Jan 302013
 

Expires at Midnight 1-30-2013

Tuckerman Ravine will have CONSIDERABLE avalanche danger today.  Natural avalanches are possible and human triggered avalanches are likely.

Huntington Ravine will have MODERATE avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible.

Expect an increasing avalanche danger today.  Boy is there a lot to talk about today so let’s jump right in shall we.

WEATHER:  On the way up to Hermit Lake today I hit a wall of “hot” air at about 3000 ft that made me wonder if I had stumbled upon So.Cal’s Santa Anna breezes.  It cooled off a bit at 3800ft to 43F (6.2c) but climbing.  Avalanche terrain will see the mercury rise into the high 40’s, and perhaps beyond, as the brunt of precipitation bears down on the region.  What never ceases to amaze me is Washington’s swing in weather conditions.  When I left the mountain on Sunday the previous 11 days on the summit had an average low of -19.7 F (-29C) with the lowest point being -35F(-37C). Today the summit should hit the mid 40’s a swing of 80 degrees in a week!  Imagine it being 100 F at your house and a week later it’s 20.  The chance of rain will also increase through the day and will be likely this afternoon.  Valleys to the south of the Presidential Range are forecasted to receive 0.9 to 1.2” of rain while north a little more, between 1.0 and 1.45”, over the next 30 hours.  Most of this amount is expected overnight after dark.  Winds are also anticipated to ramp up as the front brings more precipitation gusting into the 90’s mph this afternoon and over 100 tonight.  As rain trails off the mercury is expected to collapse freefalling sending temperatures deep into freezing territory again tomorrow with snow!  I think I’m getting dizzy. More on that weather tomorrow.

AVALANCHES:  Warm temperatures are creeping their way into the snowpack, albeit slowly.  The snow was so cold from the past week it’s been a little slow to change not affecting stability quite as quickly as usual.   Take a look at a video we posted yesterday on our weekend update page with Jeff showing us some of the weak layer concerns.  Some locations have these issues a little deeper and others a bit closer to the surface, but the clip shows us some average depths.  My mind today is focused on what Jeff points out: slabs sitting on top of faceted crystals nearer to the surface and more developed facets, towards 2mm in size, a bit lower.

Slab strength will decrease through the day as warmth penetrates deeper into the slab, but as off 7am the T10 (snow temp 10 cm below the surface) temperature was still -3.6C at Hermit Lake.  This is quite a bit warmer than yesterday’s -8.2C however shows how slowly changes are occurring in the upper 4” of snow even with such warm air.  The game changer will be RAIN!  As rain moves in and takes hold of the mountains later today heat will be added to the snowpack rapidly.  Rain adds weight, brings freewater into the snowpack melting bonds that were adding strength, and may pool on more impermeable layers.  These all lean to an increased potential for natural avalanche activity.  Expect instability to rise through the day and tick up quickly when rain settles in.  Huntington is a rating lower than Tuckerman because the snowfields are much smaller which requires more instability to avalanche naturally and is also holding less pockets of snow due to intense scouring.  With this said both Ravines will be bumping the upper end of the Moderate and Considerable forecasts with the onset of consistent rain.  Peak instability will probably occur overnight as rain approaches 1.0” of accumulation.  As rain changes to snow we may have entirely new complications, but I’ll wait until tomorrow to get into that.

OTHER PROBLEMS:  1. Expect to need floatation getting off trail later today as post holing may become an issue. Ski’s, Splitboards, and snowshoes will be essential.  2. Climbers should expect the development of ice dams under hydraulic pressure beginning tomorrow.  3. We should begin seeing rapidly developing facets as cold air envelops the Ravines.  This should be most recognizable under new thin pockets of new snow that will deposit on the old surfaces that will be harboring wet snow at 0C.  We will be watching for this as a new weak layer.  4.  Hypothermia at 40F, rain and blowing near 100mph is pretty easy to get.  Think through above treeline travel today and certainly have the best in alpine clothing.

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 8:40a.m. 1-30-2013. 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

2013-01-30 Print Version