Avalanche Advisory for Sunday, 3-31-2013

This advisory expires at 12:00 midnight tonight.

Tuckerman and Huntington Ravines have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

Before we begin, let me remind everyone that Low avalanche danger does not mean no avalanche danger. It can often come pretty close to that after strong melt-freeze cycle or other similar events, but we’ve had no such event that would put the snow at the lower end of the Low rating. Instead, we’ve come to today’s rating through a combination of settlement over time, solar gain and mild temperatures, and numerous volunteer stability testers (e.g. skiers, ice climbers, and even a large German shepherd rag-dolling in the Lip).

You’ll find a variety of snow conditions as you move around in the ravines. Yesterday was bright and sunny up here, though it stayed deceptively cool throughout much of the day. Aspects facing strongly to S did receive enough heating to moisten the surface, and in some cases made for heavy wet snow. I found this to be the case beneath North and Damnation gullies in Huntington, but as a traversed underneath Yale, a slightly different aspect, the solar gain was much less noticeable. By the time I got to NE and N aspects, it was clear that the snow had remained cold and dry. Tuckerman was much the same, with Left Gully staying dry and Right Gully being wet. Between these two areas the snow will range from dry windblown to crusty chopped up that will make you hope the sun can work its magic on the slopes.

Avalanche concerns today are a little different than a typical Low, where we advise people to “watch for unstable snow in isolated terrain features” or sometimes we refer to isolated pockets. The thing that gets my attention today is the potential for someone to hit an isolated trigger point in an area that did not get tested a lot by skiers or climbers yesterday. For certain, there were a lot of skiers getting into the Lip, Chute, and left side of the headwall. Areas that weren’t thoroughly tracked up are the ones to watch for, such as the icefall area and the Sluice in Tuckerman and above the ice in Odell and Central in Huntington. Overall stability in these locations is good, but there may be weak points near buried rocks or ice, or at the edges of slabs. If something were to release in these locations it would be too large to call it an “isolated pocket”. With this in mind, my advice is to stay vigilant to changing snow conditions, keep up the habit of using safe travel practices, and pay attention to who is above or below you.

We’ll see clouds on the increase later today and precipitation beginning as early as this afternoon. It would be a good day to get an early start. The John Sherburne Ski Trail saw above freezing temperatures yesterday and plenty of traffic. This means conditions will be similar to a resort whose groomer has been broken down for a week. Hopefully warmth will soften it again this afternoon.

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 at 8:30a.m., March 30, 2013. 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

2013-03-31 Printable

Avalanche Advisory for Saturday, 3-30-2013

This advisory expires at 12:00 midnight tonight.

Tuckerman Ravine has MODERATE and LOW avalanche danger today. Lobster Claw, Right Gully, The Sluice, the Lip, Center Bowl and Chute have MODERATE avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Of these, the Lobster Claw and Right Gully are at the lower end of the Moderate rating. Left Gully, Hillman’s Highway, the Lower Snowfields and the Little Headwall have LOW avalanche danger. Natural and human triggered avalanches are unlikely in those locations. Watch for unstable snow on isolated terrain features. 

Huntington Ravine has MODERATE avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully. South Gully and Escape Hatch are at the lower end of this rating. 

The mountain has cleared already this morning as of 7:00am. This will allow a full day of heating today on south facing aspects today and contribute to our concerns about human triggered avalanches to warrant a Moderate rating.  Yesterday’s new snow mostly blew down into the mid-elevation start zones of lee gullies.  Steeper parts of these  areas are the focus of concern today.  The concern is generally limited to these recent new snow layers losing strength as they warm and possibly fracture and fail. A shallow slab could entrain more snow on it’s descent but do not forget the poorly bonded interface at the mostly deeply buried ice crust . In Tuckerman Ravine, I would be most concerned about the surface slab problem in the climber’s left fork of Lobster Claw,  the large climber’s left hand pillows near the top of Right Gully, the steepest section of the Sluice and the Lip. The belly of Right Gully and the main gully in Lobster Claw received a lot of “skier control work” recently which generally cut up the slab but the steeper drop-ins in Right Gully and the climber’s right fork of Lobster Claw could release if the right trigger is applied in the right spot.

Another concern of a different nature is the pooled rimed snow which has sluffed over the ice in Center Bowl and the upper part of Chute and which may lurk elsewhere.  An experienced party wisely abandoned an attempt to ski the Chute yesterday when they began to wallow in waist deep snow on their way through the narrow, choke point which avalanched recently and has now reloaded as a result of this “sluff loading”.  Left Gully should provide dry snow for skiing with some windloaded pockets here and there.   Remember that our areas rated at Low remain exposed to hazards from above. For example, a poorly chosen approach to Left Gully puts you in the runout of Chute and sections of the Lower Snowfields are threatened by the Duchess so stay alert plan for worst case scenarios. 

In Huntington, fairly well developed snowfields exist near the top of Damnation, the mid section and adjacent to the Harvard ice bulge in Yale, as well as below and above the first ice pitch in Central. Look for sluff loading in Pinnacle at the base and to a lesser extent in the mid-section.  More easily avoidable pockets of slab on Odell, South and Escape Hatch also exist.  

This is the first spell of intense warming that we have had for some time so all the issues you’d expect from rocks, ice and slabs of snow heating should be on your radar today.   The other issue will be the amount of human triggers overhead who may not see you or may not know how to avoid hazards. People innately seek the comfort of others in steep terrain  so don’t be distracted from safe travel guidelines by others who may be taking uncalculated risks by booting up avalanche tracks.

