Avalanche Advisory for Friday 1-27-2012

This advisory expires at midnight Friday 1-27-2012

Tuckerman and Huntington Ravines have HIGH avalanche danger today.  Natural avalanches are likely and human triggered avalanches are very likely.  Very dangerous avalanche conditions exist and travel in avalanche terrain is not recommended. This includes runout paths of avalanche activity such as the fan in Huntington and the floor of Tuckerman Ravine. The Lobster Claw, the Lower Snowfields, and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when conditions warrant.

As expected, we are in the middle of a winter weather maker with about 6” (15cm) on the ground as of 7am. Light snow began just after dark last night and continued through the evening.  Icing has been mixing with new snow beginning to increase densities causing an inverted snowpack giving us stability concerns.  Additionally, loading has occurred from a southerly direction in the 35-45mph (50-72kph)  range over the past 12 hours, this will start shifting and come from the West and increase.  By late in the day wind speeds should be gusting over 60 mph (100kph) from a westerly direction.  Our main concerns through the morning are focused on aspects that have a northern component due to the overnight loading from the South.  As winds shift and increase they will have a larger pickup zone, namely Bigelow Lawn and the Alpine garden, to load the Ravines directly due to their overall Eastern facing direction.  Some cross loading will occur later today on South facing aspects, but locations like the Right Gully in Tuckerman and Damnation and North Gully in Huntington will hit the High rating later than other forecast areas.  Complicating and accelerating today’s instability issues is the transition from snow to….yup…rain.  The summit is expecting a high of about 30F at 6288 and the Conway valley areas are expecting 40-41F early in the afternoon.  There is a good chance we will see rain develop in our primary avalanche terrain between 4000 and 5200ft.  As precipitation moves from snow, to sleet, to freezing rain, to rain it will add load and stress to the new snow and slabs already on the landscape.  When rain begins you should expect a rapid rise in instability and the likelihood of naturally triggered avalanches.  Rain adds load, melts bonds that were contributing to slab strength, and can percolate down to a buried crust, lens, or blue water ice and lubricate this potential bed surface. 

All of these new issues today are falling on a 1” (2.5cm) crust with recrystalized facets underneath.  This now buried crust varies in strength around the ravines depending on whether or not Monday’s rain event was falling on cold slabs or old surfaces.  This factor determines whether you break right through the crust or stay on top.  The porosity of these old layers had a bearing on facet growth and the current strengths and weaknesses we are dealing.  This leads ultimately to my point that a great deal of spatial variability exists across the mountain.  In some locations today new loading from the south may collapse areas with deep facets under the crust and may not in others.  More probable will be the potential that avalanches in today’s new snow and rain may step down and rip out some locations of this crust.  Although today’s new precipitation is by far the main issue triggering the High danger rating this buried problem is one more factor to consider.

Tonight winds will rage, gusting far in excess of 100mph (160 kph).  This should be able to overwhelm any new encapsulation that occur today to move a variety of crystal types and ice pellets down into avalanche terrain causing new problems for tomorrow.  We’ll have to see exactly how this event plays out today to better assess this subject.   Check back for our Weekend Update later today.

The Lion Head Winter Route is now open. This is a steep route; an ice axe and crampons are highly recommended for safe travel. Please avoid the summer Lion Head Trail due to avalanche risk. The Sherburne Ski Trail should be a reasonable choice this morning but expect it to get heavier and turn into some challenging mash potato-glop later.  Buried obstacles still exist although they are becoming less of an issue.

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 8:10am. 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

2012-01-27 Print Friendly

Avalanche Advisory for Thursday 1-26-2012

This advisory expires at midnight Thursday 1-26-2012

Tuckerman and Huntington Ravines have Low avalanche danger today. Natural and human triggered avalanches are unlikely except in isolated features. The Lobster Claw, the Lower Snowfields, and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when warranted.  Recognize avalanche activity may occur within these areas before forecasts begin.

