Avalanche Advisory for Tuesday, January 9, 2018

Huntington Ravine has Moderate avalanche danger. Heightened avalanche conditions exist and will continue to develop on specific terrain features. Evaluate snow and terrain carefully to identify features of concern.

 Tuckerman Ravine has Considerable and Moderate avalanche danger. Sluice, Lip, Center Bowl, and Chute will reach Considerable avalanche danger. Careful snowpack evaluation and cautious route finding are essential. Lobster Claw, Right, Left, and Hillman’s Highway have Moderate avalanche danger. Heightened avalanche conditions exist and will continue to develop on specific terrain features. Evaluate snow and terrain carefully to identify features of concern. Lower Snowfields and Little Headwall are the exceptions with a Low rating. Watch for unstable snow on isolated terrain features.

 AVALANCHE PROBLEM: Continued snow showers and wind loading today will continue development of our fresh wind slabs. A lack of visibility this morning following yesterday’s new snow and wind limits our ability to precisely determine size and distribution of these slabs. They will continue to develop today as slab building wind speeds continue and shift NW. We expect human triggered avalanches of small to medium size to be likely today in areas with greatest loading. With visibility possible this afternoon, your field observations of size and distribution for new wind slabs are crucial to determining how and where to minimize your exposure to today’s avalanche problem.

WEATHER: Consistent west wind of 60-70 mph on the summit has been transporting the 2-3” of new snow over the past 24 hours. Snowfall continues this morning and should taper through the day, giving us another 1-2” while wind shifts NW and increases slightly by the end of the day. A partial clearing of cloud cover is forecast for this afternoon. Temperature approached 20F at the summit and exceeded that at Hermit Lake yesterday. We should see slightly colder temperatures today that will drop this afternoon through tonight to just above 0F. Tomorrow temperatures will rise to around the freezing point in the ravines, with partial cloud cover and no measurable precipitation.

SNOWPACK: The new wind slabs that have developed over the past 24 hours, and continue to develop now, lie on firm and more stable slabs formed late last week. Uncertainty is the defining characteristic of today’s avalanche advisory, with a lack of visibility preventing us from determining size and distribution of slabs built since yesterday morning. Snow and NW wind this morning will continue this slab development, and we’re hopeful that increased visibility later today will bring more clarity to our current avalanche problem. We do know that recent and current wind speeds are ideal for turning the handful of inches of new snow into much thicker slabs that would be sensitive to a human trigger. If you have visibility of our avalanche paths today, make thorough observations to determine where and how large these new wind slabs are.

You will see changes to the advisory in the coming weeks and months as we try to find more effective ways to present the avalanche and mountain safety message in an efficient and helpful way. Today’s danger rating section purposely lacks likelihood of avalanche information which you will find in the problem section or in the North American Public Avalanche danger scale posted on kiosks or at the link on this page below the map.

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 8:00 a.m., Tuesday, January 9, 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

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