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 at 8:30a.m., March 30, 2013. A new advisory will be issued tomorrow.

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

2013-03-30 Print friendly

Avalanche Advisory for Friday 3-29-2013

This advisory expires at 12:00 midnight tonight.

All forecast areas of Tuckerman Ravine and Huntington Ravine have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully and identify features of concern. The only exceptions to this rating are the Little Headwall, which have Low avalanche danger. Natural and human triggered avalanches are unlikely in these areas except in isolated pockets.

Another day, another uncertain upslope snow event. That was the focus of our forecaster meeting this morning. Several times this month we’ve seen upslope events drop much more snow than expected, and other times not much materializes. Yesterday we had the latter, with only 0.5” of snow falling on the summit and a dusting around Hermit Lake. Today’s forecast is similar to yesterday’s, with a trace to 2” (0-5cm) in store with NW winds blowing 25-40mph (40-65kph). The range of snow makes for a challenging avalanche forecast and puts more of the burden on you to pay attention to what is actually taking place throughout the day. (Of course, this is no different than what you should always be doing.)

Let’s start with the scenario that would produce the greatest avalanche concerns. Let’s suppose we do get 2” of snow with summit winds blowing at the upper end of the rating, around 40mph with some higher gusts. There have been approximately 3” of snow which has fallen in the past couple days, so we’d be looking at a grand total of about 5” of snow available for loading into lee slopes. That’s a lot of snow to be loaded into slabs in the ravines. Expect these to be pretty soft and weak in the most protected locales, such as the Center Bowl or Central Gully. Most other areas would also develop fresh new slabs under this scenario, whether through direct loading or cross loading, and the problems would most likely be found in the middle to the top of the gullies or slide paths. If it plays out, this worst-case scenario would have some areas pushing the upper limits of the Moderate rating. As one who travels frequently in avalanche terrain, this is the scenario I’d be expecting, that way I’m not disappointed when I decide to turn back due to worsening conditions.

I’ll preface the following scenario with the fact that wind speeds have already exceeded the 40mph mark. In this alternative best-case scenario, suppose winds do become light, around 25mph, and we only receive another trace amount of new snow. This may produce smaller pockets of unstable snow, but would limit the widespread development of slabs. Prior to the upslope snow of the last couple days (i.e. before Wednesday), stability was generally good. Some areas, such as Hillman’s and Left, had very stable snow. Others had mostly very stable snow with smaller areas of concern; Right Gully and Lobster Claw are examples. The center portion of Tuckerman, from the Sluice through Chute, had fairly good stability, but if one were to trigger something here it could be sizeable. In the absence of significant new wind loading from yesterday and into today, we’re left with good underlying stability, but will have concerns for human triggered avalanches in the uppermost slabs. In this situation with little snow and light winds, some areas would have difficulty getting into the Moderate range.

Hopefully you can see the range of possibilities today. Don’t expect to see much of the ravines today, they’re thickly in the fog at this time and we may not have much of a break until tomorrow. Speaking of tomorrow, we’ll be posting a Weekend Update later this afternoon with our thoughts on what’s in store for the coming days. Look for it in The Pit section of our website.

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 at 8:30a.m., March 29, 2013. 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

2013-03-29 Printable

Avalanche Advisory for Thursday 3-28-2013

Expires at Midnight 3-28-2013

Tuckerman and Huntington Ravines have MODERATE avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible.  Heightened avalanche conditions in specific terrain features exist.  Evaluate snow and terrain carefully to identify features of concern.

The dreaded “trace to 2″” has reared it’s head for both today and then once again for tomorrow.  These upslope snow events can be hard to deal with from a weather and avalanche forecast point of view.  If we get a trace obviously not much change will occur to avalanche danger, but if we exceed expectations a bit and if the winds are right, well then we can have some real problems.  These scenarios are a real challenge from the forecaster’s chair for us, and for you in the field.  Therefore it is critical that you pay attention to what is actually happening weather and avalanche wise as the day continues and use all your avalanche training and experience to make good choices.  Here’s my take on today’s situation.

Beginning yesterday afternoon light snow showers began and continued for 12 hours to about midnight delivering about 2.5″ (6cm) of snow on the summit.  This precipitation was brought in on a NW to NNW wind between 25 and 45mph (40-72 kph).  Early this morning winds shifted quickly and briefly came from the ENE before heading back through the NE at about 25mph (40kph).  They are expected to head back to the NW today and increase to about 40 mph (65kph). All the while, up to an additional 2″ (5cm) of snow is expected.  When adding Wednesday’s snow to today’s accumulation potential, with a moderate wind moving back and forth from the NW to the NE and back again, we have concerns for south facing slopes and gullies.   Specifically our concerns are focused on the Lobsterclaw, Right Gully, the Sluice, and the Lip in Tuckerman and North, Damnation, Yale, and Central gullies in Huntington.  These locales are in the direct lee of today’s anticipated wind.  I would also have an eye on crossloading in some areas facing E, however our historical experience with today’s anticipated wind speeds this should be quite limited.  The aforementioned gullies and slopes with a strong S facing component should pick up new wind slab in their upper start zones.  I would generally expect the main instabilities to be focuses near the rim where gullies top out. If we do receive closer to 2″ than a trace expect to be on the upper end, bumping the ceiling, of the “Moderate” rating definition hedging towards “Considerable”.  Begin thinking about natural avalanches moving from “unlikely” to being “possible”. Also, lookout for snow piling beneath ice bulges and forming slabs.

