Avalanche Advisory for Monday, March 19, 2018

Huntington Ravine has MODERATE and LOW avalanche danger. Central Gully has Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern. All other areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.

 Tuckerman Ravine has MODERATE and LOW avalanche danger. Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully to identify features of concern. All other areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.

 AVALANCHE PROBLEM: Wind slab remains our primary avalanche problem today. Generally firm and relatively stubborn to a human trigger, these recently formed surface layers are of most concern in Moderate rated areas where they are particularly large, potentially well-connected, and smooth on the surface. These surface slabs are layered over others formed in the past week, and while we’re not overly concerned with an avalanche initiating deep in the snowpack, it’s worth considering that an avalanche today could ultimately entrain a great deal of snow. It’s a low probability/ high consequence kind of day, with your likelihood of triggering an avalanche not exceeding “possible”. Travelling one at a time through and below avalanche terrain, from safe zone to safe zone, remains a wise and relevant practice on days like today.

 WEATHER: Today is forecast to be a near repeat of yesterday, as high pressure holds a cold air mass over our region. High temperatures on the summit should mimic the -3F recorded yesterday as wind remains NW in the 60-80 mph range until possibly diminishing a little tonight. The current summit fog should give way to clear skies. Tomorrow looks to be a more pleasant day, with temperatures 10 degrees warmer and NW wind decreasing through the day. Increasing high clouds are also forecast tomorrow but we shouldn’t see any precipitation.

SNOWPACK: Cold temperatures which slow stabilization and minimal wind transport in the past 24 hours mean that our snowpack remains much as it was yesterday. The multiple bouts of 100+ mph summit wind since last week’s series of Nor’easters has created largely firm snow conditions. These wind speeds create a great deal of spatial variability in our snowpack, with new slabs of great thickness in some areas while fairly thin in others. Character of these new layers varies accordingly, though we don’t expect sensitivity to a trigger to push beyond “stubborn” in these generally hard slabs. The exception would be small and isolated pockets of softer snow which may remain touchy. Yesterday was the first day of good visibility following our successive storms, and it revealed evidence of widespread mid-storm avalanche activity. Gullies that did not produce an avalanche, if any, were the exception rather than the rule. Of particular note are significant broken trees and avalanche debris just a few feet looker’s right of Connection Cache in Tuckerman Ravine. We don’t believe an avalanche has run to this area in recent years, and it’s an excellent reminder that a large avalanche can threaten flat terrain well below it.

The Harvard Cabin will be open all nights this week.

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 8:00 a.m., Monday, March 19, 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