Conditions haven’t changed too much from 24 hours ago as clear overnight conditions and just a little snow have left the mountain looking pretty much like yesterday.  Over the past 2 nights we have gone through a bit of diurnal recrystalization in our snowpack underneath the surface crust.  Basically a strong temperature gradient in the snow from the rain event, dropping air temperature, and clear skies allowing for good radiation wave movement has “dried out” the snow under the porous crust.  Grabbing this snow quickly it initially feels like dry powder.  Under further examination it’s actually faceted crystals that morphed from the wet rounds they were 2 days ago.  I mention all this because it means that the surface crust likely will not increase in strength, it may possibly get weaker making for difficult off trail movement without floatation.  Snowshoes or skis will make life easier is most places.  Use caution descending steep terrain and be ready for sudden posthole plunges through the crust.  Snow stability-wise we have widespread Low danger with avalanches being unlikely, watch for some very small pockets (what Joe likes to call “pocket lint”) of new snow from yesterday in a few places. 

As I mentioned yesterday ice climbers should anticipate the problem of “ice dams” which usually occur after a mid-winter rain or thaw.  Freezing temperatures begin creating new ice at choke points which puts water flow under increasing pressure looking for a way out.  Often this way out is your ice tool or crampon hole which can unleash an eruption of ice and water.  This phenomenon has blown numerous ice climbers off their stance over the years.  This hazard generally dissipates with time but can be persistent in isolated areas for many days and is unrecognizable beneath the surface.

The big news is another pre-weekend storm is upon us tonight and tomorrow.  5-8” (12.5-20cm) is forecasted for the mountains, but warm air will infiltrate during the event making precipitation more dense and heavier.  Icing and sleet is almost assured in the surrounding valleys possibility making it to the rain form.  We may be spared from some of this pain, but an inverted snowpack with heavy on lighter snow is probable.  Anticipate an increasing avalanche trend late tonight and into daylight tomorrow and cross your fingers for quiet snow on the landscape and not like some kid hucking gravel on a metal roof.   

 The Lion Head Winter Route is now open. This is a steep route; an ice axe and crampons are highly recommended for safe travel. Please avoid the summer Lion Head Trail due to avalanche risk. The Sherburne Ski Trail had decent coverage, but nothing erodes snow faster than a rainy and foggy night. I expect it will be quite icy by the end of the day with numerous exposed rocks.  

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 8:05a.m. January 26, 2012. 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

1-26-2012 Print Friendly

Avalanche Advisory for Wednesday 1-25-2012

This advisory expires at midnight Wednesday 1-25-2012.

Tuckerman and Huntington Ravines have LOW avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features. The Lobster Claw, the Lower Snowfields, and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when warranted.  Recognize avalanche activity may occur within these areas before forecasts begin.

Snowpack lockup is underway as the concrete cures with the dropping temperatures.  All elevations climbed way above freezing yesterday with the exception of the summit which flirted with the 32-33F (0C) mark.  The melt water from warm conditions, in addition to copious amounts of rain, have deeply penetrated our snowpack making isothermal conditions up until the overnight when the mercury fell sharply.  The current “lockup” is occurring from the surface down as liquid free water in the snowpack freezes creating a thickening crust, which in turn is increasing the snowpack strength.  The crust will vary in strength, but expect breakable surface conditions off packed trails and very hard slick conditions on pack surfaces.  As strength increases, angled terrain will get very slick and hard which will make crampons and an ice ax worth their weight in gold!  Skillful use of these tools will be critical in the case of a slip, trip, or fall to keep you from achieving Mach 1 down steep slopes.  The drag co-efficient between ice crusts and modern Gore-Tex isn’t much so be ready to arrest a stumble very quickly with your mountaineering axe.  Use caution descending steep terrain and be ready for sudden deep post hole plunges through the crust.  Ice climbers should anticipate the growing problem of “ice dams” which usually occur after a mid-winter rain or thaw.  Freezing temperatures begin creating new ice at choke points which puts water flow under increasing pressure looking for a way out.  Often this way out is an ice tool or crampon hole which can unleash an eruption of ice and water.  This phenomenon has blown numerous ice climbers off their stance over the years.  This hazard generally dissipates with time but can be persistent in isolated areas for many days and is unrecognizable beneath the surface. 

