Avalanche Advisory for Friday, March 7, 2014

Expires at Midnight

Tuckerman Ravine has Moderate avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully.  The Little Headwall has Low danger.

Huntington Ravine has Moderate and Low avalanche danger. Yale, Central and South Gully 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.

AVALANCHE PROBLEMS: Persistent slabs and wind slabs are jockeying for position as our primary avalanche problem today. The variability in our upper snow pack presents a range of hazards in our terrain. Careful route finding and continuous snowpack evaluation can make it possible to travel safely in gullies with a southerly aspect. The uncertain stability of deeper persistent layers in the upper 1 meter of the snow warrants careful travel techniques and the proper gear. Afternoon and evening wind forecasts hold the potential to quickly load start zones so keep an eye out for this loading. Warming today will weaken areas of surface wind slab on the steepest south facing terrain.

WEATHER: 2.7” (5.2cm) of snow which fell on Tuesday night and Wednesday is still laying around due to light winds since then.  Southerly aspects dampened in the strong solar radiation yesterday though cold ambient temperatures slowed heat gain and stabilization deeper in the snowpack. Clear skies and warmer ambient temperatures near 20 F today will continue some heating of the snowpack though winds this afternoon will offset this heating to some extent as they ramp up. Some loading and sluffing was observed this morning in Central and Yale. Winds are forecast to reach 50 mph later today, gusting higher this evening.

SNOWPACK: Light winds over the past several days laid a tempting blanket of fresh snow in lee areas. These surface slabs were reactive yesterday and easily broke out at switchbacks and steep rollovers and failed on isolation in stability tests, especially where they thinned out at the edges of pillows. Right Gully has benefitted from skier compaction in the last couple of days but lingering, larger pockets on the hikers left side deserve respect.  The new wind slab was inverted and likely to be much deeper moving through Sluice to Center Bowl and Chute were sastrugi in the upper steep sections indicate minor scouring with deposition below the ice in the bullseye mid-section of those start zones. That said, folks enjoyed fine ski runs in the new snow and soften ice crust on the lower angled terrain, out of the runout, between Lobster Claw and Right Gully. Stability tests in Sluice area showed the existence of a weak layer of needle forms lingering since late last month which produced clean shears in the moderate range (CT11-14). Due to the depth of this weakness, this layer has my hackles up as much as any other since it is close enough to the surface to trigger but deep enough and not obvious enough to go unnoticed when digging hand pits or probing with an axe or pole. Other interfaces exist in older finger hard wind slabs before you reach the pencil hard wind slabs deeper down which are mostly bombproof. A couple of these shallower layers in the snow failed high in the hard range but produced clean shears so remain capable of avalanching. With a nice weather forecast for today and possible for the weekend, I am expecting a lot of climber and skier traffic so look out for others above you and be respectful of those below you. Cold temperatures at night and in shaded areas are continuing to put the stabilization process on hold with very cold snow temperatures. 4” (10cm) down from the surface yesterday, on a south facing slope in the early afternoon, snow temperatures were still only -12C, though the surface 2” of snow was moist.  Reducing your exposure to avalanche paths when traveling un-roped or skiing, protecting yourself when roped and using solid micro-route finding skills remains key.

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 8:40 3-07-2014. A new advisory will be issued tomorrow.

Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2014-03-07 Print friendly