Avalanche Advisory for December 26, 2014

Tuckerman and Huntington Ravines have LOW avalanche danger.  Natural and human triggered avalanches are unlikely except in isolated terrain features.

 AVALANCHE PROBLEMS: The potential for isolated areas of Wind slab is the problem to have eyes open for today.  Some scant snow yesterday and some isolated upslope snow showers today may be enough for high W winds to create thin pockets protected behind some terrain features.  This should be a remote issue. The dominate snow personality right now has been created by the recent rain and thaw event which is hitting the reset button in our mountain snowpack.  The saturated snow has been re-freezing deeper as overnight cold temperatures and extreme wind remove heat from the surface down. This is quickly making any older issues and problems that could have been categorized as persistent, moot.  Place your focus on newly developing instabilities that may occur on top of the crust during upcoming precipitation events.
WEATHER: Yesterday, very high winds pummeled the mountains as the front barreled through the region during Christmas morning.  Winds over 100mph (160kph) were common and the summit recorded a peak of 109mph (175kph) which made human outdoor observations difficult.  Nevertheless, the summit crew muscled the precipitation can back for melting and recorded 0.4″ of new snow yesterday, although they noted accurate collections were difficult. Very high winds will continue today, perhaps gusting to 110mph (176kph), along with some additional upslope snow.  Temperatures may rise a bit from the current of 14F (-10C), but not much.  Expect above treeline travel to be beyond difficult, to say extreme seems cliche, but it really describes it pretty well. We know you want to use that newly unwrapped winter parka in the alpine zone, but give it one more day.  Expect brutalizing winds to make it very difficult to deal with both icy surfaces and jumbled rocks, whether you’re on foot or crawling. One small problem could snowball into a desperate scenario when winds get to these levels.

SNOWPACK:  Well, the snow geek party is over for those inclined towards snow structure and crystal study. As the rain drains through the snowpack and and recent heat dissipates, the interesting layers (in 52.5″ total snowfall) from this month will be more or less pinned down by solid bonds leaving us an isothermal snowpack to start the new year. In the meantime, as winds lay down, enjoy the firm snow on the steep approach to climbs, but for goodness sake, don’t trip. The current icy snow surface will lend itself more to skeleton or luge racing than arresting a fall with an axe. Packed trails will demand micro-spikes and maybe a trekking pole or two but don’t forget that crampons are much more secure, both on your boot and on the ice, and may be needed on your chosen objective. Rain water and snow melt will most likely continue to flow in deeper channels of steep gullies so beware of increasing hydraulic pressure behind ice dams. On days like today, it is not unusual to see bloody paw prints on the trail so consider your dog’s pads when hiking on the chopped up, icy surface.

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. December 26, 2014. A new advisory will be issued tomorrow.

Chris Joosen/Frank Carus, Snow Rangers
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2014-12-26 print friendly

Avalanche Advisory for Thursday, December 25, 2014

This advisory expires tonight at 12:00 midnight.

Tuckerman and Huntington Ravines have Considerable avalanche danger today. Natural avalanches are possible and human triggered avalanches are likely. Dangerous avalanche conditions exist and conservative decision making is essential.

AVALANCHE PROBLEM: Wet Slabs are the #1 avalanche problem today.  Record breaking heat coupled with rain continues to saturate our snowpack with free water, creating wet slabs of varying thickness depending on location.  A distant #2, is the potential for some wind slab to develop as the front moves through.  This will turn rain to snow, adding up to 1-3″ (2.5-7.5cm) later this afternoon.  If this accumulation occurs this will be a late day issue.

