Avalanche Advisory for Sunday, 2-19-2012

Expires 12:00 midnight, February 19, 2012

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

Huntington Ravine has MODERATE and LOW avalanche danger.  North, Damnation, Pinnacle, Odell, and the Escape Hatch have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features. Yale, Central, and South gullies have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.

Five inches (13cm) of new snow in the past three days has done a lot to change the appearance of the ravines since the last time they were basking in sunlight on Thursday. What had been a mix of wind effected slabs, ski and boot tracks, and crusts is now covered in a smooth blanket of creamy white windslab. This is what winter up here is supposed to be like. The weather today is going to play a role in the avalanche danger rating. Currently winds are blowing from the NW at 55-65mph (89-105kph), and blowing snow is coming in from above the ravines. This active loading is preventing me from dropping the danger rating in the Sluice through the Chute in Tuckerman. More than a couple times, I’ve seen bluebird days just like this where low drifting snow into the Lip and Bowl is sufficient to trigger an avalanche. As high pressure builds in, winds will decrease in velocity. This may shut down wind loading altogether and eliminate the potential for naturally-triggered avalanches, which in turn would bring the avalanche danger down to Moderate. The snow that will be leftover will still be worthy of careful stability evaluation if you are looking to get out onto the slopes. This morning there are crown lines visible from recent avalanches in the Duchess and the Center Bowl. These should be considered “bulls-eye” data that indicate the presence of unstable snow. The crown in the Bowl has mostly reloaded and may not be visible for much longer if the wind loading persists. As with the past few days, the primary threat is the newly developed slabs from the recent snow.

Some areas of Tuckerman offer better options than others for traveling through avalanche terrain. Due to the low snow totals this season, the terrain on the northern side, i.e. Right Gully and Lobster Claw, has more discontinuous snowfields and more islands of safety that you can link together. Areas such as Hillman’s and Left Gully will make it more difficult to avoid exposure to the avalanche paths. Keep in mind there are lots of human factors at play today. It’s the first sunny day after a snowfall, it’s a holiday weekend, and the snow looks like it would be a joy to ski or ride…all these mean you’ll need to be heads up not only for yourself, but for what others are doing nearby.

Huntington has a mix of Low and Moderate danger. In those locations rated Low, expect to find small pockets of unstable new snow. Areas such as above the ice in Odell, near the top of Pinnacle, and in climbers’ right side of the Escape Hatch are examples of where you might find these. The locations rated Moderate have larger snowfields that are too big to call “pockets”. Whether the slab you encounter is small or large, you’ll want to evaluate the stability and do your best to avoid traveling through unstable snow. The consequences of even a very small slide in Huntington can be severe.     

Please Remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
  • Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
  • For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.  
  • Posted 8:35am. A new advisory will be issued tomorrow.

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

2012-02-19 Print Friendly

Avalanche Advisory for Saturday 2-18-2012

Expires 12:00 midnight, February 18, 2012

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

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

If you’ve been spending your time down in the valleys over the past two days, you might be wondering why avalanche danger is where it is. After an uncomfortably cold morning in Tuckerman yesterday, I was shocked to drive down into sunny 40F temperatures in Gorham. The past couple of days have been very winter-like up here, and we’ve even received a couple shots of new snow. So far, the snow totals have been 3” at the summit, with another 1-2” forecasted for today. We estimate that roughly the same amount has fallen at lower elevations, but the winds have conspired to prevent us from accurately measuring this snowfall. This has all taken place since early Friday morning, and during this time winds have slowly ramped up from SW 15mph (24kph) to the current WNW 50-60mph range (80-97kph). Today we’ll have a little more snow this morning, followed by a brief break in the weather, and then another snow shower in the afternoon.

With the winds acting as they have been, we have concerns about the potential for both naturally triggered and human triggered avalanches. Both of these concerns are made worse today by the fact that it’s a Saturday on a holiday weekend, and visibility is incredibly poor. Don’t make the mistake of unknowingly being in an avalanche runout path, because you won’t have any indication of what’s going on above you. The areas that are most concerning are in the middle of both Tuckerman and Huntington Ravines. Going to the floor of Tuckerman to “take a look” or hiking around on the fan in Huntington will put you at risk of avalanches from above.