As the reset button has been hit we have little concern of any old snow instability that was on the ground prior to the rain event due to the “ bridging” effect of the increasing crust thickness.  However a slight attention should be paid to the upslope snow showers that are expected today forecasted to bring us about an inch (2.5cm).  As the mountain moves through today some very isolated instabilities may develop in lee pockets of W and NW winds gusting over 80mph.  As new loading occurs from some new snow today realize is will be loading on top of slick cold crusts which should make for weak bonds at their interface.  

The Lion Head Winter Route is now open. This is a steep route; an ice axe and crampons are highly recommended for safe travel. Please avoid the summer Lion Head Trail due to avalanche risk. The Sherburne Ski Trail will be challenging as it freezes up tight today.  Expect lots of deep frozen ruts and other frozen pleasures to negotiate.  Check your speed frequently and assure your boards have a fresh tune up for edging needs.

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 8:10am. 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

1-25-2012 Print Friendly

Avalanche Advisory for Tuesday 1-24-2012

This advisory expires at midnight Tuesday 1-24-2012.

Tuckerman and Huntington Ravines have Low avalanche danger today. Natural avalanches and human triggered avalanches are unlikely. The Lobster Claw, the Lower Snowfields, and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when warranted; however, you should be aware that avalanche activity may occur within these areas before forecasts begin.

As if this winter hasn’t made us suffer enough, last night the White Mountains region enduring a drenching January rain event. Mt. Washington’s summit received about 0.5” (13mm) of melted precipitation, mostly in the form of freezing rain and rain, while down at Hermit Lake about 0.75” (19mm) of precipitation fell. About the only good thing I can say about this event is that it mostly happened at night. Some of the Hermit Lake precipitation was snow during the daylight hours, but the bulk of the event was rain overnight. As of this morning temperatures have begun to fall. Currently the freezing line is just above the ravines, but as the day progresses this will drop, locking up the mountain in an icy crust.

The end result of this weather pattern will be a very stable snowpack. However, early birds and go-getters should realize that we are at the tail end of a natural avalanche cycle, with a rating of High less than 12 hours ago. As the lockdown takes place the trend is undoubtedly toward stability, but there will be a window of time before everything is absolutely stable. There is currently a lot of moisture in the snowpack. This has had a reasonable amount of time to percolate downward through drainage channels it created within the snowpack. The chances that some of this free water may still reach a cold, dry, weak layer and trigger an avalanche are slim, but they do exist. Similarly, a person may penetrate deeply enough into some sloppy wet snow and hit a weak layer. The best window for this taking place is right now, while ravine temperatures are above freezing or shortly thereafter. On the whole, I don’t believe either of these scenarios presents enough likelihood to warrant more than a Low rating, especially considering the trend toward better stability as the day continues. But remember that Low avalanche danger does not mean the same as no avalanche danger or that there is nothing at all you need to pay attention to. If you want to avoid this potential, just wait a few extra hours for the temperatures to continue to drop.

It seems as though we go through a period like this every winter. One thing that sticks out in my mind after the midwinter thaw is how slick and slippery the steep slopes can become. If you’re planning to be here over the next few days, bring your ice axe and crampons. You’ll need to know how to use them proficiently as well. With the thin snow cover, numerous hazards remain exposed, making a sliding fall a very unwelcome proposition. There’s also a chance for a small amount of snow to fall before tomorrow, which may create stability concerns if it loads onto a smooth ice crust. Stay tuned for more on that tomorrow.

 The Lion Head Winter Route is now open. This is a steep route; an ice axe and crampons are highly recommended for safe travel. Please avoid the summer Lion Head Trail due to avalanche risk. The Sherburne Ski Trail had decent coverage, but nothing erodes snow faster than a rainy and foggy night. I expect it will be quite icy by the end of the day with numerous exposed rocks.

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 8:25am. 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

2012-01-24 Print Friendly

Avalanche Advisory for Monday 1-23-2012

This advisory expires at midnight Monday 1-23-2012.

All forecasted areas of Tuckerman Ravine will have HIGH avalanche danger today.  Natural avalanches are likely and human triggered avalanches are very likely. Travel in avalanche terrain is not recommended.  The Lobster Claw, the Lower Snowfields, and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when warranted; however, you should be aware that avalanche activity may occur within these areas before forecasts begin.