WEATHER: Forecasts had difficulty with the precipitation amounts over the last 24 hours, as actual rain accumulations came in short of expectations.  As of midnight, the summit and Hermit Lake picked up about 0.7″ (1.8cm) of water during the previous 24 hours, with the general region getting a bit less.  Rain is expected to continue for a little longer before transitioning to snow as the frontal freight train draws cold air into the mountains.  1-3″ (2.5-7.5cm) of snow is expected, associated with a building wind from the West, smashing the 100mph (160kph) mark gusting over 120mph (192kph) late in the day. Temperatures peaked very late last night at 44F, crushing the previous daily high record for the Mount Washington summit.  Since then, the mercury has steadily been falling which will occur more rapidly as the front moves through this morning.   The Ravines are sitting in a mid-elevational warm band in the high 40’sF, trapped between the colder air above and below.  This will likely continue for a while this morning until mixing becomes more substantial with higher wind speeds.

SNOWPACK:  We feel very fortunate that rain totals did not match the earlier predictions of up to 4 times the actual observations.  That said, we are still dealing with a wet snowpack due to both the falling intermittent rain, as well as the melting snow already on the ground. Natural avalanches will continue to be possible due to wet slabs particularly during the first half of the day.   As the moisture moves out, temperatures will fall slowly, decreasing the potential for natural wet slab avalanches.  As this occurs, the water draining rate will exceed the melt rate and the wet surfaces will begin to refreeze, helping stability.  I would expect off trail travel to be arduous and slow because of the isothermal snowpack, inducing very deep boot penetration in most locations.  Climbers should expect the development of ice dam hazards particularly in the Huntington gullies and near ice bulges of the Tuckerman Headwall. This hydraulic pressure can release explosively with a tool placement as refreezing dams up water flow.

As the day progresses wet slab concerns will dissipate, but new thin dry slab concerns will be something to keep in mind.  Up to 3″ of new snow is forecasted which could add up to isolated problems created by a building W wind.  Based on the high velocities, look for pockets behind terrain features sheltered from the anticipated high winds. Extreme velocities are expected to build, gusting towards 130mph on the Washington summit late today.  Maximum winds should hit the highest mark yet for 2014. As high pressure moves in weather will improve over the next several days, but expect very hard surface conditions to exist.  The consequences of a slip and fall will likely be….. terminal velocity.  We’ll discuss more of this tomorrow.

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. December 25, 2014. 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

2014-12-25

Avalanche Advisory for Wednesday, December 24, 2014

This advisory expires tonight at 12:00 midnight.

Tuckerman and Huntington Ravines will have HIGH avalanche danger today. Natural avalanches are likely and human triggered avalanches are very likely. Very dangerous avalanche conditions exist and travel in avalanche terrain is not recommended which includes runout paths.

AVALANCHE PROBLEM: Wet Slabs are the main avalanche problem today.  Several inches of new snow fell yesterday morning which has since transitioned to light rain, freezing rain and drizzle in the higher terrain.  Heavy rain today will rapidly increase instability pushing a number of slabs of varying density to their limit of strength causing some to fail. This will transition several problems to a singular wet slab issue. Expect natural wet slabs today.

WEATHER: The liquid gauntlet is about to begin.  A tropical system is setting it’s mass on the region expected to bring at least 1.5″ of rain to the mountains, much of it falling heavy at times.  Actual forecasted amounts (QPF) have been difficult due to the digital models having a history of trouble with this type of event.  Human forecasters are adding up to another inch to the potential amount and even more in isolated upsloping areas.  This makes the potential liquid window pretty large at 1.5″ to give or take 3″ over the next 24-30 hours.  Another question is wind speeds over the next 48 hours.  They will get ferocious, but forecasts differ on their level of violence.  Today we could see winds exceeding hurricane force on the higher summits gusting towards 90mph.  This upward moving trend will continue tonight, tomorrow and into Thursday evening when some meteorologists are discussing winds gusting to 140mph (224kph)!  Generally expect travel in alpine zones to be particularly horrific as temperatures drop tomorrow and the front moves in through the day.  Where the uncertainty stops is the question of precipitation type today.  The summit of Washington will be crawling towards its daily record with forecasted temperatures in the low 40’sF.  The mercury is anticipated to drift back below freezing after daylight tomorrow morning, changing precipitation back to snow.  Temperatures will continue to fall into the teensF after dark tomorrow night.