The snowpack prior to the new snow was generally stable in all aspects. South-facing slopes received strong solar gain on Thursday, causing the top layers to moisten and subsequently refreeze. East-facing and north-facing slopes didn’t get this new crust development, but there were some places with an older crust exposed at the surface. The northern gullies in Huntington and Lobster Claw and Right Gully will have the best travel options for avoiding newly deposited slabs, but you should expect any new slabs that did develop to be unstable as they are likely sitting on top of a slick crust.

Please Remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
  • Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
  • For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.  
  • Posted 8:35am. A new advisory will be issued tomorrow.

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

2012-02-18 Print Friendly

Avalanche Advisory for Friday, 2-17-2012

Expires 12:00 midnight, February 17, 2012

Tuckerman Ravine has CONSIDERABLE avalanche danger.  Naturally-triggered avalanches are possible and human-triggered avalanches are likely. The only exception to this is the Lobster Claw, which has Moderate avalanche danger. Naturally-triggered avalanches are unlikely and human-triggered avalanches are possible. The Lower Snowfields and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when conditions warrant.

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

The most important thing we want you to understand today is that avalanche danger will be rising. The later you are out on the mountain, the more likely you are to encounter unstable snow. So far, Mt. Washington has received 1.2” (3cm) of 10% density snow, and it is currently snowing at Hermit Lake. We are expecting an additional 1-3” (2.5-7.5cm) during the day and more coming overnight. Winds are going to be at an ideal speed and direction for transporting the 2-4” of available snow into the ravines today, blowing from the W at 35-50mph (56-80kph) early and ramping up to NW 50-70mph (80-113kph) with higher gusts in the afternoon.

Prior to the onset of new snow last night, both ravines had good stability. We’d been at Low danger for at least a couple days in all forecast areas. Today, the primary threat will be windslabs developing from the new snow and wind combination. Expect areas with a strong easterly aspect to develop instabilities first, followed by the adjacent locations. At some point today, I expect to have naturally-triggered avalanches in Tuckerman. I don’t think it’s enough probability to warrant a High rating, but if I were betting on where avalanches will happen today, the Center Bowl and Lip area is where my money would go. I have little doubt these areas will reach into Considerable territory. Other adjacent areas will also get there, but they’ll take more time as the bed surfaces first need to get smoothed out by early wind loading. In Huntington a similar story is playing out, the strong easterly aspects will rise most quickly, followed by adjacent areas. Central, Pinnacle, and Odell stand out for me as the areas of most concern here. Yale and South won’t be far behind, either. Pay attention to the depth of the new snow in Huntington, and be thinking about what could be developing in the gully up above you.

The winds and the potential for new snow will continue to increase into the night, which will allow slab development to continue as well. At this point, I think it’s safe to say there will be some avalanche danger to contend with if you’re coming to the mountain tomorrow. As we do every Friday, we’ll post an update on the Weekend Update section of our website later this afternoon. Also check back for new photos from yesterday’s field trip to the summit.

Please Remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
  • Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
  • For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.  
  • Posted 8:35am. A new advisory will be issued tomorrow.

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

2012-02-17 Print Friendly

Avalanche Advisory for Thursday, 2-16-2012

Expires 12:00 midnight, February 16, 2012

Tuckerman Ravine and Huntington Ravine have LOW avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features. The Lower Snowfields and Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when conditions warrant.

This morning it is my pleasure to bring you a double dose of good news—or, more precisely, to reiterate the weather forecast put out this morning by our friends on the top of Mt. Washington and to give you more or less the same avalanche forecast that Chris wrote yesterday. Both of these are better than what you might be seeing if you’re looking at a weather forecast for the valleys or southern NH. Let’s get into the stability discussion first. Snow stability in the ravines is generally good. We did receive a dusting of snow since yesterday, but this came without much wind at all and will be insufficient to make any difference to avalanche conditions. Today you’ll have many options for different mountaineering routes around the mountain, so get out an enjoy them. Of course, you should still take proper precautions when traveling through avalanche terrain.