Huntington Ravine will have HIGH and CONSIDERABLE avalanche danger. Yale, Central, Pinnacle, Odell, and South Gullies have High avalanche danger. Natural avalanches are likely and human triggered avalanches are very likely. Travel in avalanche terrain is not recommended. North, Damnation, and the Escape Hatch have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely.

New England winters, how do I love thee? Let me count the ways. I love thee for the sleet, the freezing rain, and the rain… My apologies to poetry fans for the sarcastic paraphrasing, and I apologize to winter enthusiasts for what’s to come later today. The primary concern causing today’s High rating is the incoming precipitation expected to begin after dark. A lovely wintry mix is on its way. It’s a familiar pattern with warm air aloft bringing in precipitation while valley temperatures stay cold a while longer. This event is forecasted to bring about a third of an inch (8mm) of water equivalent in the form of snow, sleet, freezing rain, and rain. Most of this will fall during the evening hours and overnight, which will be the time when peak instabilities are reached.

The mix of precipitation types later today will fall onto some very weak snow layers. Westerly winds deposited these over the weekend after a very light density snowfall on Thursday night and Friday. Soft slabs have developed in the protected lee areas, particularly those with an easterly aspect such as the Sluice, Lip, Center Bowl, and Chute. This weak snow will not take well to sleet and rain landing on it late today, so I expect numerous smaller avalanches to occur in a wide range of locations. Prior to any precip, you can expect conditions similar to yesterday. I would be watchful for unstable slabs that a person might trigger, but naturally triggered avalanche activity won’t be a problem until later. There are a variety of surfaces out there on which to travel. If possible, staying on older surfaces and away from newly deposited soft slab will help you avoid trouble. Most importantly today, do everything you can to get out of avalanche terrain before the precipitation begins.

 The Lion Head Winter Route is now open. This is a steep route; an ice axe and crampons are highly recommended for safe travel. Please avoid the summer Lion Head Trail due to avalanche risk. The Sherburne Ski Trail has decent coverage. Be cautious for some buried landmines and waterbars as they still are problem particularly when you can’t see them.  

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 8:45am. 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

2012-01-23 Print Friendly

Avalanche Advisory for Sunday 1-22-2012

This advisory expires at Midnight Sunday 1-22-2012

Tuckerman Ravine has MODERATE and CONSIDERABLE avalanche danger.  The Lip, Center Bowl, and Chute have Considerable avalanche danger.  Natural avalanches are possible and human triggered avalanches are likely.  Dangerous avalanche conditions exist.  Careful snowpack evaluation, cautious route finding and conservative decision making is essential. Right Gully, the Sluice, Left Gully, and Hillman’s Highway have Moderate avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible.  The Lobster Claw, the Lower Snowfields, and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when conditions warrant.

Huntington Ravine has MODERATE and CONSIDERABLE avalanche danger.  Central gully, Pinnacle, Odell, and South Gully have Considerable avalanche danger.  Natural avalanches are possible and human triggered avalanches are likely.  Dangerous avalanche conditions exist.  Careful snowpack evaluation, cautious route finding and conservative decision making is essential.  North, Damnation, Yale, and the Escape Hatch have Moderate avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible. 

Once again we were teetering on the fence between forecast ratings again today.  Based on the atypical low snow density storm event from Thursday and Friday we have decided to hang on to the Considerable rating for a number of locations that were in the direct lee of West winds.  These winds were the dominate direction for the majority of the loading over the past 72 hours.  Areas that dropped a rating from Considerable you might call “Scary Moderate”. There is a fine line between human triggers being “very possible” (upper end of Moderate) and “likely” (Considerable).  Therefore, recognize that although areas posted at Moderate have more snow stability than the higher rated Considerable locations, many do not linger far behind.  If you decide to go into Moderate posted locales today do not fall asleep at the wheel and give the snowpack a good assessment.  The big factor for all this is the soft slabs that developed over loose unconsolidated low density snow Thursday though Saturday associated with very cold temperatures.  Cold air in place over the region has done little to consolidate or stabilize slabs so the upper snowpack has been sitting in homeostasis.  They have changed very little over the past 2 or 3 days and are waiting for enough time or a slight weather change to stabilize. The other element that could make a change in the snowpack, I.e. fracture and failure, is YOU.  I would be very cautious venturing into soft slabs and choose your routes carefully.  You will find instabilities and slabs vulnerable to human triggers without looking to hard particularly on East facing slopes in the strong lee.  Don’t let the blue bird day suck you into the uncontrollable desire for powder.  Be objective with your analysis and don’t convince yourself everything is fine if you don’t have the data to say that. 

