Avalanche Advisory for Wednesday, 3-07-2012

This Advisory expires at midnight, Wednesday 3-07-2012

Tuckerman Ravine has Considerable and Moderate avalanche danger. The Lobsterclaw, Right Gully, Sluice, Lip, Center Bowl, Chute, and Left Gully have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. 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 Moderate and Low avalanche danger. Central, Pinnacle, Odell, South, and the Escape Hatch have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. All other forecast areas have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features.

Today is a full on avalanche brain teaser with a number of factors for the avalanche enthusiast to consider.  Three dominant issues and their exact timing are the important parameters that have generated today’s avalanche forecast.  Since the weekend, the upper mountain picked up about 7” of very low density snow with low to moderate wind speeds ever since.  Yesterday’s peak wind of 65 from the NW did a fairly respectable job pushing around most of this alpine snow, but today winds are expected to ramp up, possibly hitting the century mark this afternoon.  This will augment the current snow plumes already at the ridge potentially causing some new loading concerns.  While this occurs, continued warm air will be escorted by the high winds causing the first substantial warmup for the cold snowpack in a while.  Although we did see a little bit of solar gain yesterday, today’s warm up will be more significant.  There is a strong likelihood for avalanche terrain to remain above freezing overnight before increasing in temperature even more on Thursday with a chance of rain.  The summit is expecting the mercury to be in the mid thirties F today, while here at Hermit Lake it is currently just shy of 40 degrees already.  There will be a battle between increasing temperatures and wind speeds today.  As winds continue to pick up they will help keep many snow slopes cool even as the ambient air gets warmer.  So the exact timing of each of these and how they affect one another is the key factor to observe today.  A number of strong lee areas from W winds, with a SE and S aspect component, will warm the most today in the direct sunlight.  I have an nagging concern about these areas and the potential natural slope failure as the tensile strength of cold slabs get baked out over some under riding facets and unconsolidated snow weaknesses below. 

So we have both some new cold slab issues due to loading snow with increasing winds and then some intense warming mostly on protected southern aspects.   Ultimately I believe there is a good chance new snow loading, high winds, and increasing wind issues will balance each other out coming to a reasonable equilibrium.  However, I cannot ignore that these factors may escalate enough to possibly cause a natural avalanche hence the “Considerable” avalanche danger rating for a number of our largest snowfields and particularly those facing S.  In Huntington these S faces are posted at “Low” due to their overall thin ribbon like nature and how high W winds rip these narrow gullies more readily than in Tuckerman.  This should keep the majority of S faces cool enough to limit the concern.  

Tomorrow, slopes may still be above freezing at dawn with the chance of rain.  This may continue to escalate the avalanche danger so be prepared for continued natural avalanche problems with a higher magnitude than today.

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 8:40a.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

2012-03-07 Print Version

 

Avalanche Advisory for Tuesday, 3-6-2012

This advisory expires at midnight, Tuesday 3-6-2012.

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

Huntington Ravine has Moderate and Low avalanche danger. Central and Pinnacle gullies have Moderate avalanche danger. Natural avalanches are unlikely; human triggered avalanches are possible. All other forecast areas have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features.

It’s pretty amazing what a small amount of moisture in the atmosphere can accomplish. Two nights ago, an unexpected upslope snow event took place, laying down about 7” of very light density snow across the higher terrain. This has since been subjected to W to NW winds blowing 35-50+mph (56-80kph), which has moved a lot of snow into Tuckerman Ravine. Across the upper rim of the ravine, the winds have scoured away the new snow, pushing it into stronger lee areas such as below the Lip, below the ice in the Center Bowl, and above the narrows of Left Gully. Other locations have also accumulated a significant amount of snow; the areas mentioned are just some of the most notable ones. This morning, skies are clear and temperatures cold. The NW 50mph (80kph) winds are currently at the upper end of what they were forecasted to be, and due to the winds there is a consistent ground blizzard bringing additional snow into Tuckerman. Today’s Considerable ratings are in large part due to the threat of naturally-triggered avalanches, but we are also thinking about how it would be likely for a person to trigger an avalanche in these newly developed slabs. In addition to the most recent snow, field work over the weekend gave us some concerns about underlying stability in the 12” snowfall from last Thursday. Recent weather has been preventing that dry, light snow from stabilizing in many areas.

