Avalanche Advisory for Tuckerman and Huntington Ravines

Posted 8:30a.m., Tuesday, February 08, 2011

Tuckerman and Huntington Ravines will have Considerable avalanche danger today.  Natural avalanches are possible and human triggered avalanches are likely.  The only exception to this rating is the Little Headwall in Tuckerman Ravine which has Low avalanche danger.  Natural and human triggered avalanches are unlikely in this forecast area. 

Active weather continues to keep us on our toes up here on Mt. Washington.  Today’s weather will bring snow, dropping temperatures and increasing winds which will work together to create new avalanche issues in the Ravines.  The extent of these issues will depend on how much snow accumulates on the mountain today.  The Mt. Washington Observatory is forecasting for 1-3” (2.5 to 7.6 cm) of snow today with another trace to 2” (5 cm) overnight.  This seems to be playing out but I can’t ignore the National Weather Service’s forecast that is calling for up to 6” (15 cm) of new snow today in higher terrain.  What snow does fall will be accompanied by winds out of the NW that will be increasing to 70 to 90 mph (112 to 144 kph) with higher gusts.  These winds will transport new snow into the ravines creating wind slab that will increase in density as the day progresses.  The increasing slab density will occur as winds ramp up, blast snow crystals apart and pack them into cohesive layers (wind slabs) in lee areas of NW winds.  Today’s winds will exceed velocities the mountain has seen since our most recent storm on Saturday night and Sunday.  These winds could find snow that is lingering from this last event to transport into the Ravines, adding to today’s snow stability issues.  If we max out the forecasted snow totals, reaching 6”, I expect there will be numerous areas that will have natural avalanches.  If we stay on the lower end of the forecasted snow totals, some locations will struggle to reach the Considerable rating today.  Aside from what is going to change today, most areas in Tuckerman Ravine currently have wind slabs that fall within the Moderate rating.  Justin and I spent time in the field yesterday evaluating the aftermath of Sunday’s avalanche cycle.  At least four gullies avalanched in Huntington.  In Tuckerman, Hillman’s Highway ran pretty big and the Bowl took the prize with a large avalanche that fractured from the Chute to the Lip.  It is worth noting that no significant activity was observed in many of the other forecast areas in Tuckerman and they are pretty loaded up with wind slab.  Some of these could get ripped out if we start having natural avalanches today.

Cold weather is working its way into the mountains with temperatures expected to drop to -20 F (-29 C) over night with winds exceeding 100 mph (160 kph).  Tomorrow temperatures are forecasted to top out at -10 F (-23 C) and westerly winds will still be cranking between 65 and 85 mph (105 and 137 kph) making for prime ice cream headache conditions.  Take this challenging winter weather into account when planning tomorrow’s outing.

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. This advisory expires at midnight. A new advisory will be issued tomorrow.

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

Printable Advisory

Avalanche Advisory for Tuckerman and Huntington Ravines

Posted 8:33a.m., Monday, February 07, 2011

Tuckerman Ravine has MODERATE avalanche danger today.  Natural avalanches are unlikely and human-triggered avalanches are possible. The only exception to this rating is the Little Headwall which has LOW avalanche danger. 

Huntington Ravine has LOW avalanche danger.  Natural and human-triggered avalanches are unlikely.

While the summit is still in the fog this morning we’ve cleared enough to see how the mountain has changed following Saturday’s storm.  High winds early in the day yesterday were able to strip much of the new snow out of the gullies in Huntington hence the Low rating.  Pockets of windslab do exist in Huntington but they are isolated in nature and exist mainly in areas that were well sheltered from strong W and NW winds. Examples include the middle of Yale, below the ice in Central and the climber’s right side of the start zone for South Gully.  Tuckerman is a very different story with little scouring and sculpting evident except for the upper reaches of Hillman’s and Left Gully.  Evidence of avalanche activity can be picked out in many areas though additional loading has obscured many of the signs.  As an example one can easily connect numerous pieces of a partially buried crown line across the Center Bowl and through the narrows of the Lip.  This fracture is evidence of at least the second large avalanche in that forecast area this weekend, the first occurring Saturday morning shortly before 9 a.m..  The Observatory recorded blowing snow in their hourly observations up until about 9p.m. last night when winds dropped blow 45mph (72kph) and transport ended. Forecasted winds will stay below this threshold for the most part today with the occasional higher gust.  A trace to 2” (5cm) of new snow is forecasted for later today but I don’t believe that it will play in as a major factor in today’s stability. More snow is expected to fall tonight and into tomorrow though it looks like it may only total a few inches.  I would expect elevated avalanche danger tomorrow especially if the storm tracks closer to our area and we pick up more significant accumulation. Brian and I will be spending time in the field today trying to get a handle on where avalanche activity occurred, how the different slide paths have changed, and what role if any Saturday’s crust is playing in stability.

