Avalanche Advisory for Saturday, 4-6-2013

This advisory expires at 12:00 midnight tonight.

Tuckerman Ravine has MODERATE and LOW avalanche danger. The Sluice, Lip, Center Bowl, and Chute 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.

Huntington Ravine has LOW avalanche danger. Natural avalanches and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

Looking for a pleasantly warm spring skiing experience? Sorry, but you won’t find it in Tuckerman today. So how about soft smooth windblown powder? Nope, you’ll have a difficult time finding that here as well. Today is going to be a cold and blustery day on Mt. Washington. To start the day, temperatures are below zero Fahrenheit (-20C) and winds are gusting over 80mph (130kph). As the day progresses, conditions are expected to improve slightly, but I don’t expect anything better than a cold windy day. Not to minimize the dangers posed by avalanches, but I see the potential for cold injuries and falls in steep terrain to be the more probable ways for one to get hurt today. Bring an ice axe and crampons for traveling in the steeps, you’ll be happy to have them.

We took advantage of yesterday’s intermittent sunshine to explore several areas of Tuckerman and Huntington. Overall we found good stability in most areas, though for different reasons in different locations. Some spots had been blown clean down to hard old surface. Other areas had windslab that was smooth and very hard. The thickness of the hard slab varies, in some places you can kick through it with effort and in others you’ll need to go deeper than a meter to get through it.

Avalanche danger today results from a mix of the “difficult to trigger but dangerous” hard slabs that we were looking at yesterday, and the small amount of new snow being blown in this morning. Only about a half inch (1.5cm)was recorded at the summit, but down at Hermit Lake there was a consistent 1″+ (4cm) blown across the snowplot. While these amounts may be laughable to Westerners, we know here that these can add complexity to existing stability problems. In many areas we suspect the new snow has blown clean off the slopes, but it may have stuck in some of the most sheltered lee areas and developed into unstable slabs. These may be smaller pockets in isolated areas or relatively thin slabs in more open slopes such as the Lip and Center Bowl. In the Lip yesterday, there was a deep hard slab layer with additional slab on the surface (test results here were: CT20Q2 at 20cm deep, 1F+ over 1F-; CT29Q3 at 120cm deep). My overall impression of the older slab here is that it would be possible for a person to trigger an avalanche, although on the lower end of the spectrum edging closer to unlikely. The more these slopes are tested and the harder the impacts they see, the greater the likelihood of someone acting as the trigger. A thin slab triggered here could provide the hefty force necessary to step down into deeper layers. If the slope fails deeply it will be a large avalanche with serious consequences, not only to the person triggering it but also to anyone standing in the runout of the path. Lunch Rocks and the floor of Tuckerman are in the runouts of these avalanche paths!

Please Remember:

  • 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 at 7:35a.m., April 6, 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

2013-04-06 Print friendly