Avalanche Advisory for Saturday December 28th, 2013

This advisory expires today at midnight.

Tuckerman Ravine has CONSIDERABLE and LOW avalanche danger.   The Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway have Considerable avalanche danger today. Natural avalanches are possible and human triggered avalanches are likely. Lobster Claw, Right Gully, Lower Snowfields and Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely.  These Low areas are mostly a bushy rocky landscape lacking any sizable slopes for unstable slabs or traveling.

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger.  Central, Pinnacle, Odell, South and Escape Hatch have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. North, Damnation and Yale have Moderate avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible.

AVALANCHE PROBLEM:  Today we continue to have a combined avalanche problem of Storm Slabs and Wind Slabs.  An additional 2” (5cm) last night brings the recorded summit total to 10.5” (26cm) over the past 48 hours.  Through Saturday another 1-3” (2.5-7.5cm) of snow is forecasted which will be adding to our stability issues today.  As temperatures climb new snow density will rise contributing to denser slab development over the lighter layers from yesterday.  Moderate to high winds have loaded in snow from above treeline mixing with snow falling from the sky. This developed slabs predominately in our strong lee areas that have an E facing component due to mostly a W wind.  This main concern is followed by aspects facing NE and SE.  It will be important to constantly assess stability as you move because you will find a lot of variability.  This runs the spectrum from scoured hard surfaces generally down low and in the open, to new slabs generally in higher regions in Tuckerman and often lower in the Huntington approaches.

WEATHER: Light upslope snow continued on and off through the night delivering an additional 2” (5cm) totaling 10.5” of 6.2% density over the past 48 hours.  W winds from 50-70mph yesterday have ticked up this morning and are expected to move into the 80’s over the next few hours before subsiding later.  An additional 1-3” of snow is expected today which will mix in with drifting snow from alpine zones creating more unstable snow.  A Winter Storm Watch is in effect for Late tomorrow into Monday morning.

SNOWPACK: This upslope event with cold air in place and a wind that has gone up and down over the past 2 days has given us a number of new concerns.  Slick bed surfaces before the snow onset on Thursday were loaded with a moderate wrapping wind starting us out with low density slabs on an icy layer.  Moderate to high winds since continue to load a number of strong lee areas with thicker slabs.  Although we are still socked in with clouds and blowing snow we believe you will find quite spatially variable conditions as you move around.  A number of areas are likely scoured down to old surfaces due to high winds, icy old bed surfaces, and low density snow.  You will also find unstable new Storm and Wind Slabs in protected terrain.  In some locations it may include the majority of the forecast area such as in the Center Tuckerman Bowl. In others it may only be in one location, but that may be enough such as the approach to Pinnacle’s first pitch in Huntington.  The only consistent factor is the nature of any slab failure today.  You will find shear failure within new snow likely in lower density slab that was deposited during periods of lower wind speeds.  Depth of this failure is going to be quite variable depending on location.  In our bottom line forecasters discussion this morning we felt we are closer to natural avalanches be possible than unlikely due to increasing wind speeds and up to another 3” (7.5cm) of snow today.

Icy conditions still exist. Crampons and an ice axe are required for safe travel in steep terrain and other traction footwear for travel on low elevation hiking trails.  New snow will hide slick sections as well as rocks and holes between rocks.  Recent new light density snow will amount to less than 6″ from Hermit Lake down the Sherburne and will hide rocks, water ice and death cookies of refrozen crust. Sherburne ski trail coverage is very thin. Long sliding falls are possible. Realize that in locations scoured by high winds, and in locations where snow is thin, the icy surface with be hard to self-arrest on making it very difficult to stop yourself if you fall.

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 0828. 12-28-2013. 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

2013-12-28 Print