SNOWPACK: Typically the snowpack discussion is the longest, but it takes a backseat to the weather today.  This is because issues will become very clear over the next several hours leaving little room for doubt.  Heavy rain intensity rates on a variety of slab densities and thickness will move the Ravines from a current Considerable rating at 730am to the forecasted High avalanche danger.  Natural avalanches will be likely due to wet slab development.  Rain adds weight, melts bonds decreasing slab strength and can lubricate impermeable or semi-impermeable layers such as buried water ice or crusts.  Will every slope naturally avalanche? No.  However a variety of paths criss-cross and the potential for some stream blow outs from under snow water flows such as in Tuckerman’s Lip or Sluice, and Huntington’s narrow gullies, is possible. Therefore, a prudent call is to stay out of avalanche terrain.

Based on the rain and extreme wind forecast a multi day Holiday alpine terrain trip starting this morning would be a horrendous idea. Looks like we’re generally getting a Holiday stocking of coal today, but we’ll talk about a few presents of whiteness in the advisory tomorrow.

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 7:50 a.m. December 24, 2014. 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

2014-12-24

Avalanche Advisory for Tuesday, December 23, 2014

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Considerable and Moderate avalanche danger. The Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway have Considerable danger. Natural avalanches are possible and human triggered avalanches are likely. Cautious route finding and conservative decision making are essential. The Lobster Claw and Right Gully have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. The Lower Snowfields and Little Headwall remain Not Posted due a lack of snow in these locations.

All forecast areas of Huntington Ravine have Considerable danger. Dangerous avalanche conditions exist. Natural avalanches are possible and human triggered avalanches are likely. Conservative decision making is essential.

AVALANCHE PROBLEM: You can take your pick of avalanche problems today. We’re looking at the potential for storm slabs, wet slabs, and/or wet loose avalanches today. These issues are coming as a result of new snow this morning which will likely transition to rain or freezing rain late today. Prior to today’s weather, we had been monitoring old wind slabs. These may become active again as the incoming weather system works to saturate the snowpack with liquid water. Keep this in mind, but for today you should focus your attention on the more immediate problems of new slab development and rain.

WEATHER: As of 8am, about 3″ (7.5cm) of new snow has fallen at Hermit Lake with slightly lower accumulations at Pinkham and the summit of Mt. Washington. The weather forecasters are calling for precipitation to change over to a mixed bag or freezing rain later today. In the ravines, the change is forecast to take place in the late afternoon or early evening. Until this happens, you should be expecting fresh snow falling on S or SW winds in the 25-40mph range (40-65kph). Temperatures will continue to rise through the night and into tomorrow.

The storm system that will be building over the next couple days is a significant one. If the worst-case scenarios play out, we may see upwards of 4″ of rain in favored upslope areas such as North Conway before Thursday morning. Needless to say, this is not a good situation for the snowpack anywhere in the North Country. Be sure to watch the avalanche advisory and weather forecasts carefully if you are planning to be out in the mountains over the next couple days.

SNOWPACK: With new snow falling on southerly winds, you should expect to see the most wind loading and slab development taking place in areas such as Hillman’s or Left Gully in Tuckerman and South and Odell in Huntington. Cross-loading will take place on slopes with a more easterly component, such as the Chute, Center Bowl, Pinnacle, and Central Gullies. All of these locations are prime candidates for avalanche activity to take place. On the northerly gullies of Huntington I would caution you to be aware of the potential for dry or wet loose snow avalanches, especially late in the day. Similar aspects in Tuckerman (i.e. Lobster Claw and Right Gully) are a lower concern due to their thin snow cover, as well as their aspect and lower slope angle.

