Avalanche Advisory for Monday, March 6, 2017

This advisory expires at Midnight.

Huntington Ravine has LOW avalanche danger. All forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

Tuckerman Ravine has MODERATE and LOW avalanche danger. The Lip has Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. All other forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely. The Little Headwall is not forecast due to lack of snow.

AVALANCHE PROBLEM: Sunshine and warming temperatures will decrease the stability of existing wind slabs. These slabs are limited in distribution through our forecast areas with the largest of them in the Lip in Tuckerman, and to a lesser extent, low in Central Gully beneath the ice bulge in Huntington. These wind slabs were stubborn yesterday but are medium to large sized and potentially dangerous in the Lip and Center Bowl area. Smaller pockets of wind slab will weaken sooner and could pose a problem in steep terrain in other low rated forecast areas. Be wary of any of these wind slabs on east and south facing aspects today and do some stability tests or hand shears before committing to the slope. Old refrozen gray surfaces will present more stable travel options, though carry a greater risk of long sliding falls, especially on shady aspects. The snowpack is starting out quite cold so the timing of warming and associated softening of the snow is uncertain.

WEATHER: Calm winds are allowing an inversion this morning. Temperatures at 6:45a.m. are -2.5F at Pinkham Notch, 18F at 4,000’ on the Auto Road and 9F at the summit. Current winds of 25mph from the north are forecast to shift to the west and stay in the 20-35mph range but could be even lower. Low wind speeds and temperatures near freezing with sun, at least in the morning, may work to soften surface snow. High thin clouds, which may appear this afternoon as a warm front approaches, can increase this effect due to reflection of long wave radiation.

SNOWPACK: Strong northwest winds continued to transport snow through the morning hours yesterday. During that time, Ryan and I visited the crown face low in the Lip and our tracks and stability pit filled quickly with snow. The new wind slab was a meter thick in our location and the slab in many areas across the Lip forecast area is likely to be up to that thickness over the hard icy refrozen snowpack. Though we won’t see enough warming today to have significant wet slab concerns, the heat could certainly weaken the wind slabs, especially at the edges where they are thinner. Remember that wind slabs are easier to trigger in thinner spots, especially less than a meter thick. Yesterday’s crown profile indicated that the failure layer was 50cm down with another interface about 90 cm down both failing in the lower moderate (CT11 and 15) on a minor snow density change. Low quality shears (Q2) and a rugged pencil hard surface made the slab stubborn but anticipate growing sensitivity to human-triggers as the day wears on and warms the slab.

The Mount Washington Backcountry Ski Festival will be happening this coming weekend, March 10-11. A portion of the proceeds will benefit go to Friends of Tuckerman Ravine to help support our mission. Thanks again to Friends of Tuckerman Ravine, Allspeed, Black Diamond Equipment, Black Point Surf Shop, Julbo, Liberty Skis, Mammut, Ski the East, and Tuckerman Brewing for their generosity and support at last Thursday’s event in Portland!

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 Harvard Cabin.
  • Posted  7:35 a.m., Monday, March 6, 2017. A new advisory will be issued tomorrow.

Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2017-03-06