This advisory expires at 12:00 midnight.
Tuckerman and Huntington Ravines have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Careful snowpack and weather evaluation is essential today. The only exception to the Considerable rating is the Little Headwall in Tuckerman which has Low avalanche danger.
AVALANCHE PROBLEM: Our primary and secondary avalanche problems today are Wind Slab and Wet Slab. Which type of slab carries the most risk depends on temperature and precipitation type and rate. New snow this morning (1-3″) deposited by WSW winds will lead to the development of Wind Slabs. If incoming precipitation falls as rain, which is unlikely but possible, recent wind slab could change into our secondary avalanche problem – Wet Slab. A distant third problem is deeper, Persistent Slabs. Older, deeper wind slab layers could be activated by increased load and warm temperatures today. None of these hazards are expected to generate many natural avalanche releases but given the rapidly changeable nature of mountain weather, a wise traveler will pay close attention to type and rate of precipitation today in case rain shower activity is heavier than forecasted. And although 1-3″ of new snow isn’t much, history has shown this amount can turn into a problematic wind slab.
WEATHER: A mix of precipitation, reduced visibility and increasing winds are on tap for today. A warm temperature band mid-mountain this morning turned snow showers in Pinkham to light rain mid-mountain. Forecasts call for snow before noon with a slight chance of rain before turning to freezing rain in the afternoon. Wind from the WSW at an effective loading speed (45-60 mph, 72-97 kph) will increase a bit in the afternoon before shifting W this evening with the passage of a cold front. A more significant precipitation maker Saturday night has forecasters charged up.
SNOWPACK: Our snowpack is a mixed bag of Wind Slabs in the upper meter of snow. Some temperature crusts also exist, probably with some early faceted snow nearby. The location and depth of these layers varies widely depending your location but expect greater hazard to exist on the very steepest lee areas and slopes with the fewest anchors. The upper snowpack is dominated by hard, ergo strong, wind slabs so they will be stubborn in most locations. Fresh wind slabs, grown yesterday, were pockety and mostly built from highly decomposed snow crystals that packed pretty tightly. Highly textured, wind sculpted sastrugi was widespread. Sluice and Center Bowl had larger areas of more continuous and smooth wind slab and would be areas I would avoid entirely today. High winds in the past 36 hours pushed snow further down into our terrain like the Lower Snowfields and the big slope beneath Damnation and Yale. Though lower angle, these areas are large and continuous and could produce a larger avalanche. Air temperature has increased 36F (20C) degrees in the 24 hour period starting at 7 am so anticipate some weakening of the upper slabs. Ultimately this warming will encourage a breakdown of angular crystals and lead to more stability but we will pass through a period of relative instability to get there.
Spring is in the air this morning but it is not the type of spring day that encourages an outing into the alpine. If I were you, I’d continue to be patient for better weather that must be around the corner. After all, it is Spring. Right?
- 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 a.m. 3-28-2014. A new advisory will be issued tomorrow.
Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856