Avalanche Advisory for Wednesday, February 7, 2018

Huntington Ravine will reach CONSIDERABLE and MODERATE avalanche danger. Central, Pinnacle, and Odell Gullies will reach Considerable avalanche danger. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential. All other forecast areas will reach Moderate avalanche danger. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully to identify features of concern.

Tuckerman Ravine will reach CONSIDERABLE and MODERATE avalanche danger. Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway will reach Considerable avalanche danger. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential. Right Gully, Lobster Claw, and Lower Snowfields will reach Moderate avalanche danger. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully to identify features of concern. The Little Headwall is the exception with Low avalanche danger. 

AVALANCHE PROBLEM: New wind slab that will form on today’s snowfall and moderate wind is our primary avalanche problem. This layer will be softer than our typical slabs formed on W and NW winds, but we do expect that the southerly wind today will make our new snow layer fairly cohesive. This means that you will be likely to trigger an avalanche in our steep terrain if you’re out late in the day. Dry loose sluffs will also be a concern late today and will contribute to slab development in our lower start zones. A secondary avalanche problem is the older and firmer wind slab formed early this week. This layer which seems of most concern in areas like the Sluice in Tuckerman and Central Gully in Huntington will be more difficult though still possible for a human to trigger.

WEATHER: It seems our wintry weather this week has been ramping up to today’s storm, which is forecast to bring 10-15” of snow to the mountain. Around 2 inches of new snow fell yesterday on westerly summit wind in the 40-50 mph range, as temperatures hovered around 0F. We currently have overcast skies and moderate wind out of the SW as the low pressure system approaches. Snowfall is forecast to begin in the next few hours and peak this afternoon, coming on southerly wind around 40 mph on the summit. Wind will shift through W to NW by late tonight as snowfall tapers. Summit temperatures should rise to the lower teens through today before dropping to around 0F again by tomorrow.

SNOWPACK: The fast moving and heavy hitting snow storm approaching the area will provide quickly changing avalanche conditions today and into tomorrow. This morning, our avalanche problem is rooted in the relatively smooth and firm wind slabs formed following the Sunday-Monday storm. The significant new snow inbound should fall on light to moderate southerly wind in the ravines, building soft storm or wind slabs by dark today that will likely be touchy to a human trigger in steep terrain. You will be less likely to trigger an avalanche in the currently existing slabs, but there will be potential for an avalanche in the new snow to step down into deeper layers. Late tonight and into tomorrow the wind shift and increase will transport significant amounts of snow and build large wind slabs that could ultimately result in natural avalanches. As mentioned above, avalanche danger will increase through this forecast period, particularly as wind shifts and increases after dark today.

 

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 or Harvard Cabin.
• Posted 8:15 a.m., Tuesday, February 6, 2018. A new advisory will be issued tomorrow.

Ryan Matz, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2018-02-07