The John Sherburne Ski Trail has good coverage following the recent storms but the thundercrust from Saturday night’s wild weather makes for some tough turns.  A handful of hearty souls made the most of it yesterday and acted like the Coast Guard cutters breaking up the frozen sea.  It will only get better with each pass so do your public service and take a second lap!

 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.
  • This advisory expires at midnight. A new advisory will be issued tomorrow.

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

Printable Advisory

Avalanche Advisory for Tuckerman and Huntington Ravines

Posted 8:23a.m., Sunday, February 06, 2011

Tuckerman and Huntington Ravines have HIGH avalanche danger today. Natural avalanches are likely and human-triggered are very likely.  Travel in avalanche terrain is not recommended.  The only exception to this rating is the Little Headwall which has Moderate avalanche danger. 

What an exciting 24 hours it’s been!  Yesterday morning we started the day with a large natural avalanche in the Center Bowl.  The failure of the slab was not that surprising but it serves as a good reminder of how a seemingly small amount of wind-loading can tip the scale even under bluebird skies.  Clouds settled in by mid afternoon and by the time we left the mountain blizzard-like conditions had engulfed the area.  Snow came in with a vengeance, making all the snow lovers giddy with excitement.  Unfortunately snow gave way to mixed precipitation before midnight and a crust began to form at most elevations. This crust was soon buried as the amazing and elusive thundersnow poured out of the storming skies. By daybreak winds had made the swing to the NW and ramped up to 80+mph (129+kph).  The summit picked up just under 10” (25cm) while we got a few inches less at Hermit Lake.  Right now at Hermit Lake it’s 15F (-9C) and the wind is sending snow and ice pellets whipping through the air.  Winds are forecasted to back off a little later in the day but for now there is significant wind-loading occurring in both ravines.  At Hermit Lake the crust is about .1” (6mm) thick and buried 2.5” (6cm) down from the surface where wind hasn’t either torn it apart or buried it deeper.  It is unclear how the crust developed in the start zones but we do know that the summit received their share of thunder-driven ice pellets last night.  Although the average snow densities are skewed by these pellets and the other forms of mixed precipitation that fell, the snow above and below the junk is actually of an average density.  Another trace to 2” (5cm) may fall over the course of the day today and add to what’s available for transport.  We expect that when the clouds lift we’ll see evidence of an impressive avalanche cycle. Most paths were finally reaching maturity before this storm and a few have made some impressive runs.  This storm will likely extend their debris fields even farther so I’d advise against trying to “just go close enough to have a look.”  With today’s visibility that means getting yourself into a run-out and risking a burial.

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.
  • This advisory expires at midnight. A new advisory will be issued tomorrow.

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

Printable Advisory

Avalanche Advisory for Tuckerman and Huntington Ravines

Posted 9:15 a.m., Saturday February 5th 2011

Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger.  The Lip, Chute, and Hillman’s Highway have Considerable avalanche danger.  Natural avalanches are possible and human triggered avalanches are likely.  All other forecast areas have Moderate avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible.  Expect heightened avalanche conditions on specific terrain features.  Evaluate snow and terrain carefully. Anticipate the potential for large avalanches in isolated areas. The only exception to this rating is the Little Headwall which is Low.

Huntington Ravine has MODERATE and LOW avalanche danger.  Central, Pinnacle, Odell, and South have Moderate avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible. All other forecast areas have Low avalanche danger.  Watch for isolated pockets of instability in these areas.

It’s been an interesting couple of days since Wednesday’s storm with a lot of avalanche activity, some locations sliding repeatedly.  Most notably are Hillman’s Highway and Dodge’s Drop which ran again yesterday morning due to high winds reaching 65-75 mph (105-121kph) and the main Tuckerman Center Bowl that avalanched this morning between 8:45 and 9:00am.  Plumes of snow have been the norm now for over 24 hours as some loading continues up high in several start zones.  In general new loading should remain light across the mountain though a few locations of note will be easy to pick out this morning as blowing snow swirls over the ridge.  Since yesterday some strong lee areas have continued to grow, most notably in the Tuckerman Lip and under the Headwall ice.  Obviously under the Headwall ice these slabs became overwelmed this morning with a large natural avalanche propagating very well in new hardslab.   This is a substanial piece of information and should be the main driver for decisions today.  Natural avalanche activity is a clear indication that unstable slabs exist. Taking these facts as well as my field experiences yesterday with settlement cracks in hard slab, I believe in areas posted at Moderate we are on the absolute upper end of the ratings defintion particularly in Tuckerman.  I would have the most conern about the hang fire above the new avalanche in the Center Bowl and everything from the Chute to just past the Lip.  

