Avalanche Advisory for Thursday, January 11, 2018

Huntington Ravine has MODERATE and LOW avalanche danger. All forecast areas have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully. North, Damnation and Yale 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 Left Gully, Lower Snowfields and Little Headwall which have Low avalanche danger. Watch for unstable snow on isolated terrain features.

AVALANCHE PROBLEM: Warm temperatures penetrating existing wind slabs keep danger ratings elevated today. Wet slab and wet loose avalanches should be on your radar today. These avalanche types are notoriously hard to predict but human-triggered avalanches in our warming, softer slabs are possible in steep wind loaded terrain. Natural avalanches of this type seem unlikely but I would not hang around beneath larger slopes today. Low rated areas in Huntington harbor the potential for these problems; while an avalanche there would be small in size, the steepness of the terrain raises the stakes. Moderate rated areas in our terrain are also steep and contain thick enough soft wind slabs to generate an avalanche large enough to bury you. Evaluate snow and terrain carefully if you choose to go into the Ravines.

WEATHER: The summit temperature is currently 34F, Pinkham Notch 31F, with 43F at 4,000’. Light rain and drizzle began on the summit around 1am this morning as air temps pushed to the freezing mark. 3mm of rain was collected at Hermit Lake. Temperatures will continue to rise today as southwest flow brings a January thaw. Highs on the summit will reach 40F. Expect wids to shift SW late in the day from the current W and decrease slightly to the 50-70mph range. Fog will challenge visibility most of the day. Tonight rain will fall more heavily at all elevations with 1.8” of rain currently in the forecast. Expect elevated avalanche danger through the night and into tomorrow due to this rain.

SNOWPACK: Jeff and I took advantage of good visibility and moderate weather yesterday to make some field observations in Tuckerman Ravine. Signs of a widespread avalanche cycle were apparent still in Center Bowl, Chute and Left Gully though the Lip and Sluice areas had reloaded. The softer wind slab which developed primarily Monday and Tuesday was around 4F-1F and variable in thickness as well as density. Similar wind slabs appeared to be present in Central and other moderate rated gullies in Huntington. They proved to be unreactive with only a little graupel mixed into the softer areas of wind slab and no pooling observed in Right, Sluice, Chute or Left Gully. Lots of old pencil hard wind slabs were at the surface in more scoured locations. Snow temperatures 20cm down this morning have already reached -.5C at Hermit Lake.

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., Thursday, January 11, 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

2018-1-11