Avalanche Advisory for Wednesday, December 27, 2017

This advisory expires at Midnight.

Huntington Ravine has MODERATE avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible in all forecast areas. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully.

 Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. Sluice, Lip, Center Bowl, and Chute have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential. Lobster Claw, Right Gully, Left Gully and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Lower Snowfields and Little Headwall in Tuckerman have Low avalanche danger due to lack of a developed snowpack. Watch for unstable snow on isolated terrain features such as Dead End and Duchess above the Lower Snowfields.

AVALANCHE PROBLEM: Wind slabs exist through the terrain today following 11” of new snow in the past 48 hours. Sustained 60 mph westerly wind continued to load new snow into our avalanche start zones yesterday and will likely continue to do so today as they are now. Expect a mix of densities in these slabs from finger hard and stubborn to four finger and more sensitive to triggering. Considerable rated areas have a history of prolonged wind loading due to available snow in a W or NW wind so remain elevated today. Natural avalanches are a little more unlikely than possible but careful assessment and snowpack evaluation would be required to confirm. Our slopes continue to grow in area, creating the opportunity for larger avalanches. If you plan to brave the cold today to climb or ride in the Ravines, bring your A game.

WEATHER: The cold temperatures that are making headlines will make for challenging conditions on the mountain today. It is currently -23F on the summit with winds from the west in the low 70 mph range. Temperatures will warm slightly as wind diminish a bit today before plummeting again tonight as wind from the NW increase to near 100 mph. That ugly sweater that was too much for Christmas may be just right today.

SNOWPACK: The summit recorded 1.5” in the past 24 hours. The new snow added to the wind loading that has occurred in the past 48 hours following 9” that fell on the 25th. Limited visibility denied us a view of the upper start zones in Huntington and the bowl in Tuckerman but did allow some other avalanche observations. As expected, the ice crust encasing the 9” of snow that fell on the 22nd/23rd broke down and contributed that snow to the most recent avalanche cycle. This allowed Hillman’s Highway to avalanche around the corner, and Central, Odell’s and South to push pretty far towards the floor. It seems likely that other forecast areas avalanched as well but limited visibility has made closer observations unsafe.

The Lion Head Winter Route is open and the preferred route to the summit from the east side. Remember that natural or human-triggered avalanches can run out onto the floor of Tuckerman Ravine. Keep a safe distance if hiking up to have a look around.

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 8:05 a.m., Wednesday, December 27, 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

2017-12-27