Avalanche Advisory for Tuesday, January 10, 2017

This advisory expires at midnight.

All forecast areas of Huntington and Tuckerman Ravine have LOW avalanche danger. Natural avalanches and human-triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features. Lower Snowfields and Little Headwall are not rated due to a lack of snow but look for overhead hazard in Lower Snowfields which remains mostly tree covered except beneath Duchess.

Incoming snow this evening will increase avalanche danger. Once snow begins to fall, expect increasing avalanche danger. If we receive the upper forecasted amount, we will likely exceed the Low danger rating tonight, passing through Moderate and into Considerable by tomorrow morning. Traveling in terrain today once the snow begins will require constant reevaluation of your plan.

AVALANCHE PROBLEM: Travel in avalanche terrain today will require the navigation of Wind Slab. This formed over the past 48 hours from steady west winds. While scouring may have taken place in areas, expect to find widespread newly formed wind slab in lee areas of most terrain features. Pockets of softer snow may exist and will be easier to trigger than the firmer wind slab. Snow will arrive later today along with increasing winds, creating new and larger wind slabs that will increase the avalanche danger overnight.

WEATHER: Over the past two days, a trace of new snow has fallen in the Cutler River Drainage. West winds averaged in the low 40mph range with gusts into the high 70s. Temperatures remained cold, with a current maximum of 7F on the Summit. Today, a warm front will sweep through, bringing clouds as the day progresses. It looks like snow will start mid-afternoon, picking up in intensity through the night. By daybreak tomorrow, we could see up to 8” at Hermit Lake. Temperatures will warm and lower elevations will see rain, but it looks like the higher summits will stay cold enough to remain snow.

SNOWPACK: Winds over the past 48 hours have blown loose snow that remained in our fetch into the ravines. Numerous ski tracks laid down on Sunday are now completely covered with new snow. Digging into the snow in many areas will reveal several crusts. While the recent cold temperatures are driving the faceting process, we have only once seen these layers reactive, and that was to a significant trigger. New snow will be arriving around dusk. With temperatures warming, expect this snow to be heavier than the current surface. Winds will be increasing and shifting from the south to the west, all contributing to the development of an upside-down snow structure. Thinking about red flags that exist, of note is the recent avalanche activity in the Center Bowl. This appears to have been triggered by the hanging dagger of ice that always forms in the Headwall. Sunday night, this massive piece of ice fell and triggered a slab that also appears to have stepped down a layer, but not yet to the basal ice crust. If traveling in terrain past dark or planning a trip tomorrow, keep this activity in mind. Expect the snow overnight to increase avalanche danger. With the presence of layers of facets and graupel in the snowpack that have been shown to be reactive to a large trigger, I would be wary of what up to 8” of heavy windblown snow will do overnight and through the day tomorrow. The snow will serve as the load without the need for a huge dagger of ice.

The Lion Head Winter Route is open and the most direct route to the summit from the east side of the mountain. Please be on the lookout for machine traffic on the Sherburne as we remove construction debris over the coming week.

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 8:15 a.m., Tueday, January 10, 2017. A new advisory will be issued tomorrow.

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

2017-01-10