There are a lot of variables at play today, such as snow totals, timing of the snow-rain transition, temperatures, etc. Each has its own influence on the hazard you’ll face if you’re in avalanche terrain. You’ll do well to focus on the fundamentals. New snow, winds at a favorable direction and speed for loading, and a change to rain or mixed precip should all be commanding your attention and influencing your decision making 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 8:25 a.m. December 23, 2014. 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

2014-12-23

Avalanche Advisory for December 22, 2014

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has MODERATE and LOW avalanche danger. The Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully to identify heightened avalanche conditions and features of concern. All other forecast areas have Low avalanche danger where natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

Huntington Ravine has MODERATE and LOW avalanche danger. North, Damnation, Yale, and Central have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate the snow and terrain carefully. Pinnacle, Odell, South Gully, and the Escape Hatch have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

AVALANCHE PROBLEM: Wind slab from last Thursday’s wind event continue to be our primary concern. Piles of sluff or point release debris from steep terrain run a very close second. Though both types of slab offer moderate to good stability, a weak layer exists within reach of a human trigger on the surface in enough places in our Ravines to maintain the Moderate rating. Continue to evaluate snow carefully when moving around our terrain. Avalanches on this wind slab could be on the large side in Central Gully, and in the hangfire in parts of the Lip, Center Bowl and Chute with other smaller areas remaining a problem in many other areas such as the top of Yale and Damnation.

WEATHER: Light winds will continue today, though clouds and fog will challenge visual assessment of our snow surfaces. While not frigid, or even very cold by Mount Washington standards, overnight temperatures have been cold enough the last two nights to preserve the weaker layers in our snowpack which are creating our current instability. Calm winds, cloud cover and a high near 20F today won’t change much about the snowpack or avalanche conditions again today and will help preserve our weak layers for Wednesday’s rain on snow event.

SNOWPACK: Jeff and I split up with volunteers yesterday and made some observations in Huntington and Tuckerman yesterday. The changes that 98 mph winds last Thursday brought to the remaining snow was immediately obvious while climbing around on slopes beneath the steeper parts of gullies. Scouring action left a widely variable surface of refrozen wet snow and ice crust but with pencil hard wind slab the predominate surface.  Our snowpack is pretty shallow, given our position on the calendar, so depth hoar and collapsing snow over rocks, holes and shrubs added to the fun. Stability tests confirmed suspicions that pencil hard wind slabs are still potentially active with moderate results on clean (Q2) shears on multiple layers with the upper 50cm. One ECT did not propagate, but I wouldn’t bank on this result in all areas due to the variability in depth and strength of the weak layers. Most disconcerting is the interface between Thursday’s wind slab and the refrozen wet snow crust. This layer is widely variable in depth and in many places has avalanched already (beneath the choke in Chute, low in Lip) or has been scoured out by the wind (top of Left Gully). In some places this layer is likely nearer the surface and here the overlying pencil hard wind slab may be thin enough to crack and avalanche. Central Gully, the mid-section of Chute and the bowl-like section of Sluice are areas I would avoid due to this issue and the expanse of wind slab. I would approach other areas like the top pitches of Yale, Damnation and Pinnacle cautiously and take the time to protect myself and my belayer. Sluff piles which have reloaded the bed surface in many areas are best avoided and left for Wednesday’s rain to clean out. Last Saturday allowed for sunshine and warmer temperatures in the Ravines but solar gain in the snowpack was limited to very particular locations with the most direct southerly aspect near shrubs and rocks. Lately, night-time clear skies and calm winds have treated snow geeks to a really nice surface hoar display with frost feathers up to 10mm in places.

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 7:45 a.m. December 22, 2014. 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

2014-12-22 print friendly

Avalanche Advisory for Sunday, December 21, 2014

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has MODERATE and LOW avalanche danger. The Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully to identify heightened avalanche conditions and features of concern. All other forecast areas have Low avalanche danger where natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

Huntington Ravine has MODERATE and LOW avalanche danger. North, Damnation, Yale, Central and Pinnacle have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate the snow and terrain carefully. Odell, South Gully, and the Escape Hatch have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

AVALANCHE PROBLEM: The wind slab leftover from Thursday’s loading event is the primary threat today. This includes deeper sluff piles that have the tendency to act as areas of deeper slab and can harbor instabilities while more shallow locations move slowly toward stabilization.

