This advisory expires at 12:00 midnight, January 21, 2013
Tuckerman Ravine has Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The only exceptions to this 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. 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.
Yesterday was a classic example of how quickly weather can change. It was sunny, warm, and calm in the early morning, then, in an instant it turned into full-on winter conditions. Snow came heavily for a brief period as a cold front swung through. This system brought about 2” (5cm) of new snow and quickly pushed wind speeds in excess of 100mph at times and gusted over 90mph (145kph) on the summit for 6 consecutive hourly observations. After the frontal passage, winds remained strong (65-80mph/105-130kph from the west) while temperatures began to plummet. This morning is a brisk one; temperatures at Hermit Lake are currently -2F (-19C).
In Huntington, most of the new snow was pushed down through the gullies and is now lying in the woods below the ravine. The only snow that didn’t get transported out of avalanche terrain either was exposed to the winds, and therefore was hammered down into a firm, strong surface, or it was able to find a protected lee area where it could escape the punishing winds. In these protected lee areas you will find the greatest instability and have the best chance of triggering an avalanche. Pinnacle and Central Gullies both have enough terrain that fits this description to warrant a Moderate rating. In other areas rated Low, be suspicious of any pocket of snow that allows any boot penetration. The best stability will be found either on exposed old crust or on deep, stiff windslabs. Additional snow is blowing around the ravine, but appears to be having difficulty sticking and forming new slabs. Expect the tops of some climbs, e.g. Yale, Damnation, and North, to be scrappy. There is just not very much snow in there at this time.
As is often the case with strong winds, Tuckerman Ravine as a whole is responding similar to the protected lee areas of Huntington. There is much less of a scouring effect here than in Huntington. We’re starting the day with a range of conditions that all fall within the Moderate rating. The areas of most concern are the Sluice, Lip, Center Bowl, and Chute. (if you’re a regular reader of the advisory, this information should not be a surprise to you.) Currently windblown snow is keeping us near the upper end of the rating. The rate of loading should slow today as wind speeds continue to decline, but remember that cold temperatures tend to make newly developed slabs fairly “snappy.” That is to say that the potential for a slab to propagate a fracture does not diminish as quickly as it would on a warmer day. Outside of the middle of Tuckerman, you’ll find a mix of surfaces. Expect some old crust to be exposed in Right Gully, Lobster Claw, and the lower portion of Hillman’s Highway. In Left Gully and the top of Hillman’s you’ll find more strong wind-effected snow. As with Huntington, pay attention for softer areas that were protected from the strong winds. Thick, stiff slabs and exposed old crust are your best bets for stable snow.
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 8:25am, January 21, 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