Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. The Sluice, Lip and Center Bowl have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Dangerous avalanche conditions exist. Careful snowpack evaluation and conservative decision making is essential. The Lobsterclaw, Right Gully, Chute, Left Gully, and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully to identify features of concern. The Lower Snowfields and the Little Headwall have Low avalanche danger.
Huntington Ravine has LOW avalanche danger. Natural and human triggered avalanches are unlikely except in isolated features of strong lee pockets. These areas can be found in some approaches to climbs and below steep features like ice bulges and rock bands. These pockets do exist.
So far 2013 has come in like a Lion with high winds and some of the coldest temperatures of the season. Tuesday night winds peaked over the century (160kph) mark from the NW and the mercury plummeted to –18F (-28C). It gets colder around here, but man that’s cold! Light snow continues to fall, which added up to 1.8” (4.6cm) on the summit as of midnight. This has generated a veil of snow and clouds over the mountain limiting the use of visual clues for assessment or route finding. It’s important to be conservative under these conditions because you cannot see what’s above you and what new loading may of occurred. All you can go on is weather data, your familiarity with the terrain and what was present before the cloudy cloak was draped over the terrain.
Huntington is at low avalanche danger today because of a brief glimpse we got of the Ravine yesterday and our historical knowledge of what occurs with high NW winds. Very high winds between 90 and 100 mph during the overnight and limited new snow are the two bulls-eye data factors for us to make a low danger call in Huntington. The Ravine’s gullies react very predictably to high winds around 100mph, namely… scouring. The terrain above these gullies and the narrow shape to the couloirs cause rapid wind acceleration generating intense erosion of existing snow. These winds also inhibit new snow from sticking. However, each wind event is slightly different from those of the past so it’s important to expect some slightly unique conditions from each incident. The depth of the air mass affecting the mountains, the exact degree on the compass rose wind is coming from and how gusty the episode all factor in to the final loading situation. Therefore, under a low danger rating expect isolated pockets to be present. Typically they can be found under steep sections of ice such as the bottom of Pinnacle and Odell as well as the approaches to other gullies. The occasional strong lee pocket under prominent terrain features also allow new pillows to form. So the take home message in Huntington is although you will find mostly scoured conditions keep your mind looking for isolated instabilities. In Tuckerman, as is often the case, we believe we have a different scenario playing out. Granted, you will find scouring and wind packing in the usual places from high NW winds such as low in Left Gully and the below the Chute you can anticipate more variability across the entire Ravine. Loading of new snow continues this morning in the strongest lee areas dominated by the Sluice, Lip and Center Bowl. These locales are posted at Considerable due to the potential for natural avalanches being possible. Areas on either side of these SE aspects are posted at Moderate where you can find new instabilities in the deposition, but at a more diminished level.
The freight train of wind will gather steam again this afternoon sending velocities into the 90’s (145kph) again after the short reprieve this morning. Temperatures will fall again to -15F (-26C) and is currently dropping from a brief warm up to about -10 F (-23C). It’s definitely another nasty full arctic day above treeline. Be prepared with the best mountaineering clothing and experience to venture there safely
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 8:30, Wednesday 1-2-2013. A new advisory will be issued tomorrow.
Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856