To recap the main points for the field today.  1.  Winds have moved from the NW to the NE and are now moving back to the NW from 25-45mph.   This will load new snow into mainly S facing aspects.  2.  Whether yesterday and today’s total snowfall is 2.5 or 4.5″ will make a big difference on whether we sit at Moderate or start leaning towards Considerable for S facing slopes.  Watch the weather and snowpack closely to make good choices.  3.  Look out for some isolated pockets of deeper slab below steep ice bulges and other midslope benches particularly in Huntington Ravine.  4. Much of our terrain will have good to very good stability if windspeeds do not increase and and new snowfall is light.

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 at 7:50am, March 28, 2013. 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

2013-03-28 Print friendly

Avalanche Advisory for Wednesday March 27, 2013

This advisory expires at midnight 3-27-2013

Tuckerman Ravine has Moderate and Low avalanche danger today. The Sluice, Lip, Center Bowl, and 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, however, watch for unstable snow in isolated terrain features.

Huntington Ravine has Low avalanche danger today. Natural and human triggered avalanches are unlikely, however, watch for unstable snow in isolated terrain features.

Although barely worth noting due to scant amounts, yesterday marked the 15th day in row, and the 23rd day of the month, that the higher elevations have received precipitation.  This streak will continue as a system approaches the region later today, expected to give the landscape a 3-5” (7.5-12.5cm) shot of snow.  I’ll say more on this developing weather event in a minute.

Tuesday gave us good conditions to spend copious amounts of time in the field.  Our assessments in Hillman’s Highway, Left gully, and the greater Lip area verified the morning advisory ratings.  Locations posted at Moderate still harbor enough concern to keep them a step above Low, however another day of consolidation has certainly brought these slabs closer to this lower rating.  The likelihood of a human trigger is still “possible”, but on the spectrum we are closer to the “unlikely” descriptor than “likely” when looking at the neighboring definitions of Low and Considerable.  The variability of slab hardness and thickness are still the two main factors on your ability to trigger these slopes from the Sluice over to the Chute.  It will be important to evaluate the snow stability under foot/ski as you move due to these changing slab properties.  Pay particular attention to the propensity for a slab to fracture and propagate leading to failure as you enter it’s thinnest outer edges.  This is a common cause of our post storm human triggered avalanches.   In addition to thin slabs over a weak layer, you may also enter small lee areas in the terrain that were more protected from wind hardening than nearby slopes, which kept them a bit softer and weaker.   The main point of both of these examples is to pay attention to changing stability as you move in the terrain.  Also be weary of trusting and extrapolating earlier stability tests even though slope angle and aspect are similar.   By evaluating snow and terrain carefully the experienced and skilled mountain climber and skier should find reasonable routes within areas posted at Moderate until snow develops new problems late in the day.

3-5” (7.5-12.5cm) of snow is anticipated to begin late in the day, fall through the night, and perhaps into daylight tomorrow morning.  This entire weather event shouldn’t play too much of a factor on stability for the typical recreational period today.  I am cognizant that technically this advisory is valid until midnight so realize as we enter the last hours of the day avalanche danger may have increased enough to warrant a rating increase.  But obviously this is more of a concern for those benighted than those intentionally recreating.  It would be wise however to watch for new precipitation issues if it begins a bit earlier than forecasted.  If snow falls in the early to mid-afternoon you can anticipate some thin new slabs today in strong lee slopes protected from NW winds.  Areas currently at Moderate would be the first affected, but not enough to move them to a higher rating.  As snow falls overnight winds will shift through the N to the NE.  You can expect some new slab avalanche concerns tomorrow on slopes with primarily a S facing component.

 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 at 8:10 Wednesday 3-27-2013.   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

2013-03-27 Print Version

Avalanche Advisory for Tuesday, 3-26-2013

This advisory expires at 12:00 midnight, March 26, 2013.

Tuckerman Ravine has Moderate and Low avalanche danger today. The Sluice, Lip, Center Bowl, and 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, however, watch for unstable snow in isolated terrain features.

Huntington Ravine has Low avalanche danger today. Natural and human triggered avalanches are unlikely, however, watch for unstable snow in isolated terrain features.

Compared with yesterday, avalanche danger ratings have dropped one rating across the board. Areas that were Considerable yesterday are now Moderate; those that were Moderate are now Low. I say this not to give you the green light to forget everything you learned in your avalanche class and blindly climb or ski every line you want, but to highlight the idea that just yesterday avalanche danger was rated higher. There are still avalanche problems to contend with, even in areas rated at Low danger.

The first problem you’ll want to know about is the leftover slab from weekend snow and wind loading. This triggered some large natural avalanches that left behind sizeable hangfire. The slabs that developed but didn’t avalanche during this event have now had a couple days time in which to work towards stabilization. In many locations, you’ll find thick strong slab that would be difficult to trigger. However, there may be more easily triggerable points lurking under the snow. These include locations where the dense slab is thinner or softer, allowing the stress bulb from your skis or boots to penetrate deeper, perhaps to a weak layer. Another example is where there is a greater difference in density between the firm upper layer and the soft lower layer. This implies weaker snow below, which could act as the weak layer. Yet another example is where windloading took place on a prior bed surface from avalanches over the weekend, such as in the Sluice, Lip, and Center Bowl. These problems are mostly found in the Moderate rated areas, but smaller terrain features, such as the steep skier’s right side of Right Gully, are locations where you can also find them. You’ll stand a good chance of finding reasonably stable snow if you go looking for thick strong slabs with little change in density as you look deeper.

