Avalanche Advisory for Saturday, December 13, 2014

This advisory expires tonight at 12:00 midnight.

Tuckerman and Huntington Ravines have Considerable avalanche danger. Dangerous avalanche conditions exist. Natural avalanches are possible and human triggered avalanches are likely.  Careful snowpack evaluation, cautious route-finding and conservative decision-making are essential.

This is the initial Avalanche Advisory for the 2014-2015 season using the North American Public Avalanche Danger Scale (a.k.a. the “5-scale system.”) Bear in mind that the existing conditions and snow coverage are in a state of transition. We recognize that Considerable is a strong rating for the paths that are just beginning to fill in with snow, but in others where the bed surfaces are much more developed we feel this rating most accurately describes the potential hazard today. Naturally triggered avalanches are a possibility. You will need to be able to carefully assess the terrain as well as the snowpack in order to minimize your exposure to the hazard.

AVALANCHE PROBLEM: Wind slabs are the primary avalanche problem for today due to recent snow being redistributed around the mountain. Slabs will form on a variety of early season surfaces, including water ice and ice crusts from the recent thaw.

WEATHER: The weather on Mt. Washington has been substantially different than down in the valley over the last few days. Tuesday night we received a heavy dose of wet snow, which was followed up by some rain and mixed precipitation. Following this the temperature lowered and we began to receive snow. Approximately 5″ (12.5cm) were measured at the summit since Thursday morning. Today’s forecast calls for an additional 1-3″, bringing to total amount sitting above treeline and available for transport to somewhere around 6-8″ with an average density of about 9%. Wind today will be from the NW and gusting into the mid-60mph range (95-100kph), which should be sufficient for loading to take place.

SNOWPACK: The warm spell that followed the heavy snow is setting the stage for avalanche activity. It left behind an ice crust that can act as a slippery bed surface for new wind slab to build on. When the winds shifted from the E to the NW on Thursday, they started out rather light. Expect a layer of light density snow between the crust and the denser slabs at the surface. Newly developing slabs with these conditions may feel soft and and buttery smooth underfoot, but even the small ones can be dangerous if they take you off your feet and into the rocky terrain below.

As mentioned earlier, the snowpack is in a transitional state. We are primarily concerned about the locations where bed surfaces have been developing faster. As is typical, these areas include the Lip, Center Bowl, Chute, and Left Gully in Tuckerman. In Huntington, you’ll find that Central has the largest snow surface but potential bed surfaces exist in multiple gullies. The exit snowfields in Damnation, Yale, Central, and Odell strike me as places where unstable slabs might be found. Also don’t overlook the smaller snowfields down lower in the ravine, such as on the approaches to climbs like Yale, Central, and Pinnacle.

There are some forecast areas that are not likely to be truly at Considerable danger. After the clouds clear from the mountain and we can make more accurate assessments, we may bring these areas down to “Not Posted” due to a lack of snow. Until then, we want you to recognize that hazards may exist even in smaller terrain features. Lobster Claw, Right Gully, the Lower Snowfields, and Little Headwall in Tuckerman fit this description, while in Huntington, the Escape Hatch is the leading contender for not reaching Considerable danger today.

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. December 13, 2014. A new advisory will be issued tomorrow.

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

2014-12-13