WEATHER: In addition to being National Look on the Bright Side Day, today is the winter solstice, the first day of winter, and the shortest day of the year. With light winds and seasonable winter temperatures, there will be little weather-related movement in our avalanche danger either toward stability or instability. Yesterday was warm and sunny so there was likely some stabilization taking place in the upper layers of the snowpack. However, the sluff piles and slabs that we have concerns about tend to be deeper than the extent to which solar gain and warm temperature would have had a strong stabilizing effect.

SNOWPACK: Despite this year’s winter getting off to a good start, we are still looking at a very early season snowpack. In the ravines this is marked by intense spatial variability, broken and discontinuous snowfields, and large expanses of exposed rocks that should make you think about your travel route and its potential consequences in the event of a slide or fall. In Thursday’s avalanche cycle, multiple avalanches occurred in a wide variety of locations. Some were well outside of the “normal” avalanche paths, e.g. in Huntington to the east of North Gully and a small snow slope high above Diagonal. This should raise your hackles about any small pocket that didn’t release.

Solar gain and warmth yesterday likely had stabilizing effect, especially on slopes with a southerly aspect. However, we are reluctant to lower the ratings in many locations due to the depth of instabilities, particularly in sluff piles, may have prevented the solar energy from truly eliminating the weaknesses. There is a good chance you could be traveling on snow that has good stability, only to very quickly move into deeper slab with worse stability. This is where your ability to read the terrain and evaluate the snow becomes critical.

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 8:00 a.m. December 21, 2014. 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

2014-12-21

Avalanche Advisory for Saturday, December 20, 2014

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has MODERATE and LOW avalanche danger. The Sluice, Lip, Center Bowl, Chute and Left Gully have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate the snow and terrain carefully to identify heightened avalanche conditions and features of concern. All other forecast areas have Low avalanche danger where natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

Huntington Ravine has MODERATE and LOW avalanche danger. North, Damnation, Yale, Central and Pinnacle have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate the snow and terrain carefully to identify heightened avalanche conditions and features of concern. Odell, South and the Escape Hatch have Low avalanche danger where natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

AVALANCHE PROBLEM: Wind slab is our primary avalanche concern today. Thursday’s snow and loading winds that created new slabs continue to be our #1 issue.  A number of these slabs naturally avalanched on Thursday and partially reloaded that evening. The reloaded areas and slabs that did not avalanche are now about 30-36 hours old and we have not received new appreciable loading since winds died off late Thursday night. These slabs vary tremendously in depth, weakness, and size. Expect a constant changing condition and stability of the snowpack.

