Avalanche Advisory for Friday, March 20, 2015

This advisory expires at midnight.

Tuckerman Ravine has Moderate and Low avalanche danger.  The Sluice, Lip, Center Bowl, Chute and the Lower Snowfields have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.  Heightened avalanche conditions on specific terrain features exist so evaluate snow conditions carefully to identify features of concern.  Lobster Claw, Right Gully, Left Gully, Hillmans Highway and the Little Headwall have Low avalanche danger. Natural and human-triggered avalanches are unlikely but watch for unstable snow on isolated terrain features.

Huntington Ravine has Low avalanche danger.  Natural and human triggered avalanches are unlikely except in isolated terrain.  These pockets of concern do exist is some locations.

AVALANCHE PROBLEM: Wind Slabs are the primary avalanche problem today. You will find firm and stubborn to trigger wind slabs scattered around our terrain with the greatest concentration of larger wind slabs in areas that are rated Moderate. The bull’s-eye for these wind slabs is in the Sluice, Lip and Center Bowl area where slopes have smoothed and grown much more continuous over the past week or so. Smaller, but still potentially unstable wind slabs, exist in some areas isolated areas within Low rated areas.  Assess these areas carefully from the relative safety of old hard surfaces. Consider the de-stabilizing contribution that some limited heat from the sun may have on south facing slopes, especially in Tuckerman where the recent wind slabs are more widespread.

WEATHER: The windy weather of the past several days is well understood by valley residents. Branches and downed trees on the surface of the snow and wide spread wind scouring of slopes and gullies in many places testify to the protracted period of high winds that we have experienced on the mountain up until mid-day yesterday. Finally, the wind has abated as fair weather visits us briefly today. Summit temperatures have risen from 0F (-18C) last night at midnight to 16F (-9C) this morning where they are expected to remain though the day until the next arctic cold front approaches tonight. Clouds will build overhead this afternoon with new snow (Trace – 2” or 5cm) falling tonight. Calm winds from the west at 10-25mph (15-40 km/h) with some higher gusts to 40 mph (65km/h) will provide a nice break from the recent wicked winds. More snow, with winds blowing at an ideal rate for loading our forecast area, will probably elevate our avalanche danger Saturday and Sunday.  In addition, expect wind velocities to rage over 100mph and the mercury to dive deeply below 0F on Saturday night.  Keep a close eye on the Mount Washington Observatory weather forecast for more updates and check back for the latest avalanche advisory each morning.

SNOWPACK: Field time yesterday confirmed the hammering that our slopes received. Heavily sculpted snow (sastrugi) is the dominate feature of surface snow in many areas and in most areas of Huntington Ravine. Elsewhere, in the lee of northwest winds and at lower elevations in Huntington, wind transported snow grains packed into finger to pencil hard, smooth slabs which yields to boots and ski edges. In many areas, the older exposed surface is icy, so without crampons you would be forced to be a slope stability tester by travelling on the smoother and slightly softer wind slabs. Today seems to be the nice weather window for the weekend and will likely be the only day of the weekend with good stability. Remember that Low ratings carry with it the full weight of the North American Public Danger Scale, including travel advice and avalanche size and distribution. Don’t be bashful about reminding people that Low avalanche danger doesn’t mean no avalanche danger. We still have a dynamic winter snowpack, despite today being the first day of spring, so bring your avalanche skills and rescue gear if you want to play on the mountain.

Please Remember:

  • 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 8:40 a.m. March 20, 2015. 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

2015-03-20