The main issue we are dealing with is a layer of weak low density unconsolidated snow that fell during a period of very low wind following the main storm.  Because of this I have some concern that if slabs fail under new load, like you, they could propagate into a sizable avalanche.  In some locations where hard slabs are thick I believe they have bridged over the weak layer of unconsolidated snow, but as you move to the thinner edges it may become easier for your weight to impact these weaknesses.  So pay attention to the variability out there as it is a heads up day and remember a few key points.  New loading has been occurring over the past 24 hours; natural avalanche activity has occurred during this same timeframe; hard slabs have formed over 6% snow that fell at the end of Wednesday’s storm; and it has remained cold over the past 72 hours allowing slabs to retain their elastic energy and propagation potential.

Now for the WINTER STORM WARNING that goes into effect tonight into Sunday morning.  Talk about a flip flop storm track.  Our mountains were expecting about 2” (5cm) until last night’s model run which showed a more inland track for the weathermaker.  Expectations are up to a foot in the higher terrain of the Whites with snow anticipated to be wet and heavy due to a very thick layer of warm air.  Light snow should begin moving in this afternoon, but should not affect avalanche danger much during daylight hours.  As we move through the evening intensity will pick up and precipitation should be falling in earnest by midnight.  Although this advisory expires at midnight today’s ratings do not reflect what might be developing between 9 and 11:59pm

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.
  • This advisory expires at midnight. 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

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Avalanche Advisory for Tuckerman and Huntington Ravines

Posted 7:30 a.m., Friday February 4th 2011

Tuckerman Ravine has CONSIDERABLE avalanche danger.  Natural avalanches are possible and human triggered avalanches are likely.  The only exception to this rating is the Lower Snowfields which has Moderate avalanche danger and the Little Headwall which is Low.

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger.  Central, Pinnacle and Odell have Considerable avalanche danger.  Natural avalanches are possible and human triggered avalanches are likely.   All other forecast areas have Moderate avalanche danger.  Natural avalanche are unlikely and human triggered avalanches are possible.

Early this morning the summit begin recording the highest wind speeds of the month so far.  February being only 4 days old, the greater point is they are the greatest velocities since the beginning of the last storm which brought between 11 and 15” (28-38cm) to the mountain.  In addition the flow is moving in from the W which is most influential for loading widespread slab in the Ravines.  Therefore as alluded to in Thursday’s advisory today’s loading will increase the concern for natural and human triggered avalanches in most areas due to forecasted wind speeds maxing out at 70+mph (112+kph).  Gusts of 67 and 69 mph were observed between 2 and 3am this morning creating some loading but speeds subsided at daybreak limiting snow movement.  If we stay in the 50mph range we will struggle to meet the Considerable forecast in some areas today.  But the predicted snow showers coupled with higher winds the Considerable rating will come to fruition.  As the day wears on a number of S and N facing slopes like Right gully in Tuckerman and South Gully in Huntington will become cross loaded, but the slopes in the direct lee of W winds will accumulate the most new snow deposition.  The Lip across the Center Bowl to the Chute in Tuckerman Ravine will have the greatest potential for natural activity as winds increase today.  For ice climbers heading into neighboring Huntington Odell through Central will be in the bull’s-eye for W wind deposited slabs.  New loading will also fall on a variety of slabs that were created during the later portion of the storm which may push some of this cold snow beyond what it can handle for load. 

So outside of a brief forecasted snow shower it’s starting out as another bluebird day.  However the expected active loading will require vigilance on your part to watch conditions and give the snowpack a true honest assessment.  Like most individuals when you want to do something (play in the mountains) you’ll be looking for the answer you want so you can do it.  Be objective, the snow is.  What I mean is the snow isn’t thinking “come on hurry up I can’t hold on much longer I’m ready to explode!”  It’s thinking,… well nothing.  When the physical properties of stress versus strength are surpassed… voila… fracture and failure= avalanche.  Snow stability is not with you or against you it just is so study it and it will provide most of the answers.  When you can’t get all the answers be conservative.

