Avalanche Advisory for Saturday, December 16, 2017

Huntington Ravine has Moderate and Low avalanche danger today. Central, Pinnacle, and Odell have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. North, Damnation, Yale, South, and Escape Hatch have Low avalanche danger. Natural and human-triggered avalanches are unlikely. Evaluate snow and terrain carefully.

Tuckerman Ravine has Moderate and Low avalanche danger. Sluice, Lip, Center Bowl, Chute, Left, and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Lobster Claw, Right Gully, the Lower Snowfields and Little Headwall have Low avalanche danger. Natural and human-triggered avalanches are unlikely. Evaluate snow and terrain carefully.

 AVALANCHE PROBLEM: Wind Slab will be our primary avalanche problem. This wind slab will be hard in nature and stubborn to a human trigger in many areas due to strong wind earlier this week. Watch for pockets of less firm and more reactive wind slab. Early season hazards still exist despite significant improvements in snow coverage over the past week. Exposed rocks and similar features could drastically elevate the consequence of being caught and carried in an avalanche.

 WEATHER: Yesterday was a day of cold temperatures and slackening wind, with only a bit of snow remaining for transport. Temperatures today will max out around 5F on the summit, with NW wind not exceeding 30 mph until this evening. Summit clouds are beginning to roll in and should remain through the day. We might see light snow showers this morning totaling 1 inch of accumulation. If you have good visibility early in the day, be aware that it might diminish significantly. Tomorrow looks quite similar to today, with less cloud cover. We may see light snow showers tomorrow night.

SNOWPACK: The past week has dramatically changed conditions, bringing significant snow and plenty of wind to move it around. Many of our avalanche paths have transitioned from a mess of ice and rock to full snow coverage. Wind approaching 100 mph earlier in the week has left firm and stubborn wind slab in most of these areas. This slab, and pockets of softer snow, lie above a varied surface of snow, ice, rock, and vegetation. If you’re digging into the snow today, remember that the variable nature of our snowpack will limit your ability generalize observations across the terrain. One pit might reveal new wind slab on bushes, while another might show the same slab on a smooth bed surface. As mentioned above, remember that many of our avalanche paths are just barely developed, and rocky consequences of a fall or avalanche capture are present in many locations. It’s still early season snow coverage.

The summer Lion Head Trail is the safer route to the summit than trails through Tuckerman and Huntington. The Lion Head Winter Route will open when snow fills in avalanche paths on the summer trail and fills in the winter route enough to cover rocks, mud and bushes. The John Sherburne Ski Trail has improved but there are still rocks and wind scoured bare areas. High wind has drifted dense snow in areas with generally challenging ski conditions prevailing.

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This bulletin 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 8:10 a.m., Friday, December 15, 2017. A new Advisory will be issued tomorrow.

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

2017-12-16