WEATHER: Yesterday’s low winds and moderately cool temperatures will continue this weekend becoming even more comfortable over the next 48hours.  Clear skies today may see a bit of clouds according to forecasts, but the low wind speeds falling to 10mph (16kph) and temperatures between 25-27F (-4 to -3C) degrees will make it quite pleasant to be sporting in the mountains. On Sunday it won’t be quite as nice with a slight chance of snow showers, a bit cooler, and winds up to 35mph, but clearly still a reasonable winter day.  This weekend’s weather should not add new avalanche concerns to our present conditions.
SNOWPACK: Frank and I got into Tuckerman yesterday and battled with a shifting cloud deck that pulled the veil back and forth over the terrain.  This gave us some visibility and then took back away.  We were able to see natural avalanche activity results out of the Lip, several locales in the Center Bowl, the Chute and Left Gully.  Some of these areas have reloaded by sluffing from steep terrain above and wind transported snow.  Other areas that were exposed to high NW winds, gusting regularly to 85mph (136kph) and peaking at 98mph (157kph) on Thursday, have been eroded sending crystals down into the trees. You will find an intense amount of variability as you move across the terrain. Expect to find a vast variety of snow stability so it will be important to choose assessment techniques that you can do quickly so you can perform them often.  Do not be happy with just one stability test, the variability in slabs dictates doing assessments frequently. In Tuckerman, we decided there was certainly enough concern to rate some areas at Moderate. With that said, an experienced user with avalanche knowledge should be able to pick out a route that links stable areas and islands of water ice and rock due to clear visual clues and clear sky conditions.  This is true if you are flexible with your route choices as some areas in the Ravine have less concerns to mitigate than others.  Pockets of slab near the Lip, under the Headwall ice, and above the fracture in the Chute are a few example of places to avoid.  In Huntington, this can be more difficult because your route choices become more limited in narrow gullies.  Again, the visibility today should allow you to spend some time picking out clues that will help your route decisions.  Certainly be prepared with rock and ice gear and lace up areas if you find yourself in unstable snow that you didn’t avoid through your pre-planning.  If you look closely you will see avalanche debris in many places and we believe most of the Huntington gullies sluffed or slab avalanched during this last cycle. As mentioned yesterday, be cautious of the bluebird day mentality. Beautiful days often find us enjoying our experience so much we avoid looking for hazards.  This leads us to fall into heuristic traps and drawing us in deeper into risk than we would if we were focused.

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 8:19 a.m. December 20, 2014. 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

2014-12-20

Avalanche Advisory for Friday, December 19, 2014

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. The Sluice, Lip, Center Bowl, Chute and Left Gully have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Careful snowpack evaluation, cautious route-finding and conservative decision making are essential. All other forecast areas have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger. Central, Pinnacle, and Odell Gullies have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Careful snowpack evaluation, cautious route-finding and conservative decision making are essential. All other forecast areas have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible.

AVALANCHE PROBLEM: Wind slab is our primary avalanche concern again today. New snow and increasing wind speeds yesterday created hard wind slab in many areas. Where these wind slabs exist, they are likely to be hard, fairly thick and capable of propagating a crack on a slope above you. In other areas more sheltered from the strongest NW winds, softer Storm Slabs mixed with the wind slabs may also present a problem. Travel very carefully to avoid these unstable slabs as well as the paths and terrain traps beneath them.

WEATHER: Visibility today, though improving, will be hit or miss as remnants of this last low pressure system clear out. Temperatures will rise to around 20F (-7C) with light to moderate wind from the north in the 25-35 mph (40-55 kph) range. Gusts, potentially to 45 mph (75 kph), will keep things cool but should allow for a decent summit day. Don’t forget that we are approaching the shortest day of the year with around 9 hours of daylight with which to get things done. Sunset is at 4:07 pm.
SNOWPACK: Yesterday snowfall rates continued to impress us adding 6+” (15+cm) by noon, totaling 16.6″ (42cm) for the storm event.  Wind speed increased from the NW during the early morning hours on Thursday and ramped up over several hours moving snow from the alpine zone, mixed with new snowfall, into aspects with an eastern component.  Undoubtedly some crossloading occurred on slopes perpendicular to the prevailing NW direction.  We believe new slab density increased as wind speeds climbed through daylight peaking around 6pm creating an unstable snowpack with dense over lighter slabs.  High volumes of snow were transported into most forecast areas creating a peak instability more than likely close to the twilight hours. Velocities dropped all night to a current of 18mph.  As winds fell back down below about 50mph around 10pm, the vast majority of loading shut down.  This information has us less focused on natural avalanche activity, but based on the cold temperatures and short duration for natural settlement humans have a possible to likely chance of triggering slab avalanches. Expect slab densities and instability to change depending on whether or not slopes were exposed to high NW winds. You may start ascending on heavily wind scouring locations down low and then move into much lighter and unstable slabs as you approach protected terrain features.

