Avalanche Advisory for Sunday, April 8, 2018

Huntington Ravine has CONSIDERABLE, MODERATE, and LOW avalanche danger today. Central Gully has Considerable avalanche danger. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential. Yale, Pinnacle, Odell, South, and Escape Hatch have Moderate avalanche danger.  Evaluate snow and terrain carefully to identify features of concern. North and Damnation have Low avalanche danger. Watch for unstable snow on isolated terrain features.

Tuckerman Ravine has CONSIDERABLE, MODERATE, and LOW avalanche danger today. Sluice, Lip, and Center Bowl have Considerable avalanche danger. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential. Right Gully, Chute, Left Gully and the Lower Snowfields have Moderate avalanche danger.  Evaluate snow and terrain carefully to identify features of concern. Lobster Claw, Hillman’s Highway, and the Little Headwall have Low avalanche Danger. Watch for unstable snow on isolated terrain features.

AVALANCHE PROBLEM: The 6” of snow that arrived Friday night on increasing west wind formed wind slab in all forecast areas. This wind slab proved touchy to human triggers yesterday with skier-triggered avalanches in Lobster Claw, Chute, Hillman’s Highway and the Little Headwall. Slab depths were up to 14” thick and while nobody was buried, enough snow was entrained to carry at least five people downhill in the Hillman’s avalanche. Size and distribution of this avalanche problem is aspect driven. East facing slopes (Considerable rated areas) contain more widespread wind slab capable of producing large avalanches. North and south-facing slopes (Moderate and Low rated slopes) contain smaller areas of wind slab that could produce a small avalanche. In addition to the avalanche problem, the exposed icy crust will make long, sliding falls a hazard today, particularly this morning before things warm.

WEATHER: Friday night into Saturday morning, the Hermit Lake snow plot recorded 6” of new snow while the summit received just under 5”. This was followed by clearing skies through the day on Saturday with a high temperature on the summit of 12F and an average wind speed of 50mph from the west. Last night, winds calmed to a current 15mph from the NW. Today, wind will remain from the NW and stay calm for the morning before beginning a gradual increase through the afternoon, reaching the 50-70mph tonight. Temperatures will increase to the teens on the summit. High clouds will be intermittent this morning with low and mid-level clouds developing in the early afternoon. There is also a chance for up to 1” of snow in the afternoon.

SNOWPACK: Wind slab sits on top of the icy melt-freeze crust that formed over the past week. Formed primarily Friday night with lesser wind loading continuing into last night, this wind slab has not bonded well to the bed surface and is reactive to human triggers. The bed surface will be icy this morning and may soften in the afternoon due to solar gain. The wind slab will remain reactive through the day. Safe travel techniques like not skiing or climbing under other people and traveling one at a time across a slope are key to getting home at the end of the day. The incident in Hillman’s Highway yesterday highlights this when a skier triggered avalanche in the looker’s left fork caught and carried multiple people below who were skiing and climbing. Other people on a slope do not mean the slope is safe, rather, they are potential triggers out of your control.

Check our Instagram for photo updates, we’ll post more specific information if we get any visibility today! You don’t need an account, just follow the link on our website.

 Boston folks: Join us on Tuesday, April 10, from 7-10 pm at Arc’teryx Boston for a night of learning, socializing, and free gear! Free to attend, but space in limited, register at eventbrite.com.

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This advisory 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.
• Posted  8:40 a.m., Sunday, April 8, 2018. A new advisory will be issued tomorrow.

Helon Hoffer, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2858

2018-04-08