Avalanche Advisory for Wednesday, January 22, 2014

This advisory expires at midnight.

Tuckerman Ravine has Moderate and Low avalanche danger. The Sluice, Lip, Center Bowl, Chute, and Hillman’s Highway have 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 except in isolated terrain features.

Huntington Ravine has Moderate and Low avalanche danger. Central, Pinnacle, Odell, South, and Escape Hatch have Moderate avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible. North, Damnation, and Yale gullies have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features.

AVALANCHE PROBLEMS: Human triggered Wind Slabs are the main concern today.  Areas posted at Moderate have larger areas of new wind slab; areas posted at Low danger may also have unstable wind slab, though they are smaller and more isolated throughout the gully or snowfield.  Expect an intense amount of spatial variability.  Cold weather is dramatically slowing this wind slab problem from stabilizing. Tomorrow we may start considering slabs in place as Persistent Slabs.

WEATHER: Temperatures continue to be very cold today with a high of about -10F (-23C), dropping to -15F (-26C) tonight.  Winds speeds from the N are expected to increase through the day, perhaps gusting over 50mph this afternoon.  The high pressure is presenting us with a dry, 22% relative humidity, air mass and no real precipitation in the extended forecast.  As was discussed yesterday the avalanche problem you’ll be facing today is a result of recent weather history.  Over the past several days 4+” (10+cm) of new snow was loaded into the Ravines from predominantly westerly winds, with gusts as high as 95mph (153kph).

SNOWPACK: There is a lot of spatial variability in areas both rated at Low and Moderate.  Over the past 28 days we have had 24 days with recorded snow, but the dramatic swings giving us rain and warm temps have crushed this joyful news. However, over the last 10 days since rain, cold air, upslope snow, and a storm event has produced 15.5” (38cm) of snow.  This snow has been loaded in from all points of the compass rose, predominantly from the W and NW.  You will find icy old surfaces from the Jan 11th rain event with dry slabs on top, knee deep or more, within half a rope length.  This classic Mount Washington scenario can be found in numerous locations.  A good example of this is in Tuckerman’s Left Gully where hard old surfaces play leapfrog with newer slabs as you move up and down as well as side to side.  With some clearing sky conditions and cold air we will be on the lookout for facet development.  This will develop weak layers within the existing slabs causing a persistent slab concern.

There are days “Low” can mean rock solid everywhere, while at other times we have concerns about isolated pockets of unstable slab.  These instabilities within isolated terrain features can certainly be problematic.  Their actual stability can be similar to the slabs in areas posted at Moderate, but they are not consistently found throughout a forecast area, or are easily negotiated around and can be avoided with little difficulty.   Low is often used when these isolated areas are obvious to determine such as the difference between old rock hard ice, peppered with isolated slabs.  An example of this is high up in the Huntington’s northern gullies which have scant snow coverage.  But there are snow instabilities here that you should be on the lookout for. Good route-finding in these gullies will go a long way to keeping you out of harm’s way.

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 755a.m.1-22-2014. 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

2014-01-22 Print