Avalanche Advisory for Wednesday, February 5, 2014

Expires at Midnight.

Tuckerman Ravine has CONSIDERABLE avalanche danger.  Natural avalanches are possible and human triggered avalanches are likely. Dangerous avalanche conditions exist and conservative decision making is essential.  The only exception to this rating exist in the Lobsterclaw, Right Gully, the Lower Snowfields and the Little Headwall which have Moderate avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible.

Huntington Ravine has CONSIDERABLE avalanche danger.  Natural avalanches are possible and human triggered avalanches are likely. Dangerous avalanche conditions exist and conservative decision making is essential.

AVALANCHE PROBLEMSStorm Slabs and Wind Slabs will pair up and dominate the avalanche problems today.  The current winter storm will create widespread instabilities complicating the Wind Slabs and Persistent Slabs that made up the snow pack issues as of yesterday.  These should be kept in mind, but should come as a distant second to the new slabs that will build creating the possibility of natural avalanches.  Also expect frequent new loose snow sluffing

WEATHER:  A WINTER STORM WARNING is in effect for the State.  Snow began on light WSW winds between 2 and 3 am this morning.  Snow intensity is expected to increase giving us up to an inch an hour later this morning.  5-7” are forecasted for today with an additional 2-4” tonight, the vast majority of which should fall by midnight.  A wrap-around upslope snow potential should linger thereafter giving us a bit more.  Currently winds remain right around 16mph from the SW.  These velocities should increase slowly through the day as winds walk counterclockwise around the compass rose moving through the S, ending up out of the E later today.  Speeds are forecasted to build to 30 and gust higher before increasing some more as they march through the NE, N and resting out of the NW overnight.  Models and forecasts often undershoot the “fluff” factor in these cold storms so be prepared for potentially more inches of lower density snow with the same water equivalent.

SNOWPACK:  Although instabilities that existed prior to today may factor into the size of avalanche activity by stepping down into these weaknesses, the bulls-eye focus should stare right at today’s new storm snow.  A very light southerly wind coupled with low density snow, likely in the 4-6% range, will work together to create touchy soft slabs.  These will predominately be found high in the start zones of slopes with a north facing component.  These slopes will be knocking on the door of a High danger rating.  Namely, areas such as Left gully and Hillmans Highway in Tuckerman as well as Odell, South and the Escape Hatch in Huntington. All of these locales will move to the upper end of the Considerable definition.  Slopes pointing to the S will become cross-loaded by E winds later.  Gullies such as Damnation, Yale and the Sluice will be some of the last locations to reach today’s rating.  In storms like this, as winds wrap through the event, it is very important to pay close attention to the slight cross loading nuances.  Although some locations may have a generally E facing component, the nearby terrain features allow them to be cross loaded.  Some classic examples include the Chute in Tuckerman and Pinnacle in Huntington.

The bottom line today: Expect slabs to possibly fail naturally today within the new, low density, snow above the interface with the old surface.  Anticipate slabs to increase in density as winds pick up through the day.  This will occur first on N facing slopes followed by S facing areas later.  Natural avalanches in new snow may overload deeper weaknesses and steep down, creating a larger avalanche.  Generally, the widespread peak instability should occur after dark.  It is quite plausible we will reach a “High” rating in some locations very late tonight or early tomorrow morning.  Expect an elevated avalanche danger tomorrow.

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 810a.m. 2-5-2014. 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

2014-02-05 Print