This advisory expires at Midnight.
Huntington Ravine and Tuckerman Ravine have LOW avalanche danger. Natural and human-triggered avalanches are unlikely in all forecast areas. Watch for unstable snow on isolated terrain features.
AVALANCHE PROBLEM: A few things to look out for today are areas of Wind Slab as well as the possibility of a Wet Slab. As the day progresses, the chance of a human-triggered wind slab will decrease as the snowpack warms, however this will increase the chances of a wet slab. Pockets of wind slab are isolated and are identifiable by their smooth appearance; they are primarily in the steeper terrain and in lee areas of NW winds. Areas of greatest concern for a wet slab today would be areas that have not seen much traffic and will bear the brunt of the sunshine today. The Sluice fits this category well and also has the added objective hazard of icefall potential today. With warming temperatures, it doesn’t have to be spring to have springtime hazards. Be aware of icefall today and also be on the lookout for settlement cracks beginning to appear.
WEATHER: Warm temperatures, calm winds, and sunshine will dominant the weather for today. Yesterday, the Summit recorded a high temperature of 36F with ample morning sunshine. Currently, it is 30F on top and 37F at 4000’ Temperatures will increase today with some areas likely getting into the 40sF. Winds are currently 33mph from the west and will decrease further along with clearing skies. It will remain warm tonight, likely with much of the mountain remaining above freezing.
SNOWPACK: Overall, our snowpack is stable to start the day. Several slopes, primarily the south-facing slopes like Right Gully, Lobster Claw, Yale, Damnation, and North have experienced some freeze/thaw cycles over the past few days. The warmth has yet to penetrate deep into the snowpack, leaving cold snow beneath the top several inches which are undergoing the daily change. East and north facing slopes, Lip through Left and Central through South have remained primarily unaffected by the diurnal temperature fluctuations. These slopes are made of mostly one-finger to pencil hard snow of varying forms: wind slab and sastrugi interspersed with small pockets of the softer wind slab of concern today. With ambient air temperatures reaching into the upper 30sF along with clearing skies, many slopes will feel significant warming today. While this will help soften the snow and in areas make good traveling, S and SE facing slopes and mini-bowls like the Sluice may warm dramatically. Meltwater running into the snowpack like this on some of the first warm days of the season has been known to do strange things. With this wet slab idea lurking in the background combined with the potential for icefall today, Low avalanche danger today still demands safe travel techniques and identifying hazards on the mountain.
- 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 7:55 a.m., Tuesday, February 21, 2017. A new advisory will be issued tomorrow.
Helon Hoffer, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856