Avalanche Advisory for Wednesday March 05, 2014

This advisory expires at 12:00 midnight

Tuckerman Ravine has Moderate and Low avalanche danger. The Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully. All other forecast areas have Low avalanche danger. Natural and human triggered avalanches are unlikely in these areas.

Huntington Ravine has Moderate and Low avalanche danger. Central Gully has Moderate danger. Natural avalanches are unlikely and human triggered avalanches are possible. All other forecast areas have Low avalanche danger. Natural and human triggered avalanches are unlikely in these areas.

AVALANCHE PROBLEMS: Wind Slabs are the primary avalanche problem today. The most widespread wind slab problems can be found in the Sluice through the Chute of Tuckerman. They are interspersed with the secondary problem, Persistent Slabs.  These are in the form of older pencil hard wind slabs in varying stages of early faceting which has created variability in areas such as Left Gully, Hillman’s, and Central Gully in Huntington.

WEATHER: The summit picked up 0.7” (1.75cm) in the last 24 hours and is currently seeing light snowfall.  Snow showers are expected to deliver up to an additional 2” (5cm) today.  If recent history is a guide to forecasted snow amounts, it’s unlikely we will see this much fall. Building winds will stay fairly modest moving from the current of about 20-25 (36kph) to 40 mph (64kph) later today.  High pressure sliding in will bring arctic air to the mountains again dropping the mercury to -15F (-26C) for the high peaks.  A warming trend into the weekend should offer more seasonable temperatures before moving back into sub-zero F conditions next week.

SNOWPACK: Recently snowpack discussions have revolved around the freezing rain (ZR) crust from 2 weeks ago.  Specifically, are there multiple new wind slabs sitting on top of this layer? Or have they been scoured back down close to the crust?  This issue is the primary driver of our spatial variability.  Additionally, this crust has been slowing changing, being cannibalized through the temperature/pressure gradient created recently from the arctic air.  This process, in addition to vapor transfer from areas further away from the crust, has created facets below and above the crust.  This in turn has weakened the ZR layer, contributing to the persistent slab problem.  As you travel this crust should be a reference point to look for in your snowpack evaluations.  Mainly, how deep in the snowpack is this crust?  In places where newer wind slabs are layered over the crust I would focus attention to how the upper slabs, closer to the surface, are bonded between hardness transitions first. Then focus on the facet development just above this breakable layer.  This priority will be dependent on depth of the crust and the degree of facet development.  As W and NW winds move new, light amounts of snow into the Ravines keep your eyes peeled for new soft slab in pockets.  Realize areas posted at “Low” may have isolated pockets of instability to watch out for this afternoon.  Pinnacle, Odell, and South gully in Huntington are prime locales to consider this situation.

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 the Harvard Cabin.Posted 8:35a.m. March 5, 2014. A new advisory will be issued tomorrow.

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

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