Avalanche Advisory for Monday, January 25, 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: Today’s primary avalanche problem continues as windslab. These firm slabs, formed during the period of high winds last Tuesday through Thursday, have proved to be unreactive so far. They are thick enough in most places to create a strong bridge over the potential weak layers residing underneath. With a snowpack that is still quite shallow for late January, there are plenty of terrain features that have only recently disappeared under the snow. It could be possible to initiate a crack in these areas of thinner coverage, particularly in the steep areas of the Lip and Center Bowl.

WEATHER: Yesterday was one of those mid-winter days on Mount Washington that makes one feel as though they’re no longer in the Arctic. Sunny skies prevailed with temperatures rising into the high teens F. Temperatures look to remain in the teens through today along with decreasing winds. Some clouds will linger this morning but by afternoon they should dissipate bringing on another sunny day. A warm front is approaching with a possibility of snow for tomorrow morning and the ensuing low pressure system to produce a sharp increase in winds. Be alert for an increase in avalanche hazard for tomorrow. We have received no new snow since the sustained period of high winds last week.

SNOWPACK: Today’s low rating derives from the strength of the windslabs. This windslab, very thick in areas like Left and Right Gully, the Sluice and the Chute, is the top layer of the snowpack. Beneath this layer of pencil-hard windslab is a softer layer of windslab (primarily 1F). One potential bed surface for an avalanche is the ice crust formed two weeks prior from the rain event on January 11. With colder nights recently, faceting is taking place near that bed surface as well as within the 1F layer sandwiched in the middle. Yesterday’s and today’s milder temperatures may encourage the sintering process, though despite the bright sun, the snowpack was not heating up due to solar radiation. This all points to a surface layer of windslab that is quite strong, but there is the potential to find the thin spot where closer-to-surface faceting combined with a traveler’s weight could produce a fracture. These thinner areas are likely to found in steep terrain like the Lip and Center Bowl, areas that take much more snow to fill in.

Huntington Ravine remains under a General Bulletin. It is important to remember that avalanches can occur under a General Bulletin. The biggest potential areas are the snowfields in Central and South Gully as well as at the base of the ice in Pinnacle and Odell’s. The northern gullies of Yale, Damnation, and North are primarily ice and contain very little snow. The Lion Head Winter Route is now open. Bear in mind this is not a hiking trail and mountaineering sense should be in your backpack, right next to you crampons and ice axe. The Sherburne Ski Trail is skiable top to bottom and is seeing a fair amount of traffic. This traffic is pushing snow to the sides, revealing a good amount of water ice and rocks that were covered. Expect challenging conditions.

2016-01-25