The second problem is one that may develop today. Last night we received a dusting of new snow (2-2.5cm) which may be blown into the upper start zones by 25-45mph (40-70kph) NW winds. This will be a lesser concern than the existing slabs, but if you see it developing you may want to take notice of it. Expect S, SE, and E aspects to receive the most additional wind loading.

Our terrain has turned a corner and now feels “big” to me, whereas throughout this season it seemed much less imposing. We’re at the point of the season where your safe travel practices and ability to assess the snowpack in a spatially variable environment can lead to a positive experience in the ravines, and may allow you to take some runs from the tops of the routes.

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 8:30 a.m. Tuesday, March 26, 2013. 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

2013-03-26 Printable

Avalanche advisory for March 25, 2013

This advisory expires at 12:00 midnight, March 25, 2013.

Tuckerman Ravine has  CONSIDERABLE and MODERATE avalanche danger today.  The Sluice, the Lip, Center Bowl and Chute have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. All other forecast areas in Tuckerman Ravine 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 in that location.

Huntington Ravine has  MODERATE avalanche danger. All forecast areas have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully to identify features of concern.

Brief windows of decent visibility provided Chris and I some snapshots  of our current conditions in Tuckerman and Huntington yesterday. The most striking feature was the depth of the avalanche debris that ran across the floor and down towards Connection Cache.  The second most striking feature was the areas of slabs remaining above the new crown lines in Sluice, the Lip and Center Bowl.  These start zones, plus some others are the targets for our discussion today and the major areas of concern where we feel that the likelihood of human triggered avalanches pushes these areas into the Considerable rating. I don’t expect any natural avalanches to occur since no natural triggers such as new snow, rapid warming or windloading are forecast today. However, the hangfire in the Considerable rated areas as well as in upper start zones on the buttress between Right and Sluice, the upper part of Sluice and the Lip, across the Center Bowl to the now very deep sluff pile in Chute are all pretty ripe for avalanching.  The slab in the Sluice is now sitting on the January rain crust which has been the bed surface for two avalanche cycles now, both of which left crown lines 18-36″ deep and 60-100m wide. The two crown lines in Sluice are barely visible due to reloading.

Other areas of concern in Moderate rated gullies are wind loaded areas in the lee of the strong northwesterly winds that we experienced on Saturday. The skier’s right side of both forks in Lobster Claw and the upper skier’s right sides of Right Gully as well as the drop-in on the climbers right of Left Gully are all areas worth evaluating very carefully.  The snow was laid in there quite deep making a journey through these gullies a challenging exercise in terrain management and snowpack evaluation for anyone.

Huntington Ravine has many areas of wind deposited snow, some of it soft windslab, to be concerned about.  A brief window of visibility this morning and yesterday afternoon revealed some scouring near the tops of Damnation, Yale,  and Central but loading in the mid sections and at the gully bottoms.  Pinnacle and Odell experienced scouring on the approach and the first pitch of Odell.  The middle pitch and top out of Pinnacle is unknown and well worth watching.  The middle of Odell and South have pillows of slab deserving of their Moderate rating.

The Little Headwall has some holes in the streambed and some ice to deal with but it is skiable. Though still bushy, the Lower Snowfields can provide some good skiing and riding but don’t ignore the significant threat that looms above in the Duchess and the lower reaches of Deadend Gully. Many folks ski on the treed slope below and between the mouth of Right Gully and Lobster Claw. The trick is to avoid the runouts of all the gullies and to bear in mind that the slope has a steep section of windloaded snow near the base of the cliff as well as some pockets in the middle which can avalanche so use solid travel skills in this terrain. The floor of Tuckerman has filled in substantially from the Center Bowl avalanche.  Overall, we are set up well for the coming weeks of spring skiing.

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 8:30 a.m. Monday, March 25, 2013. A new advisory will be issued tomorrow.

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

2013-03-25 Print friendly

Avalanche Advisory for Sunday, 3-24-2013

This advisory expires at 12:00 midnight, March 24, 2013.

Tuckerman Ravine has  CONSIDERABLE avalanche danger today.  Natural avalanches are possible and human triggered avalanches are likely. All forecast areas in Tuckerman Ravine have Considerable avalanche danger. The Little Headwall has Low avalanche danger. Natural and human triggered avalanches are unlikely in that location.

Huntington Ravine has  CONSIDERABLE and MODERATE avalanche danger. Central, Pinnacle, Odell, and South gullies 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.

Old man winter lashed out furiously yesterday.  Northwesterly winds gusted over 100 mph (160 kph) frequently yesterday morning and then again around 6 pm with wind holding steady in the 70-90 mph (110-145 kph) range for the past 36 hours.  Forecasted upslope snow again surprised us with it’s intensity through the day so it was no surprise that the summit recorded about 6″  (15 cm) of new snow.  We recorded 20 cm (close to 8″) at our wind sheltered snowplot at the Harvard Cabin. Though both ravines that we forecast remain shrouded in fog, there is no doubt that the new snow and high winds resulted in natural avalanche activity yesterday and/or overnight. How widespread and which gullies ran will remain to be seen this afternoon when forecasted clearing will hopefully  allow us to get into the field for a closer look. Though diminished visibility for the past 36 hrs has reduced our ability to forecast with the high level of detail that we all like, several factors allow us to lower the danger ratings from yesterday while remaining conservative.