Although tomorrow’s snow event has fizzled out to about a 2” (5cm) projection the snow cycles just keep on piling up which makes me smile.  We’ll get into Tuesday’s and Thursday’s snow events in a couple of days, but we are certainly getting into a favorable rhythm to keep the winter mountains freshened up.  Check back early this evening for the Friday Weekend Update on www.mountwashingtonavalanchecenter.org for updates on today’s loading and tomorrow’s new 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.
  • This advisory expires at midnight. 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

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Avalanche Advisory for Tuckerman and Huntington Ravines

Posted 8:28a.m., Thursday February 3rd, 2011

Tuckerman and Huntington Ravines have CONSIDERABLE avalanche danger.  Natural avalanches are possible and human triggered avalanches are likely.   Some dangerous avalanche conditions exist.  Careful snowpack evaluation, cautious route finding and conservative decision making is essential.  The only exception to this rating is the Lower Snowfields and the Little Headwall which have Moderate avalanche danger.

So the big question is what DIDN’T avalanche during yesterday’s storm?   Fracture lines or debris can be seen in most locations in Tuckerman and we’ll get a closer look into Huntington later this morning.  Gully 3, Dodge’s Drop, Hillman’s, the Duchess, Dead End Gully, Left Gully, blah-blah-blah  I would say most angled terrain above 30 to 35 degrees had an avalanche cycle.  Hermit Lake received 15” (38cm) of snow over 48 hours while the summit is reporting 11” (28cm) that fell with moderate wind velocities from the W, S, and mostly from the SE during the majority of Wednesday’s snowfall.  Some low hanging fog hides the Ravines from time to time, but this should blow out to provide good visibility.  When the slopes pop out from the clouds you will see smooth snow with very few crisp fracture lines showing or wind effected snow.  This is because since the last round of avalanches new snow deposition has reloaded previous bed surfaces.  Although wind speeds are expected to increase in the afternoon to about 35mph (56kph) from the N and NW new loading should be somewhat limited today, but certainly something to keep an eye on.  If loading picks up I would be most suspect of S and SE facing aspects.  New snow densities on the summit hovered around 6% with the last couple of inches being even lighter.  This snow will be more tempted to move with light winds today than our average densities around 9-10%.  Therefore natural avalanches are possible under the Considerable rating, but the main rationale for today’s rating is the concern for human triggers.  This stems from light summit snow densities being loaded into soft slabs under cold conditions allowing the snowpack to retain it’s elastic energy.  I would expect the fracture and failure of slabs to have good propagation propensity, which is bad for us.  Don’t let the relatively calm conditions and the blue skies lull you into ignoring what Mother Nature is holding if you step back and take an objective look.  You may find some locations within a forecast area to be below the Considerable rating, but as you get into steeper terrain and high in elevation near the start zones this will likely change.  Being conservative with your terrain choices and giving the snow some time to consolidate is always prudent after a storm, particularly one that came in with light to moderate wind speeds.  Saying this you may have to wait for while because winds will ramp up tonight and may push over 70mph (113kph) from the west tomorrow.  This will generate a significant loading event with a new concern for natural avalanches justifying a Considerable forecast or even High for some areas.  We’ll see how the weather forecast plays out.  This event will be followed by another, albeit more subtle, storm on Saturday/Saturday night.  Check back often and stay on your toes it could be an interesting few 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.
  • This advisory expires at midnight. 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

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Avalanche Advisory for Tuckerman and Huntington Ravines

Posted 7:50a.m., Wednesday, February 2, 2011

Tuckerman and Huntington Ravines both have HIGH avalanche danger today.  Natural avalanches are likely and human-triggered avalanches are very likely. Travel in avalanche terrain is not recommended. The only exception to this rating is the Little Headwall, which has Moderate avalanche danger along with open water and thin cover.  Natural avalanches are unlikely in this area but human-triggered avalanches will be possible as the day develops.

It’s been 2 weeks since the mountain received snowfall greater than 2” (5cm) over the course of a day. Today we will break that trend.  Snow has already begun to fall and the wind has made the swing from W to SE.  Wind speeds are currently around 30mph (48kph) and expected to soon push to 45mph (72kph) with higher gusts. Snow accumulation is forecasted to be around a foot (30cm) by this evening and cold temperatures will hopefully keep it light and fluffy. This lighter density snow is a perfect match for the forecasted winds and I would expect lots of loading without the scouring that we typically see at higher wind speeds.  The areas that will benefit most from wind transport are fortunately enough, the areas that need it most.  North facing aspects such as the Escape Hatch are ill with wanting as past storm events have done little to fill them in.  We expect that they will slide first in a series of avalanche cycles the mountain will see today.  Areas with NE and E aspects such as Hillman’s Highway, Left, South and O’Dell gullies will see significant cross-loading today and natural avalanches are likely to occur. These paths are fairly well developed especially as you move toward a true E aspect.  As a result avalanches should push farther than they have so far this season filling in the talus and covering the vegetation in the ravine floors.  If you’ve gone in “just to take a look” you may be putting yourself at risk of burial as well.  Avalanche terrain includes the run-outs of slide paths. South facing aspects will receive the least amount of wind-loading today but we expect to see avalanches result in these areas from the increased load of the new snow.  Prior to this storm SE aspects contained the snowpack instabilities that concerned us most.  These are now getting buried and further stressed by the weight of new snow.