The other bit of good news comes to us from the Mt. Washington Observatory and the National Weather Service. Apparently there is going to be some snow in the mountains late today and overnight. Yeah, I couldn’t believe it when I read it for myself. Snow in February? Amazing. This highly unusual weather event is expected to deliver 2-4” (5-10cm) of snow to the higher terrain of the White Mountains. Ok, please excuse me if that’s too heavy handed with the sarcasm. After only 107 total inches (271cm) of snow since November 1 at the summit, of which only 11” has come in the last two weeks, I’m feeling less than optimistic about the prospects for the rest of the winter. Regardless of how I feel, there is snow coming tonight. This snow will come with winds from the SW shifting to the W and increasing in speeds. On Friday we’ll likely see some lingering upslope snow showers, hopefully accumulating to a couple more inches. Winds will continue to increase in velocity, setting us up for a holiday weekend with avalanche danger greater than where it stands today.

We’ve fielded a lot of questions recently about how conditions are coming along up here. It’s no secret that this has been a very dry winter, with a seemingly excessive number of warm days up high. The slopes of Tuckerman Ravine are snow covered, but there are still lots of exposed rocks and brush. The floor of the ravine has seen very few large avalanches, which is the primary way it fills in with snow. Most of the gullies have also had few avalanches, so their runouts are not very well filled in either. Getting onto the Little Headwall is a nasty bushwhack no matter which way you go about it. Despite the general lack of snow, conditions aren’t too bad. Keep in mind that surface conditions for travel can change greatly from day to day, as can the avalanche danger. One day might be “good” or even “great” conditions, but the following day might be “horrifying.”

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 8:00am. A new advisory will be issued tomorrow.

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

2012-02-16 Print friendly

Avalanche Advisory for Wednesday 2-15-2012

Expires at midnight, Wednesday 2-15-2012

Tuckerman and Huntington Ravines have LOW avalanche danger.  Natural and human triggered avalanches are unlikely except in isolated terrain features. The Lower Snowfields and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when conditions warrant.

 A foreboding sky over the mountains is a bit more bark than bite today as weather forecasts are only calling for some flurries and a potential brief snow shower.  A disorganized system will be shuffling along giving the mountains, clouds and fog across the higher landscape of the White’s through the day.  We aren’t anticipating enough snow to make a difference for snow stability to move any avalanche forecasts above ‘Low’.  As always be ready for the mountains to deliver some weather surprises, such as a shot of snow.  However, no weather information is pointing to getting more than a passing shower or two of light intensity.  As we move into tonight and tomorrow the chance of precipitation will increase.  Thursday night and Friday we have a 70% chance of moisture with the potential of 2-4” (5-10cm) to fall before a clearing weekend.  Overall, it will be a cloudy few days ahead with a bit of precipitation each day.  We are continuing to run the fine line between rain and snow due to temperature expectations near the freezing point at mid mountain elevations so stay tuned.

Expect foot travel to be a mixed bag of staying on top due to hard crusts and steel slab styrofoam, or breaking through the surface down in the trees or in protected lee areas that were protected from high winds earlier in the week.  As mentioned yesterday we are continuing to do some hauling on the Sherburne ski trail with our snowcat due to extremely thin coverage on the Tucks Trail.  Talking to two skiers yesterday the cat tracks are chewing up the ice which actually improved the rugged ski conditions.              

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 8:10a.m. A new advisory will be issued tomorrow.
 

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

2012-02-15 Print Version

 

Avalanche Advisory for Tuesday, 2-14-2012

This advisory expires at midnight, Tuesday 2-14-2012 

Tuckerman and Huntington Ravines have LOW avalanche danger.  Natural and human triggered avalanches are unlikely except in isolated terrain features. The Lower Snowfields and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when conditions warrant.

 After 5 days of very limited snow and high winds we have a generally stable snowpack.  Although there are some isolated pockets to give a second look while you’re traveling in avalanche terrain you will have many good options to enjoy the hills.  Maximum winds of 118 mph yesterday have been the dominate player in beating the slopes into submission, setting up overall hard surface conditions.  A nice day ahead will deliver partly sunny skies and a diminishing wind from the W dropping to 25-40mph (40-65kph).   Later today increasing clouds will begin the chance of snow showers overnight and into tomorrow. These showers are expected to give the high mountains 1-2” (2.5-5cm) by the time they shut down.  The rest of the week ahead will be rather mild and potentially bleak for lovers of winter.   Wednesday, Thursday and Friday all have a chance for moisture with evening temperatures going below freezing at all elevations; and days likely going above freezing, at least in lower avalanche terrain.  We are hoping for the best, but I have to say it, we will be flirting with rain. Valley temperatures will be in the mid forties each day with the high summits in the mid twenties Fahrenheit.  The flipside potential to the rain scenario is picking up a little snow each day as models seem to show a steep temperature gradient between the lowlands and the upper peaks of the Presidentials.  Cross your fingers and be ready for a slight rise in avalanche danger and snow instabilities.

