Huntington Ravine has MODERATE and LOW avalanche danger. Central, Pinnacle, Odell, South, and Escape Hatch have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully, identify features of concern. North, Damnation, and Yale gullies have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.
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. Evaluate snow and terrain carefully, identify features of concern. Lobster Claw, Right Gully, Lower Snowfields, and the Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.
AVALANCHE PROBLEM: Wind Slabs formed through last week will be slow to stabilize with the cold air that currently dominates our area. The smooth slabs of most concern are fairly firm and can generally be found below the wind textured upper start zones of much of our terrain. Varying in thickness, such slabs are easiest for humans to trigger in thin areas where body weight can more easily impact an underlying weak layer. Remember that it’s difficult at best to visually estimate slab thickness. Though stubborn to a human trigger, a fracture in these hard slabs can propagate a great distance. This characteristic combines with chilling conditions to elevate the consequence of awakening our avalanche problem. As a secondary concern, keep softer slabs that will be significantly more isolated but of greater sensitivity to a trigger on your radar.
WEATHER: We’re ringing in the New Year but our weather is remaining largely the same. 60-70 mph wind and a high temperature of -13F on the summit made yesterday feel the most frigid of recent days despite inviting blue skies. Today NW winds will slightly reduce in speed to around 50 mph and the mercury will remain in the teens below zero with mostly sunny skies. Tuesday morning looks to be slightly more pleasant, with wind slackening a bit and air temperatures creeping another 10 degrees higher. Wind is forecast to elevate as is sky cover by the end of the tomorrow. Don’t expect to see measurable precipitation until later in the week when a low pressure system could impact our region, bringing snowfall and generally less arctic conditions.
SNOWPACK: You’ll find a mixed bag of surface conditions with large smooth slabs remaining if you venture into our terrain today. Motivated and savvy travelers could lessen exposure to today’s primary avalanche problem by sticking to heavily textured snow and exposed old crust. Our concern for facet growth in the upper snowpack will elevate the longer this very cold air remains in place. Snow pits should yield interesting results anywhere above tree line, with varying density wind slabs existing above and below the December 23rd crust. A variety of wind speeds and direction as well as natural avalanches since our last significant snowfall on Christmas have made for significant spatial variability in our upper snowpack. Do dig pits, but remember that their results will not tell the whole story for a particular slope.
• 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 7:30 a.m., Monday, January 1, 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