Expires at 12:00 midnight, Saturday 1-8-2013
All forecast areas of Tuckerman Ravine have Moderate avalanche danger today. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully and identify features of concern. The only exceptions to the Moderate rating are the Lower Snowfields and Little Headwall which have Low avalanche danger. Natural and human triggered avalanches are unlikely.
Huntington Ravine has Moderate and Low avalanche danger. North, Damnation, Yale, Central, and Pinnacle gullies have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Odell, South, and the Escape Hatch have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.
Last night I went to sleep hoping that the wind forecast for Mt. Washington would be wrong, that speeds would stay where they were and not ramp up to 80mph (129kph). Sadly, around 9pm they started to increase, and are currently blowing from the W at 75mph (121kph) gusting to 90mph(145kph). This is a big deal because it changes what we saw in the field yesterday into something quite different. In the bowl yesterday we found a moderately stable, rightside-up snowpack. There were numerous layers sitting on top of the Dec 21st rain crust, but one consistent feature was the most recent 1.8″ (5cm) of snow had blown into a 2-3″ (5-7.5cm) deep, fist-hardness soft slab sitting on the surface. Beneath this was a layer of 4-finger hardness slab, and beneath that was a thick layer of 1-F hardness with a very thin weak layer of gently preserved snow crystals sitting in the middle. At that time, I would have told you stability fell in the Moderate range, with some locations being at the lower end of the rating (e.g. Lobster Claw or Right Gully) and some being at the upper end (e.g. closer to the Lip and in the Sluice). Unfortunately, early this morning the winds began to move more forcefully, picking up additional snow from the alpine zone, and burying the soft surface layer beneath a denser, harder slab. This will effectively flip the snowpack from rightside-up to upside-down, with stronger snow above weaker snow. Most importantly to you is that it makes it more possible that you’ll trigger a smallish surface slab, and the energy from that has the potential to step down into deeper layers. Based on the effect of these winds, I now feel that the stability today will be pushing the limits of the Moderate rating in areas such as the Lip, the Center Bowl, and maybe even Central Gully in Huntington. One question that my crystal ball refused to answer is just how much snow will be available for loading when winds begin to diminish. If the answer is that a lot is still able to be transported into the ravines, we may even exceed the forecasted ratings due to the possibility of natural avalanches.
In Tuckerman, getting to the Little Headwall is a thick bushwack with lots of open water. The Lower Snowfields have so little snow in them that I can’t imagine why anyone would try to travel there. Hillman’s and Left Gully had a lot of wind scouring prior to the increase in loading this morning, so they fall in the lower end of the Moderate rating. Over in Huntington, Escape Hatch is not recommended for travel unless you really, really enjoy bushwhacking downhill over spruce traps. South, Odell, Yale, and Damnation had a good amount of wind scouring with pockets new snow in isolated areas. New wind loading may make these areas larger and more unstable. Stay alert to what type of snow you’re traveling on, and stick to hard old surface when possible. Of all the gullies in Huntington, Central had the most new slab. The approach to the ice bulge and just above the bulge are examples of where you should be most vigilant.
We have opened the Lion Head Winter Route for the season. This is a steep mountaineering route, and we strongly recommend bringing an ice axe, crampons, and the ability to effectively use these tools.
- 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 6:45am, January 8, 2013. A new advisory will be issued tomorrow.
Jeff Lane, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856