Avalanche Advisory for Monday 3-4-2013

This advisory expires at 12:00 midnight.

Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger today. The Lobster Claw, Right Gully, Sluice, Lip, and Center Bowl will have Considerable danger. Natural avalanches are possible and human triggered avalanches are likely. The Chute, Left Gully, Hillman’s Highway, and the Lower Snowfields have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The Little Headwall has Low avalanche danger. Natural and human triggered avalanches are unlikely.

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger today. North Gully, Damnation, Yale, and Central Gully will have Considerable danger. Natural avalanches are possible and human triggered avalanches are likely. Pinnacle, Odell, South, and the Escape Hatch have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.

Due to the forecasted weather for today, avalanche danger is once again posted at Considerable and Moderate. This is the same scenario as in the previous two days. The current conditions on the ground fall into the Moderate range this morning, but we expect increasing danger as 1-3” of new snow falls and winds are able to load this snow into avalanche starting zones. If you’ve read the last couple of avalanche advisories, you may think I’m sounding like a broken record. Or, if you were on the mountain looking at conditions late yesterday afternoon, you probably think I sound more like Chicken Little. Neither Saturday nor Sunday did the potential for increasing avalanche danger really pan out, so the snowpack never really reached the Considerable rating. However, my confidence in this happening today is greater than either of the past two days.

Last night winds hit a maximum speed of 55mph from the NW. This is a stronger speed than we’ve seen since the Nor’easter 4-5 days ago. Since that storm, we’ve received a couple dustings of new snow which had been sitting almost undisturbed in steep terrain across the mountain. For example, in Right Gully yesterday there was a very uniform 1” (2.5cm) layer of loose snow sitting on top of denser windslab. This was present all the way from top to bottom, which is unusual for this mountain. Now the winds are finally going to be able to move some of this snow into the ravines. Last night’s winds, plus new snow and additional wind loading from increasing N winds today, will load slab on top of this layer and add greater complexity to the snowpack. You should expect avalanche danger to be on the rise today, particularly on S and E facing slopes such as Right Gully, the Sluice, Lip, and Center Bowl in Tuckerman; and North,  Damnation, Yale, and Central in Huntington.

The complexity of the snowpack is interesting. On S-facing slopes, you will find numerous sun crusts, but you would have a hard time finding them on other aspects. Despite being slightly older, the slabs sitting above and between these crusts on S aspects are cohesive enough to propagate fractures, and the crust are becoming more fragile over time. Our snowfields have been growing in size and becoming more interconnected, and potential avalanche runout distances have lengthened. All of this is conspiring to make safe travel in avalanche terrain more challenging. You best bet for more straightforward route-finding is in areas such as Hillman’s, Left Gully, or South Gully.

 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 8:00 a.m., March 4, 2013. A new advisory will be issued tomorrow.

Jeff Lane, Snow Ranger
USDA Forest Service
White Mountain National Forests
(603) 466-2713 TTY (603) 466-2856

2013-03-04 Printable