Both Ravines are still encapsulated in clouds so we are unable to verify where avalanche activity occurred or what forecast areas received more snow than others. However, historically the locations posted at Considerable today receive the most volume, harbor higher slab instabilities, and require more caution from weather events similar to the last 48 hours.  We expect clouds to begin clearing soon allowing us to get into the terrain for new data collection that will get posted in the Weekend Update late in the afternoon.  In the mean time expect cold slabs to be unstable and hold the ability to propagate a fracture.  With bluebird days approaching with light winds watch yourself and the heuristic traps we can fall into when we are basking in what appears to be an “unbelievably awesome” day. Anticipate lingering instability in the high mountains this weekend.

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 7:50 a.m. December 19, 2014. A new advisory will be issued tomorrow.

Frank Carus/Christopher Joosen, Snow Rangers
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2014-12-19

 

Avalanche Advisory for Thursday, December 18, 2014

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has HIGH and CONSIDERABLE avalanche danger. The Sluice, Lip, Center Bowl, Chute and Left Gully have High avalanche danger.  Very dangerous avalanche conditions exist.  Natural avalanches are likely and human triggered avalanches are very likely. All other forecast areas have Considerable avalanche danger. Dangerous avalanche conditions exist.  Natural avalanches are possible and human triggered avalanches are likely.

Huntington Ravine has HIGH and CONSIDERABLE avalanche danger. Central, Pinnacle, and Odell Gullies have High avalanche danger.  Very dangerous avalanche conditions exist.  Natural avalanches are likely and human triggered avalanches are very likely. All other forecast areas have Considerable avalanche danger. Dangerous avalanche conditions exist.  Natural avalanches are possible and human triggered avalanches are likely

AVALANCHE PROBLEM: Wind Slab today will create widespread avalanche hazard in both ravines. A strong northwest wind will continue to grow in velocity and with it, Wind Slab will grow in size. Areas rated High are likely to avalanche naturally at some point today due to the weak layer, comprised of yesterday’s new snow. Very dangerous avalanche conditions will exist today and travel in avalanche terrain or onto the floor of either Ravine is not recommended. This includes the area around Lunch Rocks, the Tuckerman Ravine trail and the Fan in Huntington Ravine. Our avalanche paths survived the recent warmup and are large enough to generate avalanches which could easily bury and kill a person. Some forecast area avalanche tracks are certainly less developed but are still capable of producing a dangerous avalanche.

WEATHER: Forecasted NW wind with speeds today in the 50 mph range, gusting to 85 mph, will be ideal for loading our slopes and gullies with snow. Snow will taper to snow showers this afternoon and will continue to add to the snow available for wind loading. Visibility will be strongly diminished through most of the day due to this classic weather pattern that frequently comes with the passage of a Low pressure system. Freezing fog will further hamper visibility through the day. Some clearing tomorrow will allow for snowpack assessment, but anticipate elevated avalanche danger tomorrow as well.

SNOWPACK: Yesterday was a good example of how important it is to stay on your toes and make decisions based on new information from Mother Nature.  We had an uneasy feeling about the weather forecasts, hence the discussions about an increasing avalanche danger if weather differs from forecasts.  Sure enough, by 1045 am Wednesday morning between 6-7” (15-18cm) had fallen from a SE direction, more than the entire 24 hour forecast.  As snow continued, adding up to 9.5” (24cm) of 9.9% density by midnight, the avalanche forecast remained accurate because the forecasted wind increase occur remaining in the teens mph.  This is all changing as current weather screams avalanches!  Since midnight snow has continued and is expected to give us another 2-4”, giving the alpine zones about a foot (30cm) for the ramping NW winds to transport.  Overnight NNW wind speeds in the 40’s began to move snow into the ravine, but over the past several hours gusts are into the 60’s from the NW.  Velocities are expected to increase to 80-85 mph today which will move large volumes of snow into eastern aspects.  This is a fairly straight forward, watch out situation.  We expect natural avalanche activity in our forecast areas to be between possible and likely.  Building winds should develop slabs of increasing density over the low density layer from yesterday afternoon.  Slabs will develop with cold snow that fell between temperatures of 25 and 28F Wednesday morning to the current of 12F.  Certainly a day to give the terrain a wide berth. We’ll stay out of the terrain today, but look forward to assessing conditions tomorrow if the hazard decreases for a good Weekend update Friday afternoon on www.mountwashingtonavalanchecenter.org

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 7:45 a.m. December 18, 2014. A new advisory will be issued tomorrow.