Expect foot travel to be a mixed bag of staying on top due to hard crusts and steel slab styrofoam, or breaking through the surface down in the trees or in protected lee areas that were protected from high winds.  Expect the Sherburne ski trail to be a bit rugged this week with some rain and freezing nights.  In addition, although we put it off as long as we could, we needed to do some supply hauling for all facilities on the mountain, which has forced us onto the ski trail with our snowcat.  We typically wait and travel on the hiking trail but we are so far from being able to do this, due to thin cover, we can no longer hedge our bets.  We picked a grim week with hard conditions so we wouldn’t make much of an impact on skiing quality.  This resupply may occur at random in the near future, but we will always be thinking about the impact on “good skiing” if it actually returns.                              

Please Remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
  • Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
  • For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.  
  • Posted 8:45a.m. A new advisory will be issued tomorrow.
 

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

2012-02-14 Print Version

 

Avalanche Advisory for Monday, 2-13-2012

Expires 12:00 midnight, 2-13-2012 

All forecast areas of Tuckerman Ravine have MODERATE avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible. Please read the discussion below for more information about the danger rating today. The Lower Snowfields and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when conditions warrant.

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

It’s yet another cold windy morning at Hermit Lake with very poor visibility. This is the kind of morning where you’ll benefit from having paid attention to the weather history over the past several days. You won’t get much for visual clues about stability until you are well into avalanche terrain and route finding can be challenging even if you are very familiar with the area. Allow me to take you on a brief tour of the weather from this past weekend. On Saturday, light winds allowed 1.4” of new light density snow to cover the mountain. Then, as night fell, winds slowly ramped up into the 60-80mph range. This pushed a lot of the new snow over into the Cutler River Drainage (i.e. Tuckerman and Huntington) and began to increase the avalanche hazard. Yesterday morning winds decreased slightly as temperatures began to plummet. Then, mid-morning yesterday, winds began to trend slowly upward again. This continues to the present time, with summit winds regularly gusting from the WNW at over 100mph this morning and a peak gust of about 118mph. Temperatures have begun to rebound, but it will take a while to pull up from the lowest temperatures yet this season.

Forecasting today’s avalanche hazard for Huntington is a little easier than for Tuckerman…strong winds have scoured the light density snow out of the gullies, leaving behind predominantly older, more stable snow. You may find an isolated pocket here or there to be careful with, but these will only be in very strongly wind-sheltered locations. Choosing Tuckerman’s avalanche danger rating today was a challenge. I don’t feel as though any of our ratings definitions really nail down exactly how I feel about Tuckerman Ravine. Let’s start with the weather history described above. We know that winds have been working around the clock to move snow into the ravine. During this morning’s increase in velocity, the wind likely picked up snow in all the nooks and crannies that lighter winds left behind. My experiences with this pattern lead me to believe the snow is being loaded into very hard slabs in much of Tuckerman. Some areas may even be getting scoured down to older surfaces (Left Gully is a prime example). The density of the hard slabs will prevent a person’s stress bulb from punching very deeply into the snow, and slab strength can bridge potential weaknesses in all but the thin edges of the slabs. Overall, I believe the potential for human triggered avalanches to be on the lower end. On the other side of the coin, new snow is being loaded into the ravines as I write. This is effectively increasing the load on the snowpack. This additional load could be all that is needed to trigger a nasty hard slab avalanche. I think the possibility for this exists today, though also on the lower end of the probability spectrum. So while a person probably wouldn’t be enough of a force to trigger an avalanche, the weight of additional loading could be. However, the likelihood of this scenario playing out isn’t so great that I’m compelled to call it Considerable danger. Today’s rating of Moderate reflects my overall impression of the avalanche potential in Tuckerman. I’d urge you to be cautious in your choice of route today, since the controls will be in the hands of Mother Nature today. You may not have much say in whether or not avalanches take place, but you certainly have a say in where you travel. 

Please Remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
  • Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
  • For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.  
  • Posted 8:35am. A new advisory will be issued tomorrow.

