Avalanche Advisory for Saturday, December 23, 2017

Huntington and Tuckerman Ravine have CONSIDERABLE avalanche danger. All forecast areas have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Dangerous avalanche conditions exist. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential. Lower Snowfields and Little Headwall in Tuckerman have Low avalanche danger due to lack of a developed snowpack. Natural and human triggered avalanches are unlikely there. Watch for unstable snow on isolated terrain features such as Dead End and Duchess above the Lower Snowfields.

AVALANCHE PROBLEM: New snow yesterday created some wind slabs throughout the terrain. These slabs were built from low density snow on light to moderate winds and will remain touchy this morning. Furthermore, this snow comes with a lump of coal in your stocking. Warming temperatures, sleet and possibly a bit of rain will begin to load the new snow and wind slabs making them even more sensitive to a human-trigger and increasing the likelihood of natural avalanches. There are enough areas of softer snow from earlier in the week so it’s possible that an avalanche could entrain more snow than just yesterday’s snowfall. If you survive the freezing rain glazed roads to get to the mountain, you’ll have your hands full staying safe due to this mix of avalanche problems!

WEATHER: Snow will continue this morning before warm air overriding cold air at ground level brings sleet, then freezing rain to all elevations.  We may even see a greater variety in precipitation types, including plain old rain, as today’s weather brings nearly 0.5” water. Wind should remain moderate out of the S to SW through daylight hours. As precipitation winds down tonight, expect wind to shift to W then NW and increase to around 60 mph. This wind is forecast to continue through tomorrow, when we will also see a break in precipitation, partial cloud cover, and temperatures back down into the teens.

SNOWPACK: In the past 24 hours, the snowplots at 3800’ recorded around 15cm of 5.5% density snow with 8” recorded on the summit. Steady light to moderate snow (S-1 to S1) fell through yesterday starting at around 9am. The low density snow provided lots of good skiing on lower angled areas low in Left and Hillman’s and in Huntington. All parties wisely avoided the steeper, and more wind loaded upper start zones where loading was happening and some instabilities lingered from previous snow this week. As is often the case with light snow in steep terrain, dry loose avalanches, a.k.a. sluffing, occurred and was reported to be sizeable in Yale Gully in the afternoon. This recent avalanche activity highlights the potential danger today.

The Lion Head Winter Route is open and the preferred route to the summit from the east side. Daylight hours are short today…don’t forget to adjust your turn around time and bring your headlamp!

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 the Harvard Cabin.
• Posted 8:00 a.m., Saturday, December 23, 2017. 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

2017-12-23