Windspeeds over 100 mph (160 kph) generally scour the gullies in Huntington Ravine but allow more loading and crossloading in gullies with a similar aspect in Tuckerman Ravine due to it’s lower, slightly more sheltered location from northwest winds. Our windslab problem usually reaches its zenith during the wind event when avalanches tend to occur due to the great weight of the new snow rapidly overwhelming the strength of a weak layer.  Though we have turned the corner today on the rapid loading due to diminishing winds, there is still the risk that today’s upslope snow, falling on moderate winds, could trigger a natural avalanche in Considerable rated areas. This fact coupled with an inch or two of snow falling on moderate winds in the loading speed range, lead us to believe that human triggered avalanches are pushing the upper end of the definition of moderate in areas so rated. Improving weather conditions today will increase the likelihood of a person traveling into a start zone and triggered an avalanche that could sweep the floor of Tuckerman Ravine, so I would consider the consequences carefully before entering this area.  The Huntington Ravine gullies will have piles of snow at the start of the gullies and on the approach to the steep bits of ice.  We have had plenty of examples of people triggering deep slabs in the lower reaches of  Central, Pinnacle and Odell gullies following similar weather conditions.

Refer to the photo gallery and you will see that many of our start zones and bed surfaces have increased in size and smoothed out quite a bit due to the 20″ of snow which fell on Tuesday and Wednesday (March 19-20) resulting in the possibility of much larger avalanches that will run further than they have all season.  Remember too that snowfall in the early stages of yesterdays wind event will form a softer layer lurking beneath the harder windslabs on top so frequent digging to find this layer would be critical to avoid being fooled by the firm snow on top for those choosing to tangle with avalanche terrain today.

Lots of soft snow exists on lower elevation treed trails and slopes like the Sherburne ski trail.  The Little Headwall has some holes in the streambed andsome ice to deal with but it is skiable. Though still bushy, the Lower Snowfields could provide some good skiing and riding but don’t ignore the significant threat that looms above in the Duchess and the lower reaches of Deadend Gully. Many folks ski on the treed slope below and between the mouth of Right Gully and Lobster Claw. The trick is to avoid the runouts of all the gullies and to bear in mind that the slope has a steep section of windloaded snow near the base of the cliff as well as some pockets in the middle which can avalanche so use solid travel skills in this 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 8:30 a.m. Sunday, March 24, 2013. A new advisory will be issued tomorrow.

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

2013-03-24 Print friendly

Avalanche Advisory for Saturday, 3-23-2013

This advisory expires at 12:00 midnight, March 23, 2013.

Tuckerman Ravine has HIGH and CONSIDERABLE avalanche danger today. Very dangerous avalanche conditions exist; travel in avalanche terrain is not recommended. Right Gully, the Sluice, Lip, Center Bowl, and Chute have HIGH avalanche danger. Natural avalanches are likely and human triggered avalanches are very likely. Lobster Claw, Left Gully, Lower Snowfields and Hillman’s Highway have CONSIDERABLE avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. The Little Headwall has Low avalanche danger.

Huntington Ravine has HIGH and CONSIDERABLE avalanche danger. Central, Pinnacle, Odell, and South gullies have HIGH avalanche danger. Natural avalanches are likely and human triggered avalanches are very likely. All other forecast areas have CONSIDERABLE avalanche danger. Natural avalanches are possible and human triggered avalanches are likely.

It’s been a long time coming, but winter finally seems to have arrived in full force. Today will have conditions to rival the most rugged winter day. Near zero visibility, blowing and drifting snow, very strong winds, and cold temperatures will make it a good idea to stay lower on the mountain. Travel into the ravines and above treeline will be tough, and in the case of the ravines, carry the additional risk of large avalanches running farther downslope than they have yet this season. I do not recommend you go into the floor of Tuckerman or Huntington to “have a look” due to the risk of large avalanches today.

The last week has been eventful for snow lovers. We had a good storm on Tuesday followed by a windloading event on Wednesday that produced some good avalanches and left many slopes loaded with slabs. Since then, we’ve had over 6″ (15cm) of additional upslope accumulations, most of which came yesterday evening. Upslope snow showers continued through the night and will continue today, bringing another 2-4″ (5-10cm)during the day. From what we’re seeing on the ground, I wouldn’t be surprised if we exceed the forecasted total. This all adds up to a lot of snow being available for loading into avalanche paths. The wind will be the driving force that moves all this snow. Overnight NW winds increased in speeds, reaching a peak gust of over 100mph (160 kph) while writing this advisory. Expect all aspects and elevations to develop new windslabs. There is a chance that some areas, mostly those in Huntington, will be hammered into very strong hard slab by the strong winds, but this isn’t something I’d be willing to bet my life on. The differences between areas rated High and those rated Considerable are based on how they typically react to strong winds speeds as well as their previously existing slabs and bed surfaces.

Throughout today, I expect windloading to be significant in most areas of Tuckerman, likely producing multiple avalanches in the ravine, with some paths possibly running more than once. Due to the high wind speeds and new snow mixing with old redistributed snow, slabs that form today will be dense. These can build into large deep slabs that can cause a lot of destruction when they fail. We will wait this one out and only get up to see what happens after the avalanche cycle calms down a good bit.

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 8:30 a.m. Saturday, March 23, 2013. 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

2013-03-23 Printable

Avalanche Advisory for Friday, 3-22-2013

This advisory expires at 12:00 midnight, March 22, 2013.

All forecast areas of Tuckerman and Huntington Ravines have MODERATE avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Heightened avalanche conditions exist. Evaluate snow and terrain carefully and identify features of concern. The only exception is the Little Headwall, which has Low avalanche danger. Watch for unstable snow in isolated terrain features here.