Huntington Ravine was affected differently by the new snow. The northern gullies (North, Damnation, and Yale) were mostly scoured down. This is unusual with wind speeds being on the lighter side, but with such light density snow, it is not unreasonable. Central and Pinnacle were obscured by constant plumes of blowing snow. We suspect less scouring took place here than the northern gullies, but the airborne snow prevented us from confirming this. Odell, South, and Escape each have some localized areas of concern, but these are small enough to be considered “isolated terrain features.” If you pay attention in there, you can stick to areas with old surface or a thin veneer of new snow on top of the old surface. However, in the isolated areas you may find unstable new slabs that can avalanche underfoot as well as hard wind slabs that are thin enough to crack and avalanche.

Solar energy today might be a double-edged sword. One the one hand, it can help snow become more stable, if the energy it provides is strong yet gentle. On the other hand, if it’s too strong and not gentle enough, the stability trend can quickly stop and the snow can rapidly become unstable. Southerly-facing slopes will receive the most solar gain, while E and N facing slopes won’t be affected much. The next couple days are looking pretty warm, with temperatures heading above freezing all the way to the summit. Our field work today will be focused on how this might impact stability in the next couple days.

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.  
  • 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

2012-03-06 Print Friendly

Avalanche Advisory for Monday, 3-5-2012

This advisory expires at midnight, Monday 3-5-2012.

All forecast areas of Tuckerman and Huntington Ravines have Considerable avalanche danger today. Natural avalanches are possible; human triggered avalanches are likely. The only exception to this rating is the Little Headwall, which has Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features.

I guess it’s true what they say about weather being unpredictable at times on Mt. Washington. In the most recent instance, it worked in favor of those who want more snow, but against those who were looking to recreate in avalanche terrain today. Over the last 30 hours, the summit has recorded 6.5” (16.5cm) of new snow. Yes, that’s correct, six and one-half inches. Not only is the total depth remarkable and unexpected, but the density is incredibly light, coming in around 2%. If we hadn’t seen these flakes with our own eyes, we wouldn’t believe the accuracy of the measurement. But they were practically floating in the air like little helium balloons, so I’m a believer. Most of this snow fell between noon and midnight; winds during this time started very light and increased to their current speeds of around 40mph (65kph) from the WNW. A small amount of additional snow is expected to fall this morning.

Today’s stability concerns are primarily related to the new light density snow. It doesn’t require a strong wind to move this snow from one location to another (e.g. from the Alpine Garden into Central Gully). New soft slabs are being created and are growing as I type this advisory. Despite the trend for skies clearing today with high pressure, winds will continue to pick up and deposit the recent snow into steep slopes of both ravines, even after skies clear later today. Direct loading and cross-loading will be taking place in all forecast areas. Expect new slabs to be soft and very reactive to triggering, either from a person or from the increasing load of wind-transported snow. I want to emphasize that today’s Considerable rating is for both human triggered avalanches being likely as well as the possibility of natural avalanches.

The threat of avalanches today is real, and presents additional concerns. We are also thinking about the chances of an avalanche stepping down into slabs that existed prior to the new snow. Field work yesterday showed a spatially-variable snowpack, with some locations registering some frighteningly easy test results while other areas showed reasonably good stability at the surface. We can foresee an avalanche that does step down into older instabilities being quite large, and that conclusion was drawn even before we knew there would be another 6.5+” of snow about to be loaded onto the slopes. Overall, this is a complex snowpack that will require focused attention to navigate safely. To conclude, I recommend avoiding avalanche terrain until visibility improves, and then you’ll need to give some serious consideration to your objectives for the day. There are always options that don’t involve avalanche terrain.

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.

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

2012-03-05 Print Friendly

Avalanche Advisory for Sunday, 3-4-2012

This advisory expires at midnight, Saturday 3-03-2012. 

All forecast areas of Tuckerman Ravine have Considerable avalanche danger today. Natural avalanches are possible; human triggered avalanches are likely. Two exceptions to this rating: the Lower Snowfields have Moderate avalanche danger, natural avalanches are unlikely and human triggered avalanches are possible, and the Little Headwall, which has Low avalanche danger.