I haven’t said anything about natural avalanche activity potential because it is not too much of a concern.  Dying winds, lack of loading and a slight warm up towards 20F shouldn’t be enough to cause natural slope failures.   But, that will be a different story tomorrow as we move into……. ah yes good ole New England Wintry Mix, aka “mountain slop”, and eventually….rain.  What will freezing rain and rain do to cold soft slabs that have been sitting between -5 and zero degree temperatures you ask?  AVALANCHE!  So the return of natural avalanches issues will likely be the case Monday and Tuesday.  The bright side is this could hit the reset button wiping out instabilities and bridging others making them moot.  More on all that tomorrow.   

We have switched the Lion Head ascent from the Summer Lion Head trail to the Winter route.  The summer trail is not recommended due to the snowfield traverses near treeline and their associated avalanche risk.  Follow the orange signs marking the route at the bottom off the Tuckerman Ravine trail and at treeline where it rejoins the summer trail above the Summer trail avalanche problems.   

 The Sherburne Ski Trail has decent coverage. Be cautious for some buried landmines and waterbars as they still are problem particularly when you can’t see them.    

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 8:45am. 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

2012-01-22 Print Friendly

Avalanche Advisory for Saturday, 1-21-2012

Expires at Midnight Saturday 1-21-2012

Tuckerman and Huntington Ravines have CONSIDERABLE avalanche danger.  Natural avalanches are possible and human triggered avalanches are likely.  Dangerous avalanche conditions exist.  Careful snowpack evaluation, cautious route finding and conservative decision making is essential. The Lobster Claw, the Lower Snowfields, and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when conditions warrant.

Most importantly this morning realize we have just come down from HIGH danger last night and I believe we are at the upper end of the CONSIDERABLE danger rating for all forecast areas.  Maximum winds gusting into the upper sixties and low seventies occurred around dark last night.  This was possibly the period of highest instabilities as denser slabs were being developed in the Ravines from the west winds.  Loading this morning has slowed down substantially which makes the High rating definition of naturals being “likely” a bit over stated.  This makes the Considerable rating  of naturals “possible” more accurate.  However, an additional 1-2” (2.5-5cm) of snow today, with West winds from 30-40+ mph, will keep a threat of natural activity a potential, so be mindful of new loading rates.  The concern that stands out in my mind today is the human triggered avalanche menace.  With cold air hovering around the 0F (-18C) mark today, yesterday’s slabs have not consolidated much at all.  A building wind on Friday created soft slabs over a loose unconsolidated 3.5% snow acting as the weak layer for these new problems to fail on.  Joe and I found unstable snow near treeline yesterday during the late morning and early afternoon.  In locations that didn’t avalanche overnight I would expect a human triggered avalanche to be “likely” in new slabs.  We anticipate continued touchy instabilities across the Ravines until the clouds and new snow subside enough to see what has already avalanched and what didn’t.  A big caution with these instabilities is it’s a Saturday, so plenty of human triggers will be running around perhaps using your ascent as a decent.  Compounding this is the low visibility from clouds and blowing snow.  Some typical descents are Right Gully in Tuckerman and South and the Escape Hatch in Huntington.  Although I can’t recommend being in these locations, based on the instabilities, at all realize that additional risk may be present from above.  Obviously fresh tracks ahead of you should also scream “run away”.  It is a head’s up day!

We have switched the Lion Head ascent from the Summer Lion Head trail to the Winter route yesterday morning.  The summer trail is not recommended due to the snowfield traverses near treeline and their associated avalanche risk.  Follow the orange signs marking the route at the bottom off the Tuckerman Ravine trail and at treeline where it rejoins the summer trail above the Summer trail avalanche problems.   