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

2012-02-13 Print Friendly

Avalanche Advisory for Sunday, 2-12-2012

Expires 12:00 midnight, 2-12-2012

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

Huntington Ravine has MODERATE and LOW avalanche danger. North, Damnation, and Yale have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features. All other forecast areas have Moderate danger. Natural avalanches are unlikely and human triggered avalanches are possible.

With temperatures falling to the lowest we’ve seen this winter, I suspect that traffic on the mountain will be rather light for a weekend day. It’s currently -16F (-27C) at the summit and -3F (-20C) at Hermit Lake. The cooling trend will continue into the overnight hours, ultimately dropping below -20F before temps begin to rebound. To be clear, these temperatures are the actual temperatures, not the wind chill. Winds today will remain strong, blowing from the NW around 55-75mph (88-120kph). Not only will this make the air feel a lot colder than it already is, but it will continue to blow yesterday’s snow from the west side of the mountain over to the east. Come well equipped for cold weather, even if your plan is just to do a fast lap on the icy Sherburne.

Not a whole lot of snow actually fell yesterday. The summit recorded 1.4″ of very light density snow. Down at Hermit Lake we observed about the same amount around mid-afternoon. While it fell, the winds were very light, which allowed a layer of weak snow to blanket the higher elevation terrain, including avalanche starting zones. On top of this light density blanket, increasing wind speeds began to transport the snow over the tops of the ravines. This created an “upside down snowpack” with denser, stronger layering on top of lighter, weaker layers below. Snowpacks such as this are responsible for a lot of the avalanches we have here each season.

Today’s ratings reflect a range of conditions you can find in avalanche terrain. In the Considerable rated areas, the amount of snow loading going on through today combined with the upside down effect lead us to believe natural avalanche activity is possible. The greatest potential for this is in the Lip and Center Bowl area. On the other end of the spectrum, the light density snow had a difficult time sticking to slopes exposed to strong overnight winds. The northern gullies of Huntington may have pockets of unstable snow in isolated lee areas, but the prevailing surface condition here will be stable older snow. Elsewhere in both ravines you will find snow that spans the entire range of the Moderate rating definition. Areas more prone to scouring, such as Hillman’s, Left, and much of Huntington, will have areas of unstable snow too large to call a “pocket” or “isolated terrain feature,” but a lot of the surfaces in these forecast areas will have generally good stability. Due to continued snow loading today, I wouldn’t completely rule out the potential for natural avalanche in these areas, but I believe the likelihood and overall avalanche hazard better fits into the Moderate rating. In Right Gully and the Lobster Claw, the overall lack of snow is keeping  reasonable travel options open despite their being in the direct lee of NW winds. On the climbers’ left side of these gullies is where you’re more likely to find areas of instability. Regardless of where you go, poor visibility will hamper your efforts to make accurate assessments from afar. With the weather being what it is today, you may want to be a little more conservative in your route choices.

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 8:50am. A new advisory will be issued tomorrow.

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

2012-02-12 Print Friendly

Avalanche Advisory for Saturday, 2-11-2012

Expires at Midnight Saturday 2-11-2012

Tuckerman and Huntington Ravines have MODERATE avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible.  The Lower Snowfields and the Little Headwall are not posted due to an overall lack of snow. Forecasts for these locations will begin when conditions warrant.

 Today’s avalanche forecast is mostly based on the expected light snowfall today and an increasing wind.  New snow, which just started over the past hour, is forecasted to give the higher summits 1-2” (2.5-5cm) by later this afternoon.  Light winds this morning from the W will shift to the NW and increase with gusts to 40 mph (65kph) late in the day.   If this weather maker plays out as forecasted, the initial new snow should lay as a thin blanket across the mountain due to the very low wind speeds (8mph/14kph) this morning.  As winds increase light slabs may build over this loose unconsolidated layer that would possibly act as the new weak layer of concern.  Any new thin slabs would most likely be found near the tops of gullies and snow fields, in the strong lee of both ravines, due to the relatively gentle winds for Washington.  For most locations, particularly N and NE facing aspects, this process and concern will take most of the day.   Therefore areas that were posted at Low yesterday, like all of Huntington, will remain there through most of the morning until winds pick up and start moving areas into Moderate danger.  Areas in the lee of WNW and NW winds will have new slab concerns first, with others trailing behind. 