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

We’ve got a fairly complex set of variables to wrestle with this morning, including recent weather history, avalanche activity, and forecasted weather, so bear with me as I do my best to distill these down into something useful. What we’re dealing with for snow stability is the aftermath of Thursday’s heavy snowstorm. In case you missed it, we received over a foot of light density snow while winds were out of the SE and E. Winds have since shifted back and forth from the W to the S and are currently from the W again. Summit wind speeds last night got very strong, gusting to 99mph (160kph), but we are suspicious that the strongest winds stayed aloft and did not push very far below the summit. The lack of wind-scouring in places such as Hillman’s is an important clue toward this suspicion. In Huntington the upper reaches of the gullies received some scouring, but the middle and lower sections were more loaded than we’d expect after this weather pattern. Meanwhile yesterday, the mountain warmed up and some freezing drizzle created a thin crust everywhere except underneath tree cover. Although it received some freezing rain or drizzle, the uppermost elevations of Mt. Washington did stay below freezing. The avalanche activity we can observe this morning is also less than we would have expected with yesterdays weather, and it’s difficult to determine when exactly these took place. I’m confident enough to say that numerous avalanches have happened in several areas since Friday night, when winds started to pick up.

So starting out today, we’ve got numerous forecast areas that are preloaded with fresh new slab. Based on recent activity, it’s a safe assumption to say these newly developed slabs have some existing instability problems. Currently, many places are in the upper end of the Moderate rating, such as midsections of Odell and South in Huntington and the Sluice, Lip, and Hillman’s in Tuckerman. Today’s weather forecast calls for a chance of additional snow, though only a trace to 2” (5cm) is expected and most of this will come in the afternoon as a weak cold front passes by. Winds will be from the W and decreasing in velocity, but I would expect the speeds to be sufficient to deposit any new snow onto the already loaded slopes. This will drive the avalanche hazard from the upper end of Moderate solidly into the realm of Considerable. Not only will naturally-triggered avalanches be possible, but the likelihood of a person triggering a slide will be elevated as well. If new snow accumulations don’t materialize, actual avalanche hazard in the Considerable rated locations will continue hover between Moderate and Considerable. If the upslope snow guns start up earlier and heavier than expected, then the trend will be toward increasingly unstable snow.

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 8:45a.m. 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

2012-03-04 Print Friendly

Avalanche Advisory for Saturday, 3-03-2012

This advisory expires at midnight, Saturday 3-03-2012

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 on a variety of slope aspects and angles.  Travel in avalanche terrain is not recommended, including run-out paths.  The only exception to this is the Little Headwall which has Moderate avalanche danger.

The old adage, “you don’t know where you’re going if you don’t know where you’ve been” is a perfect sentiment to capture our developing avalanche situation today. Let’s back up a couple of days.  On Thursday our most recent storm hit the mountains, dumping about 12” (30cm) on the Presidential Range.  Overall snow densities where light, averaging about 7% with the last 4” (10cm) being around 4%.  During and since that snowfall, winds have been quite light for Mount Washington, averaging about 28-29mph with brief gusts over 45mph on Thursday.  Through most of Friday, summit winds hovered around the 20 mph mark. Down at the horizon of the Ravines, at approximately the 5000ft level, wind speeds were less, leaving our new fluffy blanket fairly unaffected except in the more exposed locations. Then at midnight, several hours ago, snow began falling again with an increasing wind.  By 3:30am, Washington’s summit was averaging about 60mph, gusting to 74mph, from the South.  After relative calm period, I can almost hear it yelling, “hey guy’s I’m back, what’ya been doing?!”  Winds today are forecasted to shift, walking clockwise from the current S towards the W.  As winds shift to our prevailing directing and continue to build speed, our east-facing Ravines will get overwhelmed with the left over storm snow lying in the alpine zone.  This is particularly true in Tuckerman due to Bigelow lawn, a flat plateau the size of 600 football fields.  This area sits above the Ravine right in line for winds with a westerly component, providing an incredible supply of snow to be moved.  I would expect more than one avalanche cycle out of this event as slopes get reloaded, cocked to fire, and the trigger pulled by the final flake and gravity tugging on steep slopes.  The light densities will also make cross loading of S-facing areas easier than usual.  Although these slopes will not harbor the dangers of N and E aspects today they will still likely produce natural avalanches.  In areas such as Damnation and North, avalanche activity may be limited to smaller slabs and sluffs, but these can still easily knock you off a stance. To add to this entire situation, new snow has been falling over the last 4 hours and is expected to continue through the day, perhaps changing forms into a bit of a “precipitation grab bag”.  The summits forecast is for 2-4″ (5-10cm) of snow, sleet, and freezing rain, maybe even followed by rain. As these heavy forms of precip fall, any pre-existing instabilities will rapidly become worse.

