Avalanche Advisory for Saturday, January 30, 2016

Tuckerman and Huntington Ravine have MODERATE avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible.  Heightened avalanche conditions on specific terrain features exist. Evaluate snow and terrain carefully to identify features of concern.  Lobster Claw, Lower Snowfields, and the Little Headwall in Tuckerman and North, Damnation, Yale and the Escape Hatch in Huntington are not posted due to lack of snow cover. Exercise caution in these areas and expect the potential for isolated patches of instability particularly around pitches of water ice.

AVALANCHE PROBLEM: New Wind Slabs are the primary avalanche problem today.  New snow with initial low winds that became much higher has created new soft slabs that should be reactive to human triggers in protected lee slopes.  This is especially a concern high in both Ravines and below steep areas that have sluffed off, like near the base of steep water ice. Additional snow tonight and Sunday night will likely leave Wind Slabs as a threat through the weekend.

WEATHER: By midnight the summit received 3.7″ (9cm) of 8% snow with several more hours of lingering snow showers before shutting down very early this morning.  Winds speeds increased through the evening from the WNW at approximately 50-60mph (80-96kph).  This morning winds are beginning from the WNW, but should shift through the W to the WSW or SW this afternoon and then progress back to the W late, all the while increasing. The mercury, starting in the singles this morning, will climb close to 20F (-6.5C). Overnight winds will exceed hurricane force gusting to 90mph (144kph) on the summit, with another 1-3″ (2.5-7.5cm) of snow expected. Tomorrow winds will diminish, after early high velocities, with temperature rocketing above freezing.

SNOWPACK:  The vast majority of your snow focus should pay attention to the new 4″ (10cm) of snow overnight and the instabilities it likely produced.   This precipitation began yesterday afternoon on very light winds which plausibly created a thin unconsolidated weak layer of light density snow.  As winds picked up with additional snow, soft slabs with an increasing density likely developed, particularly higher in the start zones and lower beneath steep sections.  I would be looking for thin touchy slabs in sheltered locations that are protected from the effects of WNW, W, and WSW winds.  The base of ice pitches is a classic location in both Ravines to find instabilities due to being sheltered from scouring and all the sluffing snow that builds up into thicker slabs.  Due to sluff pounding you will usually find these are denser slabs as well.  Snowfields from the Lip, across the Tuckerman headwall, to Left Gully are some specific locations to harbor new unstable slabs. You will also likely find variable conditions with some exposed locations blown clean to the old surface.  These will likely be very hard so crampons and an ax will be an essential part of your equipment.  Sections of dust on crust may also hide the lurking stiff layer below.

A number of slopes, particularly with an E facing aspect, will be bumping the ceiling of the Moderate rating later today.  As we move into darkness and slabs grow I would have a greater concern for natural avalanches probably crossing over towards a Considerable rating during the overnight.  Although we generally feel the old hard slabs that have been with us for a while are strong to human triggers it is certainly possible that an over running new slab avalanche could step down into this deeper hard slab. Very high winds tonight and additional forecasted snow will increase the avalanche danger into tomorrow morning. Expect hurricane force winds to move a lot of snow from the alpine zone into Tuckerman and Huntington exacerbating the situation.

The Lion Head Winter Route is open and is recommended for those opting to avoid avalanche terrain in the early season. Microspikes and ski poles are helpful on lower elevation trails, but are not substitutes for crampons and an ice axe on this route. The John Sherburne Ski Trail is passable but has become harder with expanding water ice each day. This issue can be added to many waterbars and occasional rocks. Very thin new snow will likely hide some of these demons. Expect very challenging conditions.

Please Remember:


Posted 8:18 a.m. January 30, 2016. A new advisory will be issued tomorrow.

Christopher Joosen, Snow Ranger
USDA Forest Service
White Mountain National Forest