 The Sherburne Ski Trail has decent coverage at this time with a fresh 6-7” of fluff. Be cautious for some buried landmines and waterbars as they still are problem particularly when you can’t see them.    

 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 8:15am. 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

 2012-01-21 Print Friendly

 

Avalanche Advisory for Friday, 1-20-2012

Expires at Midnight  Friday 1-20-2012

Tuckerman and Huntington Ravines have HIGH avalanche danger.  Natural avalanches are likely and human triggered avalanches are very likely.  Very dangerous avalanche conditions exist and travel in avalanche terrain is not recommended. This includes runout paths of avalanche activity such as the fan in Huntington and the floor of Tuckerman Ravine. The Lobster Claw, the Lower Snowfields, and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when conditions warrant.

The mountain region received a nice unexpected punch of new snow last night vastly exceeding forecasts in numerous areas.  Pinkham Notch, up to the Hermit Lake elevation has received between 6 and 7” (15-18cm) of new snow.  Here at Hermit Lake it’s still snowing with a possibility of 2 more inches (5cm) through the morning. The more significant impact of this new snow is the low densities and moderate wind speeds today.  The snow density average between our manual snowplots is 3.5% which is very light, but not surprising with temperatures below zero F in the higher elevations.  I would expect some steep areas to sluff off due to the new snow’s lack of strength and cohesion.  In “stepped” or “benched” gullies you may see some deep pillows developing.  Some potential examples of this may be found under the ice pitches in Huntington’s Central, Pinnacle, and Odell gullies or across the Tuckerman Headwall in the Center Bowl.  In addition, light to moderate winds from the S last light, moving through the SW, and over to the NW late today will load all primary aspects in the two Ravines.  While this progresses, increasing wind velocities from 25 to 60mph (40-105kph) will develop denser slabs over very loose and unconsolidated snow acting as the weak layer at the interface with the old surface.  Hard and slick surface conditions in the Alpine zone at temperatures around -5F will not hold this cold snow very well.  Therefore today’s winds will have an easy time moving new snow from above treeline down into the avalanche prone slopes of the two Ravines.   Boiling all this down to a simple statement:  I believe delicate, touchy, soft slabs will develop over loose 3.5% density snow today on most aspects from North faces early, progressing rapidly through East faces, and eventually towards the South faces.  I would expect several rounds of natural avalanche activity to occur.  Cold air falling to -10F (-23.5C) tonight at upper elevations will not help consolidate any new soft slabs instabilities that develop today.  I would expect an elevated avalanche danger in at least some areas particularly those that don’t avalanche in the next 24 hours.  Although light, 1-2” (2.5-5cm) of snow forecasted for Saturday could cause a few additional problems.

The Lion Head summer trail becomes an increasing avalanche risk each winter just below treeline, eventually being closed when we open the winter route.  We took a good look at these vulnerable traverses yesterday and they are still peppered with anchors, i.e. brush, trees, and rocks with a limited bed surface.  However this fairly unusual snowfall with very low densities has me believe that a small soft slab or loose sluff is not out of the question.  This is due to the very low strength of any new snow in the deposition minimizing the impact of anchors.  Use caution in this area and use safe avalanche travel practices such as going one at a time.

The Sherburne Ski Trail has decent coverage at this time with a fresh 6-7” of fluff. Be cautious for some buried landmines and waterbars as they still are problem particularly when you can’t see them.   Check out the Weekend Update issued late in the day for any updates and tidbits we can pass along for your weekend trip planning.

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 8:40am. 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

2012-01-20 Print Friendly

Avalanche Advisory Thursday 1-19-2012

Expires 12:00 midnight, January 19, 2012

Tuckerman and Huntington Ravines have LOW avalanche danger.  Natural and human triggered avalanches are unlikely EXCEPT IN ISOLATED TERRAIN FEATURES. The Lobster Claw, the Lower Snowfields, and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when conditions warrant.

The mountains are basking in the sun’s glory this morning albeit a rather chilly start at dawn.  Temperatures overnight inverted as winds died down and the cold air aloft dropped into the valleys.  By the time daylight rolled around the base of the mountain was colder than the summit with a temperature of -5F (-20.5C) at Pinkham Notch.  If you have the right gear for being in the mountains with cold air today you will be treated by copious sun, beautiful vistas and low wind speeds from the SSW at 10 to 25 mph (16-40kph).