Today we are treated to an unexpected bluebird morning in the ravines, which is allowing us to get great visual observations of what’s taken place here since the latest storm began. On the whole, it’s definitely a “heads up” kind of Moderate today. The storm dropped a large quantity of snow across the mountain, which was subsequently blown into the ravines on strong NW winds and produced numerous avalanches in many locations. Recent avalanche activity is a red flag that should heighten your awareness of the avalanche risk. This morning that red flag is standing straight out and strong in the relatively windless ravine. If winds increase as forecasted and additional snow loading begins to occur, that is another red flag and should cause you to reconsider whatever plan you have made. 

The stability problems we’re dealing with today are the result of the aforementioned storm and wind event. Snow began on Tuesday, but it wasn’t until Wednesday morning that the winds shifted to the NW and increased in speed. This created a situation of significant windslab development across all aspects. Avalanches occurred at various times during the storm, which allowed some slopes to see a lot of reloading while others still show sharp crown lines indicating they took place later in the avalanche cycle. Thursday ended with clear skies and some solar gain on S-facing slopes. This created a sun crust on some of these aspects, but I doubt that the sun’s effect was strong enough to completely stabilize these slopes. In fact, it just might be enough to provide a false sense of stability if one were to only make assessments in the upper layers, such as with a ski pole probe or the feel of snow beneath one’s skis.

We often are able to pick out a couple specific areas where we have our greatest concerns. Today, new windslab is sufficiently widespread to make just about all areas an “area of concern.” For example, in all locations of Tuckerman I would be cautious about venturing up without a clear idea of why I was going there. Sluice did have a recent avalanche, but there is still a large amount of hangfire sitting in very steep terrain above the crown line. The Lower Snowfields, Right Gully, and Lobster Claw are the areas with the lowest likelihood of avalanches today, but they still easily fall within the Moderate range.

Huntington has stability concerns in many areas as well. In Yale, Damnation, and North, the problems are greatest in the mid-sections of the gullies. Central has a lot of new slab throughout. Pinnacle and Odell have slab on the approach to the ice as well as up above the ice. We’ve had lots of accidents and close calls on these approaches after similar events, so be sure to begin assessing snow carefully long before you swing a tool. South and Escape Hatch have a lot of windslab near the exits. So as you can see, the problems truly are widespread today.

Enjoy the sunshine while we have it. The forecasted weather was for summits being firmly entrenched in fog, so visibility may deteriorate rapidly at any time today. We’ll have an Weekend Update for you this afternoon or evening after our field work 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 8:40 a.m. Friday, March 22, 2013. 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

2013-03-22 Printable

Avalanche Advisory for Thursday March 21, 2013

This advisory expires at Midnight 3-21-2013

Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger.  The Lip, Center Bowl, Chute, and Left Gully have Considerable avalanche danger.  Natural avalanches are possible and human triggered avalanches are likely.  The Lobsterclaw, Right Gully, the Sluice, Hillmans Highway, The Lower Snowfields, and the Little Headwall have Moderate avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible.

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger.  Central, Pinnacle, Odell, and South gully have Considerable avalanche 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 avalanches are possible.

Another 8″ (20cm) on Wednesday was recorded on the summit totaling 24″ (60cm) for the storm and 40″ (102cm) for the week! Ideal loading from moderate and high NW and W winds have given both Ravines BIG gains in the last 2 days.  Although some clouds are hiding all the ravine secrets a number of gullies and slopes have both avalanched and grown substantially.  In Huntington, natural avalanche evidence can be traced to Damnation, Yale, Odell, and South gullies.  I would suspect Central avalanched as well but it is not evident.  In Tuckerman avalanche debris can be seen under Dodges Drop which ran into Hillman’s, Hillman’s Highway, the Duchess, and the Sluice. The Sluice ran big.  A deep fracture line remains across the steepest part of the Sluice, to the climbers left of the water ice.  It rips down to the Open Book area near Lunch Rocks, and appears to head up into the Knife Edge towards Right Gully.  Joe and I look forward to seeing what she left in her wake on the floor of Tuckerman later this morning.  Currently no fracture lines are visible in the Tuckerman Center Bowl which tells me an avalanche cycle occurred early in the storm and has reloaded.

Early this morning light snow fell on a dropping NW wind, currently blowing at +/- 35mph.  This falling velocity trend is expected to continue which will limit new loading for most of daylight hours.  Tonight this will all change again with increased winds and more light upslope snow.   Generally, what we’re dealing with today is the concern of human triggered avalanches being between “possible” and “likely”.  Areas posted at Considerable have grown substantially and are mostly devoid of any wind effect evidence-i.e. smooth, they are also recently loaded from an overnight WNW wind.  Some of these rated areas have become much larger such as Odell and Central in Huntington and The Lip in Tuckerman.  You will likely find multiple layers, some quite thick, with varying weaknesses from this storm.  This is due to wind speeds ramping up and down, as well as a plethora of crystal types from large stellars to heavily rimed graupel.   All other forecasted areas are either a solid Moderate or are sitting on the upper end of the rating.  You can expect more obvious spatial variability in the Moderate forecasted area than those posted at Considerable.  Anticipate wind effect sastrugi, a little old hard surface, and areas of unstable new slab.  This diversity is well demonstrated in Lobster Claw and  Right Gully.  In Huntington’s Yale and Damnation wind effect is less obvious, but the size of instabilities are smaller due to their tighter ribbon like nature compared to slopes found in Central and Odell.

