Avalanche Advisory for Thursday, March 8, 2018

Huntington Ravine has CONSIDERABLE avalanche danger. All forecast areas have Considerable avalanche danger. Dangerous avalanche conditions exist.

 Tuckerman Ravine has HIGH and CONSIDERABLE avalanche danger. The Lip and Center Bowl have High avalanche danger. Very dangerous avalanche conditions exist in those forecast areas as well as on the floor of the Ravine. Travel there is not recommended. All other forecast areas have Considerable avalanche danger. Dangerous avalanche conditions exist. The Little Headwall has Low avalanche danger with pockets of unstable snow, open water and holes in the snowpack.

AVALANCHE PROBLEM: New snow overnight plus a 50 mph ENE wind, which is more than capable of blowing new snow into wind slabs, are reason enough to avoid avalanche terrain today. Add 3-7” more snow and a shifting wind  today that will continue to blow snow into our larger avalanche paths and you probably have all the red flags you need to avoid trouble. Wind slab will continue to build today even as wind diminishes and will stress the weak snow below. Though the snowfall totals and wind direction so far don’t indicate particularly large avalanches happening in most places, small and medium sized natural avalanches are likely in many areas and are likely to entrain enough snow to carry and/or bury you. Loose dry avalanches are likely in many locations in Huntington Ravine, especially in northern gullies, Central and Pinnacle. These will be dangerous where they gain a head of steam. Sensitive wind slabs will likely be the primary avalanche problem in other forecast areas.

WEATHER: The nor’easter that is bringing mayhem to the Maine and New Hampshire coast is dousing us with a generous amount of snow water equivalent, with 7.5” of 10% density snow recorded at Hermit Lake at 6:30 a.m. Despite our distance from the coast and the center of the storm, the range continues to wring out snow from this system with light but steady snow continuing this morning. Later today, the center of the low pressure will move back on shore to our north and continue to draw moist air from the ocean through the day and bring continued snow fall before tapering to snow showers tonight. As the low retrogrades, wind will shift with it, continuing to shift from where it began from the east when snow began yesterday, through the ENE where it sits now, ultimately reaching a northwesterly direction by mid-afternoon. This northwesterly wind will be atypically light at 20-35 mph and so won’t dump the massive amounts of snow into the Ravines as these storms usually do, but the wind slabs that formed overnight will continue to be loaded by these winds just the same. Anticipate summit fog and snow to reduce visibility. Summit temperatures will be in the teen’s Fahrenheit.

SNOWPACK: As you have probably already concluded, our upper snowpack is showing many signs of poor stability. The icy refrozen snow that has dominated the surface also locked up deeper layers and has reduced our instability to the new snow from the past 24 hours and possibly a few remaining wind slabs that developed Sunday night and Monday. This storm started out fairly warm but the icy crust has proven resistant to bonding with new snow. There are a lot of variables at play at the interface with the new snow as well as in the new snow layers as wind shifts in speed and direction. You shouldn’t need to dig a pit to find unstable results today but hand shears, small test slopes along with snow and weather history are screaming warning signs pretty loudly.

The John Sherburne Ski Trail will likely see some action today. Snow earlier in the week freshened things up and covered most of the ice and a few rocks. Today’s snow fall will improve conditions further. Enjoy.

• 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 7:45 a.m., Thursday, March 8, 2018. 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