Avalanche Advisory for Wednesday, April 6, 2016

This advisory expires at Midnight

Tuckerman Ravine has MODERATE avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Heightened avalanche conditions exist on specific terrain features.  Be sure to evaluate snow and terrain carefully to identify areas of concern. Lobster Claw, Lower Snowfields and Little Headwall are not posted due to lack of snow. Huntington Ravine is posted under a General Bulletin for the remainder of the season. You will need to do your own snow stability assessments when traveling in avalanche terrain in Huntington Ravine. A danger of falling ice exists, and will persist until it all comes down.

AVALANCHE PROBLEM: Today’s avalanche problem continues to be Wind Slab.  The 5-6″ (12.5-15cm) of low density snow that fell on Monday was delivered on moderate winds allowing for widespread wind slab to develop. Expect the most sensitive wind slabs to human triggers to be in the strong lee of mid-elevation Ravine terrain features such as under the Lip, under the Headwall, and above the narrows in the Chute

WEATHER: Through snowfall on Monday temperatures remained cold.  This trend has continued since snow ended Monday evening keeping the mercury below zero F on the summit of Washington. (BBBRRRR! Ah the variability of April!)  Today, temperatures will rise substantially, albeit only into the mid-teens F, as the next weather maker approaches, potentially delivering light snow by very late in the day.  This precipitation will transition through a variety of types overnight and through Thursday.  At some point tomorrow expect rain on Wind Slabs before moving back to snow Thursday night.  This forecasted 1.0-1.3″ of total melted liquid may fall heavy at times as snow, sleet, freezing rain, and rain so anticipate a messy day tomorrow.

SNOWPACK: 8.1″ of new snow fell on the summit between Saturday and Monday. The majority of this fell on Monday as 3% low density snow, on a shifting moderate summit wind, between 20-35mph. In protected lee areas of W and NW winds expect the initial low density snow to act as the weak layer for slab that built later in the snowfall event, and into Tuesday as winds increased. Although the summit was in the clear by yesterday’s maximum wind period, an afternoon peak of 73mph influenced many of the aforementioned protected areas to some degree.  Therefore, expect slabs of increased density over areas of lower density slab, some of which may be quite sensitive to human triggers.  Due to the low density Monday snow, and the varying degree of terrain influences, be prepared for a high degree of weakness variability.  Based on your stability tests you may feel comfortable traveling in new snow, but be careful moving into unrecognized dramatically weaker snow where it was less influenced by winds, such as close to dominate terrain features.  I.e. buttresses, the main Headwall, rollovers such as the Lip, etc. The cold temperatures has kept snow pack consolidation and stabilization slow.  So although you notice we have dropped the danger rating from yesterday, this is mostly due to the natural avalanche potential falling from possible to unlikely.  Today’s Moderate danger rating, having just crept below the Considerable line, still has a fair amount of concern for human triggers.  Evaluate snow and terrain carefully and be quite wary of others in the terrain that may trigger slabs above you or propagate over to your location.  Also think about what runout paths you are in as you consider wandering up the Tuckerman floor.

The same winds that loaded our terrain with snow have also scoured some areas, leaving the old rain crust visible. Arresting a fall on this hard layer of icy snow will be next to impossible. Long sliding falls can be disastrous, particularly if they take place above a rocks or an open crevasse. The Sherburne Ski Trail is now closed about a third of the way down. Please cross back over to the hiking trail at the rope and walk to Pinkham.  Expect new snow to hide vast amounts of water ice on the hiking trail. The Harvard Cabin is closed for the season. The only camping permitted on the east side of Washington in the Cutler Drainage is at Hermit Lake Shelters.

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.
  • Posted 7:00 a.m., Wednesday, April 6, 2016. A new advisory will be issued tomorrow.

Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2716