All of this history and current weather translates quickly and definitively into today’s rating of “HIGH”.  All of our forecasted slide paths have fully developed tracks so you can expect full avalanche runouts to occur.  Although the light density snow can be easily picked up for transport today, crystals will be pulverized into small grains as winds increase, making for denser slabs packed in the deposition.  This increased mass may push some avalanches full path, criss-crossing the floor and approach fans of both ravines.  Travel in avalanche terrain, which includes run-out paths, is not recommended.  As blowing snow and clouds will offer very limited visibility, going into the Ravines just to look won’t give you much more than placing yourself as lead pin in the bowling alley.

The warmth that is expected today won’t last too long. Probably just long enough to make a mess of the nice snow at lower elevations, such as on the Sherburne Ski Trail where the lower sections are currently getting a freezing rain coating. Overnight, mountain winds will start to crank up, perhaps blowing over 100mph for a short time, then decreasing again into good wind-loading velocities. Tomorrow’s avalanche danger will depend in large part on avalanche activity today, more snowfall overnight and tomorrow, and whether or not the overnight winds were able pummel any gullies into full submission.

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. 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

2012-03-03 Print Friendly

Avalanche Advisory for Friday, 3-02-2012

This advisory expires at midnight, Friday 3-02-2012

 Tuckerman and Huntington Ravines have CONSIDERABLE avalanche danger.  Natural avalanches are possible and human triggered avalanches are likely.  Dangerous avalanche conditions exist therefore careful snowpack evaluation, cautious route finding and conservative route finding is essential.  The only exception to this is the Little Headwall which has Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features.

  Averaging our Harvard and Hermit Lake manual snow plots we picked up about 12” (30cm) of new snow from this storm.  We saw the evidence of multiple avalanches particularly in Huntington due in part to the gullies being a bit steeper in places and more water-ice present.  Sluffs occurring off of steep slopes and blue ice was the likely trigger for numerous very soft slab releases.  Our ridge top field time yesterday proved that our assumptions were correct, and we encountered very delicate soft slabs with little strength.  Storm snow densities averaged about 7%, however as the storm progressed densities decreased with the top 4” (10cm) only coming in at 4%.  This is important not only because it’s champagne powder under ski, but because it will be very easy to move with an increasing wind.  Summit winds are forecasted to escalate and shift from the current direction of W at 20mph to SW and 35mph later.  Only slight ridge top winds will be needed to move this low density snow down into the upper start zones to once again create delicate soft slabs loaded on loose unconsolidated snow.  This will increase the possibility of natural avalanche activity which has forced us to the “Considerable” rating decision.  A number of locations are currently at the upper end of the Moderate rating, but this should change through the day.  So the big bulls-eye factor to watch today is wind speed and EXACTLY what speeds they increase to.  If you notice any snow transport going on, even low ground level drifting; expect very touchy slabs to be developing. 

The other big news that I have been referring to over the past couple of days is the ramping up of wind velocities tonight and over the weekend.  Tonight winds will continue shifting to come from the S and increase to 60+mph (96kph) with more snow.  This is by far the highest speeds we have seen since the recent storm began.  These winds will whip up the blanket of alpine zone snow and pour it into avalanche terrain over a weak loose snow layer.  Then tomorrow, winds will shift back to the W and approach raging levels at 80 perhaps gusting to 100mph with more snow!  It is quite plausible the upper elevations will remain all snow from the precipitation tonight and tomorrow, with enough water equivalent to give up over 6” (15cm) of the white stuff.  I would anticipate “High” danger ratings for numerous locations on Saturday.  Check in to our “Weekend Update” later today for updates on this developing situation.

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 8:45a.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

2012-03-02 Print Version

 

Avalanche Advisory for Thursday, 3-01-2012

This advisory expires at midnight, Thursday 3-01-2012 

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 the full runout paths for all slide paths.  The only exception to this is the Little Headwall which has Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.

 A WINTER STORM WARNING is in effect until 9pm tonight.  Anticipated snowfall totals have slowly been ratcheting up over the past two days with current expectations of 5” (12.5cm) in the far north being likely and areas in the southern part of the State getting upwards of 15” (37.5cm).  Here in the White Mountains we will fall somewhere in between with 8-12” (20-30cm), with the higher elevations leaning towards the upper end of this forecast.  With 3 (8cm) of low density inches on the ground already we will continue to see snow all day and into the evening. This long duration event should deliver precipitation at a steady rate, producing another 5+/- inches (12.5cm) today and an additional 3-5” (7.5-12.5cm) tonight.  This will be brought to our terrain on SE winds peaking around 40mph before decreasing later today.  This will predominately load slopes and gullies with a northern facing component such as the start zones of Hillman’s Highway, Left gully, the Escape Hatch, South Gully, and Odell.  Cross loading of the Chute, Center Bowl, Pinnacle, and Central is also likely.  

