Avalanche Advisory for Wednesday, January 10, 2018

Huntington Ravine has MODERATE and LOW avalanche danger. Yale, Central and Pinnacle Gully have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully. All other forecast areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.

Tuckerman Ravine has MODERATE and LOW avalanche danger. All forecast areas have Moderate avalanche danger. Evaluate snow and terrain carefully today. The exceptions to this rating are Lower Snowfields and Little Headwall which have Low avalanche danger. Watch for unstable snow on isolated terrain features. The Little Headwall is skiable out of the bowl though open water in the stream above makes it challenging.

AVALANCHE PROBLEM: Wind slabs which developed in the past couple of days will be the primary avalanche hazard. Widespread, though variable in density, wind slab is the primary hazard due to the larger potential size of an avalanche. These slabs are largest across the Headwall from Sluice to Chute in Tuckerman Ravine and in Central Gully, around the Fan and beneath and in the mid-section of Yale. A new crown line high in Duchess points to the potential danger today. Also on the list of concerns are the snow pellets which fell mid-morning yesterday which pooled and formed a slab in places. These are probably very sensitive to a human trigger. These are more than likely only capable of generating a small avalanche but could be consequential above steep terrain or if they catch you by surprise. Graupel can create sizable slabs beneath steeper ice in Pinnacle, Odell and South as well. Move carefully in the terrain today to stay above both of these hazards and be wary of committing to larger slopes.

WEATHER: It’s a balmy 20 F at Hermit Lake this morning under clear skies. The temperature will continue to rise today, reaching the mid-20s F on the summit. Wind will shift NW to W and increase slightly to the 30-45 mph range which is not likely to transport any more snow into our terrain. Temperatures in our forecast area will likely rise close to the freezing mark though won’t likely contribute to any instabilities. The main concern stems from the 7” of snow which has fallen on loading speed winds in the past 3 days. Looking ahead, expect the dreaded January thaw to strike this week with an ugly ice crust creating slide for life on tap for the weekend.

SNOWPACK: New snow and the resulting wind slabs built over the past several days are mostly sitting above firm slabs. The exception to this would be across the Headwall and in some upper start zones where some softer but unreactive snow had blown in over last weekend. Though not likely to be the weak layer in an avalanche today, this snow could contribute to the volume of snow in an avalanche. Strong wind yesterday moved lots of snow but the wind speeds were not high enough to do a lot of scouring or pack the snow into strong and unreactive slabs like we can get in a prolonged blow. If you plan to take advantage if this nice weather window, bring a solid partner and assess the snow carefully before committing to the slope.

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 8:10 a.m., Wednesday, January 10, 2018. 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

2018-1-10