Frank Carus/Christopher Joosen, Snow Rangers
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2014-12-18

Avalanche Advisory for Wednesday, December 17, 2014

This advisory expires tonight at 12:00 midnight.

All forecast areas of Tuckerman and Huntington Ravine currently have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features which may be capable of producing small avalanches.

AVALANCHE PROBLEM: Today’s avalanche problem #1 will be small Wet Slabs. This will depend greatly on the timing of the temperature drop and if  we receive rain before the forecasted mixed precipitation and snow set it later today.  Problem #2 are the lingering pockets of Wind Slab that have been hanging on in completely shaded gullies that don’t see direct solar effect.  I wouldn’t quite call them persistent, but they are getting a little long in the tooth compared to the secondary wind slab problem with new snow expected today.  The timing and accumulation of new snow is critical and the most important issue to watch today. A rating of Low danger is the most appropriate assignment to both Ravines, but it includes the possibility for unstable snow in isolated terrain features or in extreme terrain. Today will also be dynamic with changes occurring to the snowpack……read on for more insight.

WEATHER: Yesterday witnessed a pretty interesting inversion around the beltline of Mount Washington. As winds shifted to the SW around 3pm the temperature peaked on the summit to just shy of 36F.  The Ravines pushed even higher due to ample sun, but below Hermit Lake in the undercasted clouds it remained below freezing.  As already mentioned today will be dynamic.  A total expected water equivalent (QPF) of 0.4-0.5″ is forecasted by very late tonight.  A wintry mix should transition to snow after lunch time with the mercury drop and continue into Thursday delivering 3-6″ (7.5-15cm) by dawn. Anticipate the potential for some rain early this morning.

SNOWPACK: Yesterday the solar gain continued to drive heating down into the snow pack.  We found the differences of a slight aspect change to be a remarkable player in how deep you could find wet snow.  As you would expect, the S facing slopes were far more gloppy, wet, and harder to deal with when traveling than N facing areas.  Even with fairly warm temperatures close to 40F, areas completely shaded remained cold and could actually harbor some propagation potential.  This threat is minimal, but worthy to remember. As the temperature drops the current snowpack is moving towards strength as free water refreezes from the surface down.  The issue of wet grain depth based on aspect will be a player in the speed of a complete lock up.

The main thing to pay attention to today is exactly what form precipitation takes and when transitions occur.  Forecasts are somewhat conflicting with one showing a frozen mix moving to rain before a late snow change and another showing mixed precipitation moving to snow. Be prepared for a variety of changing forms today.  If we get rain for a period I would be most concerned about the isolated cold pockets of snow that still exist, such as in North gully or perhaps Pinnacle.  The vast majority of areas that have been cooking and settling should accept a bit of liquid with little effect.  The second thing to watch is the timing and accumulation of new snow.  If weather forecasts are realized with snow accumulations becoming more consistent this afternoon expect some new loading late in the day by an increasing NW wind. However, some light new snow is currently falling with the summit temperature of 25F and Hermit Lake at 32F.  If snow continues from this point forward and does not change forms, which is contradictory to the forecast, I expect some thin new slabs to develop hedging us to a Moderate rating this afternoon. I mention this because it is a possibility that we may see a changing avalanche danger with weather differing from the expected forecast.  Tomorrow anticipate danger ratings and the avalanche forecast to increase.

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 7:50 a.m. December 17, 2014. 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

2014-12-17