Reaching the “High” danger rating should take most of the day with the majority of areas in the “Considerable “ range until this afternoon.  The aforementioned north to east faces will reach “High” first with south facing slopes like Right gully struggling to meet the “High” rating by dark.  A substantial factor in today’s stability assessment is the fairly light densities this morning at around 6%.  This will load into a soft slab that will have intact crystals due to the light winds and cold temperatures.  These slabs should be sensitive to triggers and be fairly weak, overall.  Even the slopes that are pointing into the wind should see sluffing in steep terrain and natural soft slab releases late in the day.  Expect sluffing to entrain loose snow and trigger very soft slabs on numerous aspects.  The later we get into the day the more I would avoid the concept of “just going into the Ravines to take a look.”  Expect the run out of a number of avalanche paths to criss-cross your intended route.  For example, once you pass the “Connection First Aid Cache” on the way into Tuckerman you will be in the run out of Left gully.

Winds are expected to wrap tonight through the W to the NW and then return to the SW tomorrow.  Velocities should stay light in the 30mph range on the summits continuing the formation of delicate soft slabs near the horizon of most start zones.  Wind speeds will pick up substantially over the weekend from our prevailing W and NW causing a new round of avalanche problems.    On a very upbeat note I would expect the Sherburne Ski trail to be pretty delightful over the next 2 days. This is a great way to kick off March, isn’t?

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

2012-03-01 Print Version

 

 

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

 

Avalanche Advisory for Monday, 2-27-2012

This advisory expires at 12:00 midnight Monday, February 27, 2012

Tuckerman Ravine has MODERATE and Low avalanche danger. Right Gully, the Sluice, the Lip, the Center Bowl, and the Chute have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. All other forecast areas have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features.

All forecast areas of Huntington Ravine have LOW avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features.

Remember this past weekend? Those were good times, eh? After all the fun, today certainly feels like a Monday morning. The excitement of a good snowstorm has passed, avalanche danger has subsided quite a bit, and the threat of clouds lowering is putting a gray feeling on the day. But if you’re a snow junkie, take comfort in the 1-3” (2.5-7.5cm) that are forecasted to fall later this afternoon and tonight. This snow is worth paying attention to, particularly if you’re going to be out on the mountain after dark, but I don’t think it will start early enough to affect stability today. Current conditions will remain for the daylight hours. Anticipate rising avalanche danger after snowfall begins to accumulate.

Yesterday, we were able to get into both ravines for a look at the aftermath of the weekend avalanche cycle. Huntington had slides in Pinnacle, Odell, and South. Much of the terrain in Huntington at this time is either old surface, bed surface, or wind-hammered snow, hence the Low rating. The strong winds that took place throughout much of the storm didn’t let a lot of snow stick to the gullies. The northern gullies have very little snow left in their upper sections.

In Tuckerman, slides were noted in Hillman’s, Duchess, Left Gully, Center Bowl, the Lip, and Right Gully. The one prominent location that appears to have not slid is the Sluice. Interestingly, the surface texture in much of the Sluice is almost identical to what you’ll see above the crown lines in the Bowl and Lip. I would treat this area with a healthy dose of caution. There are many bushes that were recently buried here, which often act as weak points in the slab. Judging from the thick debris in the floor from the Lip and considering that the runout is an enormous pile of boulders (i.e. Lunch Rocks), an avalanche in the Sluice would be a tough one to walk away from. The crown line(s) in the Lip and Center Bowl have reloaded to some extent. In these areas the Moderate rating is based on hangfire as well as the new loading on the old bed surface. In the aftermath of these avalanches, spatial variability takes on a whole new meaning. In Right Gully and the Chute, there is a mix of wind scouring and wind loaded areas. Climbers may find it easy enough to avoid the areas of greatest instability, but the lack of good snow in stable locations might cause a skier and snowboarder to gravitate toward the unstable snow. Finally, in Hillman’s, as well as the other areas rated at Low, expect isolated pockets of unstable snow. Hillman’s has a lot of old surface exposed, but also has numerous patches of newer slab on top of it. Left Gully was hammered by the winds and has good stability. And, the entrance into the Little Headwall is finally filling in with a reasonable amount of snow. There are still open water holes and some that were just recently covered, so use caution in this area. After this morning’s trip into Tuckerman I’ll try to post some pictures onto our website to show you what all this looks like.

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 8:55am. 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

2012-02-27 Print Friendly