Avalanche Advisory for Wednesday, 2-29-2012

This advisory expires at midnight Wednesday, 2-29-2012

Tuckerman Ravine currently has MODERATE and LOW avalanche danger. The Sluice, Lip, Center Bowl, and Chute have Moderate danger.  Natural avalanches are unlikely and human triggered avalanches are possible.  The Lobster Claw, Right Gully, Left Gully, Hillman’s Highway, the Lower Snowfields and the Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features.

Huntington Ravine currently has LOW avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features. 

On this final day of February, in a leap year, the Snow Rangers are celebrating an extra day of winter with the hope it will help our annual snow total.  Wishful thinking you say?  Well read on to hear about the impending storm moving in today.  Over the past 24 hours the summit only received 0.3” of new snow with moderate NW winds which obviously didn’t add to many avalanche instability issues.  All areas dropped a rating from yesterday with the main concerns living in the Center Bowl, Lip, and Sluice.  The fracture lines from last weekend’s storm continue to slowly fill.  This aids us to quickly determine how much these general areas are picking up with a quick look through the binoculars.  Overall, there are some instabilities to recognize today, but the real problems won’t develop until very late in the day with the intrusion of our next weather maker.  A WINTER STORM WARNING is in effect from 7pm tonight to 9pm Thursday evening.  The system moving from the S will give us a chance of afternoon snow before the main precipitation shield envelops the mountains.  Snow totals are expected to be heaviest in the southern part of the state where a QPF (expected water equivalent) of 1.0” is higher than the 0.7” for our region.  One thing the North Country has going for it is colder air, adding to our “fluff factor”, as the NWS calls it.  In total 6-10” of snow is a reasonable expectation by the time it shuts down.  This storm will be delivered on light to moderate S to ESE wind from 10 to 40+ mph.  This won’t have the usual loading factors we see with our prevailing westerly’s so expect Hillman’s Highway, Left, the Escape Hatch, South, and Odell gullies to be our main forecast areas of concern tomorrow.  We will have cross loading issues in some areas, but that will be greatly determined by how high our wind speeds become.  Although the weekend is still many weather model runs away, they currently are highlighting some shifting and increasing wind which are concerns for me.  Winds are expected to stay light to moderate, for Mount Washington, until Saturday when a W or NW will may hit +/-80mph overnight giving us a significant loading event.  More on this potential avalanche issue in the upcoming days. 

Summarizing, in areas at Low danger you will find old surface with numerous pockets of softer snow which can be easily avoided by a skier, rider or climber that’s paying attention to the terrain.  Areas at Moderate harbor more issues due to the last 3 days of loading and 1.7” of snow.  The winter storm will start giving us snow this afternoon but should not affect avalanche danger today during daylight hours if the forecasted timing is on the mark.  Be ready to adjust your plans if it begins earlier than very late today.  The intensity will pick up during the early morning hours with up to a few inches on the ground by dawn.  Snow will fall through Thursday increasing the avalanche danger.  Expect “Considerable” or higher to be issued in tomorrow’s advisory.

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 8:35a.m. A new advisory will be issued tomorrow.
 

Christopher Joosen, Snow Ranger     
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856
www.mountwashingtonavalanchecenter.org

2012-02-29 Print Version

 

Avalanche Advisory for Tuesday, 2-28-2012

This advisory expires at 12:00 midnight, Tuesday, February 28 2012.

Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. The Sluice, Lip, Center Bowl, and Chute have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Lobster Claw, Right Gully, 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.

All forecast areas of Huntington Ravine have MODERATE avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. 

Today is a day of changing avalanche danger. Yesterday’s weather forecast for 1-3” didn’t quite pan out as we had hoped, with just 1” of silky 10% density snow falling at Hermit Lake. This is OK, though, because any snow is better than no snow this season. Late yesterday morning, winds began to transport snow around Tuckerman Ravine. This snow was leftover from the weekend storm and was made available for loading by a slight shift in wind direction. Fracture lines in the bowl were refilling even before any new snow began to fall. Later in the afternoon, when light snowfall started, the winds also began to accelerate. This trend has continued to the present time, with winds blowing even stronger than the morning forecast (currently gusting over 100mph/162kph) and light snow flurries still in the air. All this is adding up to the idea that there is sufficient loading taking place at this time that you should be thinking about naturally-triggered avalanches being possible in some locations. The Sluice definitely has my attention, since we believe it did not avalanche during the weekend cycle while slopes on either side of it did. Adding another layer of new slab on top might be just the load it needs to fracture and fail. As I mentioned in yesterday’s advisory, getting into an avalanche in the Sluice would carry severe consequences due to the terrain traps in the runout below. Additional loading on the bed surface in the Lip and Center Bowl could also produce naturally-triggered avalanches today.

The changing part of this forecast has to do with the high pressure system that is expected to take hold and clear the mountain of its foggy shroud. As this moves in, wind speeds will be decreasing, which is a two-sided coin in this situation. Current wind speeds are doing a good job of scouring new snow out of many forecast areas, but as speeds diminish, the rate of slab development will increase. This will continue either until there is no longer any snow available for winds to move, or until wind speed drops off significantly. The safe bet today is to expect further wind loading to be taking place until visibility improves and shows you that the loading is over. By the end of daylight hours, I think the Considerable rated areas will have dropped down into Moderate territory, but that still means there is the possibility of a person triggering an avalanche. I also think there might be some areas of Huntington and Tuckerman that won’t hold onto much new slab. If this is the case, late in the day the hazard in these areas would be dropping as well. Until visibility improves, you won’t be able to determine whether or not this has happened. Basically, if you’re staying on the hard old surfaces you’ll avoid instabilities altogether.

I had the not-so-fun experience yesterday of trying to ride a snowboard out through the Little Headwall. Attempting this in its current state will put you into bushwack to avoid the open streambed, followed by a couple turns on the Little Headwall to avoid the open water hole, then down into slightly more open bushes down below. You’re not missing much by taking the hiking trail down. Maybe some new snow on Wednesday night and Thursday will change things here, but I’ll believe it when I see it.

 

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 8:35am. A new advisory will be issued tomorrow.

 

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

2012-02-28 Print Friendly