Avalanche Advisory for Friday, March 13, 2015

This advisory expires at Midnight.

Tuckerman has 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.  The Little Headwall has Low avalanche danger.

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 concern today.  High winds through the day on Thursday averaged around 70-80 mph (112-128kph). This loaded approximately 3.5-4” (10cm) of new snow down into the Ravines.  This resulted in some natural avalanche activity in Tuckerman followed by reloading. The greatest wind slab problem exists from the Sluice, through the Lip, towards the Center Bowl. These areas are on the upper end of the Moderate definition based their potential to react to a human trigger. In Huntington Ravine most new snow was scoured out, with a few isolated pockets to watch out for.  Keep your eyes open down low on approaches and in the protected trees.

WEATHER: The day is starting out cold, clear and windy.  A low pressure will begin to move in today bringing in some dropping clouds, warming temperatures and decreasing winds.  Expect wind velocities to fall from about 70 to 40mph and shift from the NW to the W as the mercury climbs to 10F (-12C). Tonight precipitation will slowly begin and last through the weekend.

SNOWPACK: Yesterday the Ravines were veiled in a silky shroud of drifting snow.  The Ravine’s muted horizon line was barely discernable with +/-3 to 4” of new snow loading in, creating poor visibility.  This generated new slab development and some natural activity, which we’ll take a closer look at today.  Crown lines have been reloaded and are only partially visible across the Lip area.  I would have the greatest concern in the Lip and Sluice today as they currently retain the most new snow, likely to be a mix of pencil (P) and 1 finger (1F)  hard slabs.  They also are loaded over a potential weak layer and crust that developed earlier in the week. We will confirm this today and look for any early faceting that occurred around this old surface, created by warm wet snow and negative temperatures.  As you move towards the S side of Tuckerman, down low in the Chute and Left Gully, you will probably find a harder slab that often occurs with high NW winds.  Higher in the Chute you will find soft slab that should be more reactive to a human trigger. This is also likely near the upper start zones of Left gully, but to a lesser degree.  Left Gully and Hillman’s Highway are both close to being Low danger, but have just enough concern to keep them at Moderate today.  In Huntington, scouring winds scalped a number of gullies down to old surfaces more than in Tuckerman, so a Low danger rating is most appropriate.  However some isolated pockets do exist so stay aware and evaluate snow throughout the day.

Tonight precipitation will move in and could, could, start as rain or freezing rain in the Ravines before transitioning to snow through Saturday and into Sunday.  This event will keep avalanche danger elevated and you will likely see some Considerable danger ratings on Saturday and more so on Sunday.

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 13, 2015. A new advisory will be issued tomorrow.

Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2713

2015-03-13