This storm is expected to pull away tonight and cause winds to wrap to the NW.  The current models are showing wind speeds that are slow to rise as the system pulls out but I wouldn’t be surprised if tomorrow’s weather forecast for the higher summits calls for something higher than the 35mph (56kph) that is now forecasted.  Nonetheless, shifting wind to the NW and the possibility of a couple more inches of upslope snow makes me think we’ll still have elevated avalanche danger tomorrow.  It is possible we will have some lingering instabilities into the weekend from this storm event and the subsequent upslope conditions that will follow.  This will be compounded by another precipitation storm event that looks to be developing for Saturday and Sunday. Make sure you check back in tomorrow morning to get the latest.

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.
  • This advisory expires at midnight. A new advisory will be issued tomorrow.

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

Print Friendly Avalanche Advisory PDF

Avalanche Advisory for Tuckerman and Huntington Ravines

Posted 7:23a.m., Tuesday, February 1, 2011

Tuckerman Ravine: The Sluice, Lip, Center Bowl, Chute, Left Gully and Hillman’s Highway will have Considerable avalanche danger today. Natural avalanches are possible and human triggered avalanches are likely. The Lobster Claw, Right Gully, and Lower Snowfields will 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: South, O’dell, Pinnacle and Central gullies will have Considerable avalanche danger today. Natural avalanches are possible and human triggered avalanches are likely. The Escape Hatch, Yale, Damnation and North gullies will have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.

All I’ve heard for the past few days is “the storm,” “the storm.”  Settle down everyone! It is true that we’ll be seeing some decent snowfall tomorrow and upslope snow showers are expected to continue into Thursday.  And then there’s the system that appears to be tracking our way for Saturday…Oh boy!  Instead of getting too far ahead of ourselves let’s not forget that we currently have instabilities that are worthy of mention on their own.  Yesterday we had essentially all of Tuckerman rated at Considerable and all of Huntington posted at Moderate.  The conditions that drove these ratings still exist for the most part although the threat of naturally-triggered avalanches has temporarily subsided since winds dropped off and blowing snow no longer fills the air. This will change later in the day.  The layers of windslab that were created over the past couple of days are made of what started as light density snow.  As the slab was laid down in wind-sheltered areas it topped loose unconsolidated powder with some of the lowest densities we’ve seen this season.  The combination of the two layers created a decent avalanche cycle though most of the debris was soon wiped out by strong winds.  What remained in place is today’s primary concern. Temperatures dipped down below 0F (-18C) Sunday at midday and have only recently moved back into the positive numbers.  Arctic temperatures do a fine job of preserving energy stored in the snowpack and instabilities can persist far longer under colder temps.  Up to 3in (7.5cm) of new snow today will add additional load and therefore stress to these weaknesses. The day’s wind is expected to shift from the W to the SW with speeds at the lower end of what’s needed for measureable wind transport.  The National Weather Service is calling for slightly stronger winds and if we meet their forecasted speeds of 40mph (64kph) with higher gusts we could see areas pushing the upper end of their forecasted ratings by late in the day.  If the wind stays just a bit lower loading will be minimized and the stress applied to the slopes by the new snow should be largely uniform.

In Tuckerman, the areas of most concern are the Sluice, Lip, Center Bowl and Hillman’s Highway. All of these areas received loading through the morning yesterday and they’re also well positioned for additional loading if the winds reach the upper end of their forecasted speeds.  In Huntington it’s the bottom of South Gully and above the ice bulge in Central that concern me most. South had more loading occurring yesterday morning than anywhere else in that ravine and Central had avalanched but only the section below the ice bulge.  Plenty of hangfire remains in place above.  Scattered around both ravines you will find a fair amount of old surface that was uncovered by recent wind or avalanche activity.  It provides the most stable travel option so watch for old tracks and a difference in surface texture as clues to where it’s exposed prior to new snowfall.

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.
  • This advisory expires at midnight. A new advisory will be issued tomorrow.

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

Printable Advisory