This advisory expires at Midnight tonight.
Huntington Ravine has MODERATE and LOW avalanche danger. Central, Pinnacle, Odell, South and Escape Hatch have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Heightened avalanche conditions exist on specific terrain features. North, Damnation and Yale have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.
Tuckerman Ravine has MODERATE and LOW avalanche danger. Sluice, Lip, Center Bowl, Chute, Left Gully and Hillmans 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. Lobster Claw and Right Gully have Low avalanche danger. Natural and human-triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features. Lower Snowfields and Little Headwall are not rated due to a lack of snow but look for overhead hazard in Lower Snowfields which remains mostly tree covered except beneath Duchess.
AVALANCHE PROBLEM: Snow drifts at lower elevations are an indication of the wind slabs that exist in both Ravines. The 5” of snow that fell yesterday morning coupled with the 1-2” that fell yesterday were transported by 60-70mph west winds. It is likely that these wind slabs will be firm and stubborn in most areas due to the hammering the snow received from strong winds over the past 12 hours. A trace to 2” of new snow today will challenge visibility and build more small but softer and easier to trigger wind slabs. Wind scouring will continue this morning in the northern gullies of Huntington. Remember to watch for small wind slabs in the Low rated terrain. Low danger does not mean no danger!
WEATHER: West winds at 65-85 mph with gusts to 95 mph will continue to load snow in lee areas of both Ravines this morning. Summit fog will reduce visibility and flatten light making visual clues of wind affect on the snow challenging to pick out. Another trace to 2” of snow will fall today, further loading lee slopes and reducing visibility. Cold temperatures near 0F are on tap for the day as light upslope snow showers continue through today and into the night as a weak low passes the region.
SNOWPACK: Old firm wind slabs remain visible in some areas this morning which serve as indicators that strong winds have scoured portions of our terrain while building wind slabs in others. These older wind slabs from the nor’easter were firm and well bonded to the melt/freeze crust earlier this week. That said, one issue to look for in study pits will be the potential development of facets at the crust interface. The strong temperature gradient created by cold air temperatures drive the faceting process both on the surface and around crusts within the snowpack. These crystals bond poorly with their neighbors and can serve as a weak layer or weak interface. This has not been observed yet but the potential is there as colder temperatures dominate the forecast. New wind slabs formed over the past 24 hours will require careful assessment for safe travel today.
The Lion Head Winter Route is open and the most direct route to the summit. The Tuckerman Ravine Trail bridge is completed enough to allow traffic again. Please be careful of construction debris near crossover 7 on the Sherburne Trail when skiing or riding.
- 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 8:15a.m., Thursday, January 5, 2017. A new advisory will be issued tomorrow.
Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2713