Very high winds over the past 2 days have done the job scouring the mountain of available snow and packing it into the nooks and crannies where protected from the wind.  This wind was associated with some upslope snow showers that generated under an inch of snow.  Generally speaking we have widespread hard scoured slopes in the two ravines and numerous locations showing crust.  An interesting snowpack development to watch for is some intense faceting under the most recent crust.  Facets will continue to grow with today’s cold clear air.  I would expect crusts to erode and lose strength as they become cannibalized by new crystal growth.   This will be something to consider during the next loading event.  A few locations have some new snow in the strong lee particularly in Tuckerman Ravine from the Sluice over to the Chute.  If you were hunting for avalanches and spent the day trouncing all over the Ravine you would likely find an unstable pocket or two, but generally these are easy to avoid by paying attention and sticking to hard old surfaces.

Later today winds will be on the increase, building to 25-40mph (40-65kph) with clouds moving into the region.  Snow will begin very late in the day, forecasted to accumulate by Friday morning in the 2-4” (5-10cm) range on winds from the S shifting to the WNW.  Escalating speeds overnight will load new slabs into both ravines overnight if the forecast plays out.  Expect an increasing avalanche danger overnight with elevated ratings beyond today’s Low danger advisory.  This will all transpire during the presence of cold air in the zero to -5F (-18 to -21C) range which will likely produce both low density snow and slabs that will retain their instability into the weekend.  Stay tuned and check tomorrow’s avalanche advisory.  

 The Sherburne Ski Trail has decent coverage at this time. You don’t need to work too hard to avoid exposed rocks, but you may see a couple. In addition, the breakable crust is a bit arduous under ski so expect some challenging conditions until more snow comes in.

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.

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

2012-01-19 Print Friendly

Avalanche Advisory for Wednesday 1-18-2012

This advisory expires tonight at midnight.

Tuckerman Ravine has Moderate and Low avalanche danger. The Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Right Gully, Left Gully, and Hillman’s Highway have Low avalanche danger. Natural and human triggered avalanches are unlikely. The Lobster Claw, the Lower Snowfields, and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when conditions warrant.

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

There are some stability concerns to be thinking about today, but you might have a challenging time getting to them. Winds today will be gusting from the W to speeds over 100mph (160kph) for most of the day. This will make travel into either ravine difficult enough, but to up the ante, temperatures will fall throughout the day reaching around -5F (-21C) at the summit. Much of the avalanche terrain in the Cutler River Drainage is scoured down to stable snow, thanks to sustained overnight winds peaking at 129mph (209kph). The areas posted at Low danger today are those where this has happened. The exception to this is Right Gully. There is a general lack of snow in the gully, except one large patch on the climbers left side just above the mouth of the gully. Here, the Low rating is more due to this being an isolated pocket within the forecast area than due to scouring.

The locations posted at Moderate today have been the most protected from the strong winds. Last night about an inch of frozen precipitation fell on the mountain while light upslope snow is currently falling. The combination of new snow and the strong winds transporting snow from elsewhere on the mountain is creating a loading situation. I expect any new slabs that will develop in the early hours of today to be dense and strong. It’s often difficult for a person’s impact on a hard slab to be enough to initiate a fracture and failure of the slope, but remember that snow stability is a balance of strength versus stress. When a slope is actively loading it is nearly impossible to accurately assess how this balance is playing out. If avalanche activity occurs today, it would not surprise me if it were naturally triggered from new loading this morning. Saying this, I don’t believe this hazard warrants a greater rating than Moderate. When wind loading comes to a close and skies clear out, it also would not be too much of a surprise to find generally good stability in many of the Moderate rated areas.

 The Sherburne Ski Trail has decent coverage at this time. You don’t need to work too hard to avoid exposed rocks, but you may see a couple. A light amount of new snow under a thin breakable crust will keep your edges on the old surface.  January 20th looks to be the turning point this winter—if not for the winter at least there may be some fresh snow for the weekend. Let’s hope for the best with this one.

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 8:250am. 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

2012-01-18 Print Friendly