This advisory expires at Midnight.
Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger. Central, Pinnacle, Odell and South Gully have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. North, Damnation, Yale, and Escape Hatch have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.
Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. Sluice, The Lip, Center Bowl, Chute, Left Gully and Hillmans Highway have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Lobster Claw and Right Gully have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Lower Snowfields and Little Headwall are not rated due to a lack of snow.
AVALANCHE PROBLEM: Another 1.4” of snow in the past 24 hours, along with wind speeds that continue to increase, keep natural, wind slab avalanches possible. These wind slabs are likely to be stubborn in most places but could likely be triggered by someone traveling over the right thin spot or weak layer in the slab. These hard slabs could run out pretty far given that a regular series of avalanche cycles has smoothed out and extended many of our avalanche paths. That said, many boulders and cliffs remain uncovered so even a small avalanche would be really unforgiving in areas like Sluice, Lip, Center Bowl and Hillmans whose paths are peppered with boulders. We are teetering on the edge of possibility for natural avalanche activity and may very well be scoured and wind packed into a more Moderate hazard especially by the end of the day.
WEATHER: The temperature will fortunately rebound from where it sits at -35F at 6am. Winds from the WNW in the 70-90 mph range may gust to 105 mph this morning and abate some today and shift a bit west. 50-70 mph later with temperatures in the -15F range will still present plenty of opportunities to freeze fingers while digging your stability test pits and frostbite your cheeks looking for a line around potentially unstable smooth pillows of wind slab.
SNOWPACK: We have a dynamic snow pack right now and have had limited opportunities to move around with an acceptable degree of safety over the last couple of days. We do know a few things based on our snowpack and weather history. Pencil hard wind slabs are likely to be pretty widespread. In some places where they are thick and bridge between gully walls or lower angled terrain they are likely to be unreactive. In unsupported, steeper or convex areas, the strain on the slab combined with the presence of weak layers of rimed particles, or possibly the melt-freeze crust, may yield the right ingredients for a hard slab avalanche. Deep slabs at the base of steep pitches of ice, such as the approach to Pinnacle, have proven to be a problem under similar conditions too. Be heads up if you venture into the terrain since lots of challenges are in play.
The Lion Head Summer Trail remains the better route to the summit. Remember that the bridge work continues on the Tuckerman Ravine Trail so use the detour on the Huntington Ravine Trail. Many people are using the Sherburne as an uphill route; please be on the lookout for these people as well as machinery that is using the Sherburne as the access to the construction site. We hope to reopen the Tuckerman Ravine trail today so look for signs being pulled by FS staff!
- 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 7:30 a.m., Friday, December 16, 2016. A new advisory will be issued tomorrow.
Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2716