In Tuckerman, high in the Right Gully, Sluice, Lip, and under the Headwall ice will build slabs before areas like Hillman’s Highway.  In Huntington, Yale, Central, Pinnacle, and Odell will develop slabs before South Gully and the Escape Hatch.  This entire issue today all depends once again on EXACTLY how much snow we get and what the winds actually increase to this afternoon.  Our forecaster’s discussion this morning highlighted how just a small amount of differences could substantially change the reality on the ground.  A half an inch (1.25cm) with winds to 30mph (48kph) will be very different from 2.5” (6.25cm) and 45mph (72kph) velocities.  On the low end, areas will struggle to achieve the Moderate rating.  On the upper end, or surpassing the weather forecasts slightly, may push a number of areas to the upper end of the Moderate rating.  Watch the accumulations closely, think ahead to where you might be this afternoon and consider your bail out options.  The slight nuances will make a difference today.  Before these new snow issues came into the picture our last lingering concern yesterday was some slabs in the Chute, Center Bowl and Lip of Tuckerman.  Although these were barely above “Low” we did have some concern for a large impact ripping out a slab deposited from earlier in the week.  This concern exists today with any large sluffs, or perhaps a slab avalanche, which may step down creating a bigger moving mass of snow. 

As this weather system moves out late in the day winds will increase overnight to 70mph (112kph) associated with a drop in the mercury.  Temperatures below zero will start overnight and continue to fall all day on Sunday and into Monday morning.  Expect full on arctic conditions tomorrow with high winds and negative numbers in the teens F (-26C).  Finally, reports from the people who have tried to get into an out of the Little Headwall indicate that the slope itself is reasonably good skiing, but getting in and out of the area makes the experience not a worthwhile endeavor.

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. A new advisory will be issued tomorrow.
 

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

2012-02-11 Print Version

 

Avalanche Advisory for Friday, 2-10-2012

Expires 12:00 midnight, 2-10-2012

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

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

High pressure will stay in control once again today before we get a little break from the sunshine tomorrow. Today’s stability issues are the same ones we’ve been dealing with for a few days now. Over time, changes are taking place within the snowpack. Some of these are leading toward greater stability, and others are exacerbating the weak layer concerns. Exactly where you travel today will play a large role in whether or not you see unstable snow. In many areas of both ravines, snow stability is quite good. These are the areas we’ve rated Low danger for the past couple days. Those areas rated Moderate are currently sitting toward the lower end of the Moderate rating. However, we don’t have enough confidence in their stability to drop them to Low danger. The problem lies in the uppermost layer of crust that is buried beneath surface slabs and can act as a weak layer. The slabs sitting on the surface (i.e., on top of the crust) have a lot of strength, so it then becomes a question of whether or not a person’s impact would be enough to cause a failure of the weak layer. In such a lean snow year, the overall depth of snow is highly variable, as is the depth at which this crust is buried.

In the Sluice and Chute, much of the terrain has good stability. Below the narrows of the Chute and up the climbers’ left side offer good stability. The concerns lie above the narrows in the middle and right side. In the Sluice, you’ll find the most unstable snow tucked up underneath the ice just as the slope begins to steepen. The greatest stability concerns are still centered on the Lip and Center Bowl, in the steepest slopes below the ice. Overall, the crust is buried more deeply here, but there are numerous locations where the spatial variability could put you unknowingly on a thin spot. If you are able to put enough impact on the slab here, you might have a problem. You (or someone else) might also ski right over it without triggering anything. So I’ll remind you of the old adage, “tracks on a slope do not mean it is safe.” All it takes is the right trigger in the right location.

After a few sunny days, there is some weather heading our way for Saturday. Sadly, it’s trending farther away than we want, so not a lot of snow is forecasted. However, you should be expecting snow showers through the day Saturday. On Sunday, expect falling temperatures, increasing winds, and blowing snow. We’ll give you more detail on this in this afternoon’s Weekend Update, which you can find at our website. And finally, reports from the people who have tried to get into an out of the Little Headwall indicate that the slope itself is reasonably good skiing, but getting in and out of the area makes the experience not a worthwhile endeavor.

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 8:20am. A new advisory will be issued tomorrow.

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

2012-02-10 Print Friendly