It is a heads up day with all forecast areas teetering between Moderate and Considerable right after a storm. This is exactly the conditions that get people in trouble worldwide causing avalanche accidents.  The vast majority of backcountry users stay away from avalanche terrain during very obvious “High” avalanche danger in the midst of the storm.  However, as instability decreases and the blue skies erupt, powder hunger tempts gluttons to get after it.  This is a dangerous scenario.  There can be reasonable options for a skilled user with good avalanche knowledge, but a honest, objective assessment is critical to overcome your bias to jump into the steep and deep.  Cautious route finding and conservative decision making is essential to come back and play again in the mountains.

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 8:55 a.m. Thursday 3-21-2013. 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

2013-03-21 Print Version

 

Avalanche Advisory for Wednesday March 20, 2013

Expires at midnight, Wednesday 3-20-2013

Tuckerman and Huntington Ravines have HIGH avalanche danger.  Natural avalanches are likely and human triggered avalanches are very likely.  Very dangerous avalanche conditions exist. Travel in avalanche terrain is NOT recommended.

As of midnight on this first day of “Spring” the summit of Mount Washington received 16” (41cm) of new snow with an average density of 6.2%.  Since then it’s been lightning up a bit, but upslope snow continues to fall which will likely bring us close to 20” by the time it all shuts down.  This storm is closer to what I remember over the years as a classic compared to the recent events over the past couple of seasons.  The storm came in dropping its snow from the SE and the SSE with moderate winds, which is typical, but then immediately wrapped to the NW and W with an increased wind velocity.  Most of our storms this season have lingered from the NE or N for a day robbing us of great snow loading events, but not this one!

Winds from the NW shifting to the W will increase through the day reaching 80mph late this afternoon.  This will move large volumes of snow into all our forecast areas through direct and cross loading.  Wind speeds will likely peak between 6pm and 4am before dropping through tomorrow and becoming light.  In addition to all the snow available for transport from alpine zones, upslope snow will give us some more from the sky with 2-4” today and 1-4” tonight and tomorrow.  I expect widespread natural avalanche activity on a variety of slope angles and aspects, some of which will be quite large.  The largest of which will come from the area from the Sluice through the Center Headwall of Tuckerman. It is an excellent day to take advantage of lower mountain trails or lift serve skiing and riding to avoid avalanche terrain.  The Sherburne ski trail should be in very good shape this morning before winds start sculpting the upper half. The Gulf of Slides ski trail should also be enjoyable, but be sure to avoid the obscured avalanche paths that historically cross the trail in its upper reaches.

Avalanche activity today and high scouring winds overnight will both likely give us a whole different scenario tomorrow.  Be sure to read Thursday morning’s advisory before venturing into 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 8:20 a.m. 3-20-2013. 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

2013-3-20 Print Version

Avalanche Advisory for Tuesday, March 19, 2013

This advisory expires at 12:00 midnight tonight.

Tuckerman Ravine and Huntington Ravine have CONSIDERABLE avalanche danger today. Natural avalanches are possible and human triggered avalanches are likely. Dangerous avalanche conditions exist. Careful snowpack evaluation, cautious route-finding, and conservative decision-making are essential.

It’s ironic, isn’t it? On the last day of winter 2013, what will likely be the largest winter storm to hit the White Mountains yet this season has arrived. While snow accumulations are already on the rise, so is the avalanche hazard. During this storm, I expect avalanche danger to push the boundaries of the Considerable rating. The risk of naturally triggered avalanches is significant, and your ability to assess the risk from below will be very poor, so think hard about even going into the bottoms of any slide paths today, especially the floor of Tuckerman. I don’t want to play Debbie Downer and ruin the celebration of the last day of winter, so let me simply suggest that the party take place outside of avalanche terrain. Resorts, backcountry ski trails, and below treeline gladed areas around the mountains would be good options.

Yesterday’s field work provided a lot of information to give us a baseline for where we’re starting out today. All areas of Huntington, Hillman’s Highway, Left Gully, the Chute, and far left side of the Center Bowl all had very good stability, with exceptions in small pockets here or there. This was due to strong winds scouring snow away or packing it into stiff slabs that would require some force to stick a pencil into. In more protected locations, e.g. the Lip and Sluice, the wind has less effect and therefore the surface slabs developed less strength. Beneath both the softer and the harder slabs, there was a weak layer composed of snow crystals deposited Sunday as well one over the latest rain crust from last Tuesday. This is the weak layer that failed and caused a 70cm deep hard slab avalanche in the lower Chute area on Sunday night. It’s also the reason why I think any avalanches that take place today in the Bowl, Lip, or Sluice may step down into this hard layer and significantly increase the size and consequences of the slide.

So far today, we’ve got about 4″ (10cm) of new 10-11% density snow. Total forecasted accumulations are 8-12″ (20-30cm) for today and another 8-12″ tonight. Winds today will be from the SE, slowly shifting to the E and decreasing slightly. This puts a lot of our avalanche terrain on the windward side of the mountain. Therefore windloading today will be kept down somewhat, but cross loading of N-facing slopes should be expected. Examples include Dodge’s, Hillman’s, and Left in Tuckerman and Escape Hatch, South, and Odell in Huntington. I also think Pinnacle will become loaded due to the eddy effect under the rock buttress. Since they’re starting with better baseline stability, these areas will be playing catch-up to the other areas that are starting with more instability. Despite unfavorable wind directions, these areas facing into the wind will still receive additional snow load and will be increasing in avalanche hazard through the day. We are expecting a slight lull in the snowfall rate later this morning and early afternoon, but by the end of the afternoon rates should pick up again. I suspect a lot of tonight’s forecasted total will fall before this avalanche forecast expires, so I want to be clear that I’m basing today’s rating on where I see the avalanche danger for the daylight hours, sometime overnight the avalanche danger will likely exceed today’s rating.

