Avalanche Advisory for Saturday, January 23, 2016

All forecast areas of Tuckerman Ravine have LOW avalanche danger.  Natural and human triggered avalanches are unlikely.  Watch for unstable snow in isolated areas.  Lobster Claw, Lower Snowfields, and the Little Headwall are not posted due to lack of snow cover. Exercise caution in these areas.

Huntington Ravine is under a General Avalanche Bulletin. General Bulletins are issued when instabilities are isolated within forecast areas and are issued every three days or earlier if conditions warrant. Forecast areas in Huntington have less well-developed snowfields to produce avalanches than Tuckerman, but understand instabilities in these smaller locations may exist.  It is critical that you assess snow and avalanche conditions if venturing into Huntington.

AVALANCHE PROBLEM: Wind slabs continue to be the primary avalanche problem.  The high winds this week have packed and battered most snow covered slopes into firm hard wind slab.  The majority of snowfields could be categorized as pencil (P) hard over softer 1 finger (1F) hardness in most locations.  This step change can be characterized as being fairly deep, often found 0.7 meters or more from the surface.  I would consider this “deep” based on the overall strength of P and P+ slabs. Current slabs can be described as mostly resistant to human triggering due to both bridging and the fairly strong bond at the hardness transition. The possibility of triggering these slabs is low, but consider spatial variability and look for some isolated instabilities in small pockets, such as near the Sluice and the traverse over to the Lip. Buried terrain features that are hard or impossible to locate like rocks and bushes may also have weaker snow around them.

WEATHER: Today’s weather won’t quite be the best we can see, but should be pleasant for winter activities on Mount Washington for the prepared.  A very light E and NE wind will gradually build today, eventually climbing towards 40 mph (64kph) late in the day.  This is coupled with a fair amount of cloud cover, but the summits are expected to remain clear with the mercury rising into the teens F.  This general theme will continue through the weekend, although winds will shift around from the W by tomorrow with a slight uptick in velocity.

SNOWPACK: Yesterday’s field assessments and analysis allowed us to drop all areas to “Low” avalanche danger in Tuckerman.  Digging, poking and prodding in Right Gully, the Sluice, the Chute, and Left Gully delivered a pretty consistent theme for us yesterday afternoon.  Firm P+ to P hard slopes near the surface, that are fairly strong, exist in the majority of locations.  As you dig you are likely to find softer snow to Finger hardness (F+ to F-) beneath, but the depths will vary tremendously as you move around.  This depth variability should cause more concern if hard over soft slabs are seen near the surface.  This is based on your weight being more likely to impact them then if found deeper. However, we found that the transitions in hardness, often considered a potential failure layer, were either deep or bonding well. We walked away feeling the overall strength of wind slabs were good, making the move from Moderate to Low avalanche danger appropriate.  Although the proverbial arrow has pointed more towards green than red, be cautious and make thoughtful choices based on data observations and not desire. Expect spatial variability and isolated pockets of instability so as always make constant assessments and risk evaluations.  A small pocket high on a route has very different ramifications generally than one that is lower.

Huntington Ravine, while under a General Bulletin, may harbor some wind slab issues such as at the base of Central, Pinnacle and scattered through Odell and South gullies.  Good visuals show that the northern gullies have limited snow coverage so expect to find long stretches of low angle ice.  The Lion Head Winter Route is now open and is recommended for those opting to avoid avalanche terrain in the early season. Mountaineering skill and proper equipment, such as crampons and an ice ax, are essential. Microspikes are not adequate for this route or any other accessing treeline.  This route opens annually when the Lion Head Summer trail snowfield traverses grow enough to become an avalanche hazard.  The John Sherburne Ski Trail is moving into survival skiing in many locations as it becomes harder each day with rapidly growing water and alpine ice. Expect challenging conditions.

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 8:30 a.m. January 23, 2016. 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

2016-01-23