Avalanche Advisory for Thursday 1-24-2013

Expires at Midnight 1-24-2013

Tuckerman Ravine has Moderate and Low avalanche danger.  Right Gully, 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. Lobster Claw, the Lower Snowfields, and Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely.

Huntington Ravine has Moderate and Low avalanche danger. Central, Pinnacle, Odell, and South gullies have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. All other areas have Low avalanche danger. Natural avalanches are unlikely except in isolated terrain features.

A benefit of this arctic blast of cold air is when it finally gets tropical….say to about +10F… it will feel so pleasant I’ll want to wear a t-shirt. Until then this abominable devil is embedded in the White Mountains conspiring together to generate sub-zero air.  In addition to the mercury only climbing to -20F on the summits today the wind velocities will exceed 100mph (160kph) in the afternoon.  As yesterday, these arctic conditions will require a lot of experience and the best extreme weather clothing.  Even if you have these you still might be considered a little …well….’off’ to attempt a summit bid.  Seriously though, this weather is brutal and will take advantage of any mistake, so think through your actions today.

A little snow has been blowing around under clear skies this morning.  As winds pick up to the century mark later today more snow will be transported from above treeline into the Ravines.  Some areas may pick up a little and a number of areas may lose a little due to scouring. The 10” that fell over 4 days last week fell under temperatures in the teens and low twenties.  The snow that exists in alpine zones that survived some high winds after the snowfall has been subject to air 40-50 degrees cooler than when it fell. This temperature gradient has undoubtedly created some faceting and weakening of bonds particularly in the more porous pockets distributed in all the nooks and crannies above timberline.  The new snow crystals blowing around are very fine fragmented particles that are re-distributing into dense pockets in some isolated Ravine areas.  This is not an alarming issue right now, but it is my best take to explain the transport of new icy crystals under moderate Washington winds of 60mph.  It will be hard to say what 100+mph winds will do, but be prepared for newly transported icy crystals to be moved into avalanche terrain later today.  You may see some areas move to the upper end of their ratings if this occurs.  Besides this potential issue we continue to have intense spatial variability with a number of areas being subject to obvious scouring as noted by strong visual surface markings, the northern gullies in Huntington are one example.  Left over pockets of instability that haven’t changed much due to the cold air in place, most notably the Lip and it’s immediate neighbors in Tuckerman, are the locations that I am most concerned about.

As mentioned over the past couple of days the old hard surfaces are still causing a traction problem in a number of locales. These old surfaces are camouflaged by newer snow in places and threaten skiers and climbers with long sliding falls.

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 8:23a.m. 1-24-2013 A new advisory will be issued tomorrow.

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

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