Left Gully, Lower Snowfields and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The Little Headwall has Low avalanche danger. Natural and human triggered avalanches are unlikely.
Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger. North Gully, Damnation, Yale, and Central Gully have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Pinnacle, Odell, and South have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Escape Hatch has Low avalanche danger. Natural and human triggered avalanches are unlikely.
Another day of flat light and reduced visibility due to fog and snow showers will make assessing avalanche terrain challenging today. Our snowpack remains complex and will demand careful evaluation due to continued wind loading in the gullies with a more southerly aspect and cross-loading in easterly facing areas like Central Gully, the Lip and Center Bowl. Existing windslabs from previous days still exist as well, so be on the lookout for these slabs which are adhering poorly to the suncrust beneath on southerly aspects. Areas with a southerly aspect also have the most developed wind slab from 2.6” of snow that fell yesterday and a total of 5.4” in the past 4 days. That snow was transported on winds gusting to 70 mph and averaging 41.3 mph yesterday. These wind speeds are higher than they have been over the previous several days when wind speeds averaged 23-29 mph. We can expect snow to have been moved into the tops and midsections of gullies rated at Considerable. Whether or not the gullies reach that rating depends on today’s new snow. Field time today will hopefully nail down more exactly where the instabilities lie. For now, we are teetering on the brink of Considerable.
There is some uncertainty about the amount of snow that was recorded on the summit actually having fallen on the Cutler River drainage side. We recorded a 1-7 cm drift at the Harvard snowplot with an average of 3cm at the Tuckerman plot. Clearly enough light snow was available from previous days around the mountain to be carried by yesterday’s winds. If the forecasted snowfall for today reaches the higher amount of 2”, natural avalanches will become more possible and human triggered avalanches will become more likely. Remember that the Moderate rating still requires careful snow and terrain evaluation due to the existing complexity in our snowpack. Buried suncrusts exist which have continued to erode in strength due to cool temperatures, a relatively thin layer of snow above and, curiously, no rain or super high winds to wreck it all. Don’t be fooled into thinking that the rocks and bushes in gullies will serve as anchors. The snow layers in these locations are thin and weak enough that thin spots, such as protruding rocks and bushes may serve as trigger points in the windslab.
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 8:25 a.m., March 5, 2013. A new advisory will be issued tomorrow.
Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forests
(603) 466-2713 TTY (603) 466-2856