Avalanche Advisory for Wednesday, February 10, 2016

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Considerable and Moderate avalanche danger. The Sluice, Lip, Center Bowl, Chute, and Left Gully will have Considerable danger. Dangerous avalanche conditions exist. Natural avalanches are possible and human-triggered avalanches are likely. Right Gully and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Lobster Claw, Lower Snowfields, and Little Headwall remain not posted due to a lack of snow in these locations.

All forecast areas of Huntington Ravine will have Considerable avalanche danger. Dangerous avalanche conditions will exist. The only exception to this is the Escape Hatch, which will have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible in this location.

AVALANCHE PROBLEM: Today’s avalanche problem is predominantly the growth of new, relatively soft wind slab. Most areas in both ravines are starting the day in the Moderate range, but with the addition of more snow and increasing winds in the afternoon, expect avalanche danger to exceed Moderate before the end of the day. New slabs will likely be deceptively soft. Remember that we’ve only received a few inches of new snow in the last two days. If you find pockets of soft snow deeper than this in steep terrain, be aware that this is number one avalanche problem today. The overall size and destructive potential of avalanches you may see today might be smaller, but it doesn’t take a large avalanche to ruin your day.

WEATHER: About 5″ (12.5cm) of new snow has fallen on the summit of Mt. Washington in the last couple days. Don’t get too excited about shin-deep skiing though, down at Hermit Lake and at Pinkham it’s only been a few inches. And the snow is very light density (4-5%), so it’s not doing much to cover the nasty ice crust left from last week. Today there might be up to 2″ of new snowfall, which would also be low density and easily transported on the rather light winds we expect to have for much of the day. One very important piece of weather history is that while snow fell, winds were nearly calm. Overnight, winds rose up to 30+mph (48kph), causing some of the new snow to redistribute into favored lee areas of the ravines.

SNOWPACK: The increase in winds last night likely caused some slabs to grow in many locations. Currently, everything is an even shade of gray with a few flakes falling, so I don’t know exactly where or how big the wind slabs grew. I suspect they were able to develop in most of the forecast areas, with Central Gully, the Lip, and Center Bowl being the areas of greatest concern. Beneath new wind slab, you’ll find a layer of weak unconsolidated snow.  Due to light winds, the upper elevations of the gullies probably saw more wind loading than farther down low. In Huntington, I’d also caution you to be suspicious of the approaches to ice, where sluffing may have built deeper piles of slab on steep slopes. Approaching Pinnacle is a prime location for this type of issue. Later today and into the evening, when winds get another boost and more snow has fallen, I believe we will see avalanche hazard rise above where it’s been sitting all day. So if you are out late, pay close attention to the snow underfoot!

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. February 10, 2016. A new advisory will be issued tomorrow.

Jeff Lane, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-285

2016-02-10