Avalanche Advisory for Sunday, January 21, 2018

Huntington and Tuckerman Ravines have LOW avalanche danger. Natural and human-triggered avalanches are unlikely in all forecast areas.  Watch for unstable snow on isolated terrain features.  The Little Headwall is mostly open water or frozen waterfall ice.

Due to the open waterfall hole and 20’ crown line, the Tuckerman Ravine Trail is closed in the Ravine between Lunch Rocks and the Alpine Garden Trail. Please use the Winter Lion Head Route if going to the summit from Pinkham. Other routes to the summit from the east side are significant mountaineering challenges.

 AVALANCHE PROBLEM: Isolated pockets of wind slab exist in our terrain, though much of the snow surface is very hard and refrozen following the warm-up that occurred late last week. This very hard, icy snow will likely be your primary travel concern today for its potential to allow a long sliding fall. If you did trigger a small wind slab avalanche, it could easily knock you off your feet and cause such a fall. Realize that even those who are highly skilled in steep snow climbing with crampons and ice axe would have little chance of effectively self-arresting to stop this kind of slide. Additionally, melt out of rocks, trees, stream beds, and other hazards in the fall line of steep terrain make a traumatic outcome of a long sliding fall likely.

 WEATHER: It’s currently 13F on the summit and 22F at the Hermit Lake snow plot with a trace of new snow that has fallen early this morning. Yesterday was partially cloudy in the alpine with peak westerly wind near 100 mph. Temperatures pushed over 20F on the summit and just exceeded the freezing point at Hermit Lake. Today should be similar in temperature and cloud cover though slightly less windy, with current NW wind near 70 mph decreasing through the day. Despite the few flakes currently falling at Hermit Lake, we won’t see measurable snowfall. Tomorrow is forecast to be a few degrees warmer with wintry though possibly mixed precipitation beginning roughly in the middle of the day.

SNOWPACK: As you might already know, very hard refrozen snow dominates our terrain. Scattered pockets of wind slab do exist and should be respected, but avalanches are probably a secondary concern to long sliding falls today. The several inches of rain and prolonged warm temperatures that ultimately resulted in this hard surface “crust” of several inches to a foot or more in thickness also produced a massive wet snow avalanche out of the Lip. The crown line at the top of where this avalanche pulled out is up to 20 feet tall and vertical. Warmer temperatures forecast early this coming week could allow instabilities to develop in the unsupported snow above the vertical wall of this crown, creating potential to significantly increase overhead hazard in an area that has been stable over the past week. We don’t expect temperatures to warm to this degree today, but rather keep much or all of our snow a cold, hard surface that necessitates a high level of caution and skill in steep terrain to avoid a slide for life kind of fall.

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 Harvard Cabin.
• Posted 8:20 a.m., Sunday, January 21, 2018. 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

2018-1-21