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 8:30a.m. March 19, 2013. 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

2013-03-19 Printable

Avalanche Advisory for Monday 3-18-2013

This advisory expires at 12:00 midnight tonight.

Tuckerman Ravine has MODERATE and LOW avalanche danger. Lobster Claw, Right Gully, Sluice, the Lip, Center Bowl, and Chute all 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 in those locations.

Huntington Ravine has LOW avalanche danger. Natural and human triggered avalanches are unlikely in all forecast areas in Huntington Ravine. Watch for unstable snow in isolated terrain features.

Yesterday’s high winds moved around the relatively low density snow that had been deposited by recent storms. The areas rated Low were predominately scoured by the wind and Moderate areas developed windslab. Good visibility and light wind will allow excellent conditions for assessing the snow today as you travel around the mountain and temperatures will warm as winds shift to the southwest.

Field observations this morning revealed the degree to which scouring occurred in Huntington Ravine.  You might never know we received 16.2” (41cm) of snow since Thursday by looking into the ravines. Crown lines and debris from natural avalanches that occurred over the last several days were, by and large, erased by winds blowing steadily out of the NW in the 60 mile per hour (100kph) range with gusts over 80mph (130kph). Winds blowing this long at that velocity reduce the fresh snow into smaller particles which pack more easily and form stronger bonds than when they exist in the larger, original forms. That said, I would still be on the lookout for places in areas forecasted at Low where the snow may have formed pillows behind lee features.  The wind was not as strong as it can be here so the scouring did not completely eliminate the hazard.  In Central Gully, for instance, near the final choke point near the upper rock band, a smooth pillow of snow would command my attention if I were climbing it today.  I’d also dig around in other areas to be sure that I wasn’t standing on a larger surface of windslab with a weaker layer way down near the ice crust.

Tuckerman Ravine looks as it often does after a windy period. The upper start zones in the Moderate rated areas are blown into hard, textured sastrugi while softer smoother and possibly sensitive wind slabs grace the midsection. This is particularly true of Right Gully, the Sluice and the Lip where large, smooth pillows exist. An experienced party exercising solid avalanche travel and assessment skills might be find decent riding in the mid-section of Lobster Claw or Right Gully though it will be limited by scoured hard surfaces above and below. The Lip through Center Bowl and into Chute may also harbor softer snow, though the hazards of traveling in these sections are greater and more difficult to mitigate. Left Gully and Hillman’s Highway have pockets of wind slab to avoid or assess as well.

Overall, a nice day to be out and about during this calm before the storm. We will be making field observations today in anticipation of a significant snow storm starting this evening.

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 9:00a.m. March 18, 2013. A new advisory will be issued tomorrow.

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

2013-03-18 Printable

Avalanche Advisory for March 17, 2013

This advisory expires at midnight tonight.

Tuckerman Ravine has CONSIDERABLE avalanche danger. Natural avalanches are possible and human triggered avalanches likely. All forecast areas are rated Considerable except for Hillmans Highway and the Little Headwall which have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Thin ice covers areas of the drainage in the Little Headwall.

Huntington Ravine has CONSIDERABLE avalanche danger. Natural avalanches are possible and human triggered avalanches are likely in all forecast areas except for the Escape Hatch which has Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible in that location.

Last night, cold temperatures and light to moderate winds have allowed very little sintering or strengthening to occur in our snowpack.  Currently our snowpack consists of 3 main layers to be concerned about. Since our snowpack was reset by rain, a windslab developed with Thursday’s 7.2” of new snow sitting on weak loose snow then gained more layers of slab from yesterday’s 7.3” of new snow. No small amount of that 14.5” is still available for wind transport today as winds ramp up to the highest speed they’ve blown for the last 48 hours. Add up the increasing wind speed and previous weak layers and the sum is a challenging and potentially dangerous day to move through or under avalanche start zones. While existing windslabs merit a moderate rating in many areas this morning due to being resistant to natural triggers, this will change through the day.  Developing windslabs will push the likelihood of natural avalanches to possible through the day and the probability of human triggered avalanches will increase right along with it.

For those of you interested in applying your avalanche travel techniques and snow assessment skills gained through years of experience and formal training, today will be an easy day to provoke the avalanche dragon. Bear in mind that the dragon, which may appear to be a relatively harmless at first glance, may grow into a more sizable and threatening beast as it moves downslope and gathers readily available snow. If it steps down all the way to the rain crust, you’ll need more than a lucky charm to keep you safe. Thursday’s windslab was really firm in places which could provide a false sense of security due to the lack of deep boot or ski penetration.  Today’s windslab may give you similar feedback so don’t neglect to dig down when making assessments to be certain that the slab’s strength isn’t hiding a weak interface beneath. These windslabs have a way of bridging across terrain features and resisting fracture, potentially luring you into more exposed positions. As a wizened ski patroller from a Utah ski area once said, “Windslabs can be really strong, until they aren’t. And that’s when your problems start.”

Expect elevated avalanche danger today and a wide variety of snow surfaces to travel on.  Active drifting, ground blizzards, cold temperatures, frozen and camouflaged “postholes”, and slick old surfaces will make above treeline travel a real challenge 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 8:48a.m. March 17, 2013. A new advisory will be issued tomorrow.

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

2013-03-17 Printer friendly