Avalanche Advisory for Tuesday, January 23, 2018

Huntington Ravine has LOW avalanche danger. Watch for unstable snow on isolated terrain features.

 Tuckerman Ravine has MODERATE and LOW avalanche danger. The Lip has Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern. All other forecast areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.  The Little Headwall is mostly open water or frozen waterfall ice and is not rated.

Due to the open waterfall hole and a 20’ high avalanche 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 Notch. Other routes to the summit from the east side are more significant mountaineering challenges.

 AVALANCHE PROBLEM: The relatively small wind slabs built since late last week will become wet slabs as significant rainfall occurs today. Remember that triggering a small avalanche in consequential terrain can still have dire consequences. That said, natural and human triggered avalanches are unlikely today. The exception to these small slabs is “hang fire” in the area of the large avalanche crown in the Lip. Your primary concern in this location should be moisture and warm temperatures today that will decrease stability in the unsupported snow above the crown, which is currently a vertical wall of snow up to 20’ in height. Cautious travelers will avoid terrain under the Lip today for the high consequence of a large though unlikely avalanche from above this crown line.

 WEATHER: Up to 1” of new snow fell in our terrain overnight before warmer temperatures brought a change to wetter precipitation early this morning. It’s already above freezing at both Hermit Lake and the Summit. Summit temperature is forecast to hit the mid-30’s F today and not drop below freezing until after dark. By tonight rainfall will likely total approximately 1”. Moderate SW wind will shift W and increase late tonight as precipitation shifts back to snow. 2-4” of new snow is expected late tonight and early tomorrow morning and will taper off with decreasing cloud cover forecast for tomorrow as temperatures remain below freezing.

SNOWPACK: Small snowfall totals and the scouring and drifting effect of wind over the past week has left us with isolated pockets of wind slab over an exposed or thinly veiled crust. This crust formed over a week ago and is thick and very firm. The slide for life nature of a fall on this firm surface will decrease through the day as rain and above freezing temperatures soften surface snow, though a long sliding fall will likely remain possible. The unique hazard of concern today is an unlikely though potentially large avalanche from unsupported snow above the crown line of the massive wet snow avalanche out of the Lip that occurred last week. Rain and above freezing temperatures will weaken the previously frozen snow and a large avalanche could occur in this location. Spending time in the fall line of the Lip is not advisable for this reason.

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 8:15 a.m., Tuesday, January 23, 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

2018-1-23