This advisory expires at 12:00 midnight, January 14, 2013.
Tuckerman Ravine has Considerable and Low avalanche danger. The Sluice, Lip, and Center Bowl have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. All other forecast areas have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features. This is an unusual day as far as avalanche potential goes, so please read on for details.
Huntington Ravine has Moderate and Low avalanche danger. Central Gully and Pinnacle Gully have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. All other areas have Low avalanche danger. Natural avalanches are unlikely except in isolated terrain features.
Well, it sure is an interesting morning to be an avalanche forecaster. Hermit Lake is hovering just shy of 50F (10C) right now with thick fog up in the ravine. It’s been this way since early last night, and temperatures have been above freezing in the ravines since Friday. Yesterday, I thought we might escape without too much damage to an already thin snowpack, but the difference between yesterday and this morning is significant. The Cutler River leading out of Tuckerman has opened up completely and the Little Headwall is now a torrent of falling water. Today, temperatures will begin to fall back into normal winter numbers. The summit temps should go below freezing late morning and the rest of the mountain will follow in the early afternoon. This will begin a process of freezing the saturated upper layers of snow, but this process will take some time. Until then, we will continue to have free water within the snowpack percolating downward, finding small channels, and working its way into larger streams.
Today’s biggest avalanche problem is the potential for water in these streams to rise up into the snowpack and release wet avalanches. These may be wet slabs or loose wet avalanches, but either can be very dangerous due to their incredible mass. The locations where streams tend to flow all year and drain larger areas of the terrain hold the greatest potential for streams to exceed their capacity and overflow into the snowpack. The best examples of where we might see naturally triggered wet avalanches include the Lip, the Center Bowl, Sluice, Pinnacle, and Central Gully.
The avalanche potential in the rest of the forecast areas is lower than in these five slide paths, but remember that Low danger does not mean no danger. In many of these areas, there is less snow overall and less water draining down the gullies. I believe the probability that we’ll see avalanche activity here is at the level where “unlikely except in isolated terrain features” is the best way to describe the problem. The snowpack has already weathered a prolonged period of warm weather, so many of the potential weak layers have already been tested. Look at locations with pockets of deeper snow to be the ones that maybe have not been fully tested. Examples where I’d be on the lookout include the lower portions of the gullies in Huntington, also up high in Hillman’s and Left Gully, and in the mouth of Right Gully.
Ok, moving on from avalanches…today the mountain will begin to freeze up. Once this happens, conditions on steep snow will become treacherous. A slip, trip, or fall in steep terrain will need to be arrested immediately, and depending on how hard the crust sets up, this may be nearly impossible for even the most skilled mountaineer. Over the years we’ve seen enough of these lightning fast long sliding falls to know that they are not something to take lightly. Consider your terrain choices carefully this upcoming week. There are currently few locations where the runout of a long fall does not involve significant consequences.
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 8:45am, January 14, 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