This advisory expires at Midnight.
Huntington and Tuckerman Ravines have CONSIDERABLE avalanche danger. All forecast areas will have Considerable avalanche danger today. Natural avalanches are possible and human-triggered avalanches are likely. Dangerous avalanche conditions exist. Careful snowpack evaluation, cautious route-finding and conservative decision making are essential.
Lower Snowfields and Little Headwall are not rated due to thin snow cover but look for overhead hazard in Lower Snowfields which remains threatened by the avalanche path beneath Duchess.
AVALANCHE PROBLEM: Due to mixed precipitation, rain and warm temperatures on our snowpack, expect wet slab avalanches to be the primary avalanche problem today. Should they occur, these slab avalanches could certainly be large enough to bury a person in many areas of either Ravine. The likelihood of avalanches today has us straddling the line between Moderate and Considerable but uncertainty about size is a strong concern. Given the weak faceted layers and pooled graupel that are present in our snowpack, a conservative approach seems warranted. Loose-wet avalanches are also likely in the steepest terrain where soft snow blew in 24-36 hours ago.
WEATHER: Two days ago, 5” of snow was recorded on the summit accompanied by high winds and balmy temperatures climbing to 21F. Currently, the summit temperature is 31.5F at 6am with colder air remaining in river valleys as warm air nudges in. Temperatures are around 42F at Hermit Lake early this morning and about the same at Ravine levels. Forecast models are calling for .46” of liquid today with the majority of that falling as rain in the afternoon hours. A cold front will pass overnight when the wind will crank up to around 100mph and temperatures will fall rapidly to the mid-teens F on the summit. A trace to 2” of snow may fall overnight with high wind continuing through tomorrow.
SNOWPACK: A number of crusts of varying porosity and strength exist in our snowpack down to about a meter or so. Currently at Hermit Lake the upper 20 cm of snow has already become wet. Steeper terrain behaves differently but anticipate heat and moisture reaching down into the weak layers in the upper 20-30cm by mid-day. The deepest crust from our last thaw in mid-December has been well bonded to the upper snowpack so it is unlikely to be a player. The old, faceted layers around the near surface crusts, along with the new wind slabs that formed 36 hours ago, are the main concern driving the avalanche problem today. The forecast liquid equivalent and rain is not much of a load to drop on this snowpack but when coupled with a person perforating or loading an already weakening slab, trouble could arise. Careful snowpack assessment and managing your exposure today could allow for a day of rainy alpine climbing or skiing in sloppy snow but, honestly, why would you bother? Expect low avalanche hazard, good cramponing accompanied by variable and likely horrible skiing conditions tomorrow after this mess refreezes. Long sliding falls appear to be the main hazard to manage over the upcoming holiday weekend.
The Lion Head Winter Route is open and the most direct route to the summit. Please be careful of bridge 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 8:00a.m., Thursday, January 12, 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