Avalanche Advisory for Wednesday April 9, 2014

This advisory expires at midnight

Tuckerman and Huntington Ravine have Moderate avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible.

AVALANCHE PROBLEM: New Wind Slabs are the primary avalanche problem today.  Yesterday snow generally ended during the morning followed by a rapid rise in temperature pushing a good deal of avalanche terrain close to 50F in the afternoon.  Following this warm fog the mercury fell with new snow showers beginning overnight, which is forecasted to continue this morning. This is causing new cold dry snow, on a NW wind, to load into slopes with an E facing component, hence the Wind Slab problem.

WEATHER:  The summit recorded 4.1” of snow and frozen forms, melting to 1.22” of water, in the past 24 hours.  Temperatures hit 38F, the 2nd highest mark of the season so far, which did a good job settling new wet snow from yesterday morning. The new snow overnight, coupled with a freefall of the mercury, will continue this morning. Eventually, ambient air temperatures will settle around 10F on the summit with any additional moisture being limited.  NW winds will increase all day gusting over 80mph late in the forecast period.

SNOWPACK:  In the past couple of days the summit has picked up 7.4” of frozen forms melting to 1.66” of water.  Following this dense, wet, mixed accumulation the temperatures soared to around 50F in avalanche terrain Tuesday afternoon.  Falling temperatures last night began the process of locking up this wet blanket by penetrating deeper into warm snow by the hour. Meanwhile, some light snow began intermittently bringing some new cold snow to E facing slopes, thinly covering some of the previous refreezing slabs.  This light snowfall is expected to continue this morning before a clearing trend begins.  The main issue today is any new cold slabs that may be developing in the two ravines.  This concern has caused us to issue today’s rating of Moderate.  There is some uncertainty exactly how this morning will play out due to the amount of light snow yet to come, an increasing wind, thick fog and blowing snow encapsulating the mountain.  A Moderate rating may be a conservative call for some areas, so anticipate hard crust, potentially breakable, to be as much of a safety issue as avalanches today.  Therefore, expect both a falling hazard, of both you and those above you, as well as new snow instabilities.  A likely scenario is hard conditions down low with areas of new snow in the highest strongest lee slopes.

OTHER HAZARDS: A falling hazard on frozen wind swept slopes is a real concern today so as always an ice ax and crampons are required to travel safely.  Also being ready for winter conditions with a temperature of 10F and hurricane force winds.  Despite the calendar, it is not spring in the mountains today.  Quality winter clothing should be part of your repertoire to avoid hypothermia.

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.Posted 7:55a.m. 4-9-2014. 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

2014-04-09 Print

Avalanche Advisory for Tuesday, April 8, 2014

This advisory expires at 12:00 midnight.

Tuckerman and Huntington Ravine have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Natural avalanches are unlikely and human triggered avalanches are possible.

AVALANCHE PROBLEM: Wet Loose Avalanches are the primary threat today. The standard definition of Moderate danger says that naturally triggered avalanches are unlikely. With today’s loose wet problem, this is not the case. Expect rain today to trigger small wet loose avalanches across many different aspects. Steeper slopes will be more susceptible to this problem. The expected size of these allows the danger rating to be Moderate, whereas Considerable is usually the more appropriate rating when naturally triggered avalanches are possible.

If rain falls heavier than we currently are expecting, avalanche danger may rise further due to the threat of wet slab avalanches. You need to be your own weather observer for this one. If you see heavy rain and not so much frozen precipitation today, consider recreating outside of avalanche terrain.

WEATHER: As one former Snow Ranger used to say…today is a good day to be wearing a house. It’s currently 37°F at Pinkham Notch. The summit is several degrees below freezing, and Hermit Lake sits right at the freezing mark. So the upper portions of the mountain are receiving mixed frozen precipitation, at least for now. Temperatures are expected to rise this morning which will bring rain to all elevations. In the afternoon, precipitation will transition from steady to showery. Temperatures will be falling during this time, so we will begin to see snow showers again in the afternoon. Overnight the summit has received a few inches of heavy dense snow and ice pellets. We will need to wait to see how much more falls before a transition to rain showers.

SNOWPACK: The last two days have turned out to offer good snow conditions for skiing and riding. Yesterday’s warm temperatures helped the snowpack continue on its path to being fully isothermal. However, last night the temperatures only slightly dipped below freezing, so there is going to be some refrozen snow grains near the surface but deeper in the snowpack you would likely still find warm moist snow.

Today’s primary avalanche problem stems from rain landing on two different snow layers. The older one fell on Saturday night with strong NW winds which landed on slopes with an easterly or southeasterly component. Much of this has been skied over, so wet slab concerns are minimal in these locations, but the loose snow that remains can still get moving enough to be a concern. The more recent layer is 3” or so of wet snow and sleet that fell overnight and early this morning. Winds were from the SSE, but the wetness of this snow leaves me thinking it’s blanketing all aspects, not only those in the lee of SSE winds.

OTHER HAZARDS: Swollen streams today may increase the hazard of undermined snow. We’re also beginning to think about falling ice as a potential concern.

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.
  • Posted 7:45 a.m. 4-8-2014. 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

2014-04-08 Printable

Avalanche Advisory for Monday, April 7, 2014

This advisory expires at 12:00 midnight.

Tuckerman and Huntington Ravines have LOW avalanche danger today. Natural and human triggered avalanches are unlikely. Look out for small avalanches in isolated areas or extreme terrain.

AVALANCHE PROBLEM: Loose-Wet (aka point release) avalanches due to warming of Saturday night’s thin wind slabs are the most likely avalanche threat today. Wet Slab avalanches are also possible in a few areas where the wind slab is thicker and not cut up by ski traffic, such as in the Chute and Central. Both avalanche types could push you downhill or knock you off your feet but are unlikely to be large enough to bury you. Low avalanche danger does not mean NO avalanche danger.

WEATHER: Sky cover will slowly increase today as a warm front nudges into our area. An inversion last night created a warm band around the 4,000′ level with colder air above and below. Light but increasing winds with continued rising mercury, topping out in the lower 30’s on the summit, will make for a fairly calm day before mixed precipitation begins around dark. The potential for liquid equivalents around 1.5″ will change things tonight. It is likely that a mix of snow, sleet and freezing rain will Zamboni our slopes and gullies overnight.

SNOWPACK: The summit reported 2″ of snow Saturday night which blew into select areas in the Ravines on fairly high winds. While not deep, these softer wind slabs bonded fairly well to the existing refrozen crust. A lot of triggers were on the slopes yesterday with no avalanches resulting. Some of the shadier aspects like the Chute weren’t tested yesterday. I would be cautious today and keep a close eye on temperatures as warming temperatures will soften and weaken the surface wind slabs. It will be another hard-to-call day in terms of snow surface temperatures due to the timing incoming cloud cover. If clouds thicken significantly by mid-day,  surfaces may not warm enough to soften, especially the harder surfaces devoid of the new snowfall like parts of upper Hillman’s and Left Gully. South facing gullies in Huntington were mostly devoid of new snow yesterday after a good scouring by Saturday night 90 mph wind but pockets probably remain in Central, Pinnacle and Odell.

OTHER HAZARDS: Icy, refrozen snow on higher and steeper terrain can limit penetration of boots or skis. Crampons and an ice axe are recommended for travel on steep slopes. Micro-spikes and other creeper style traction devices may be helpful on some lower angle trails, but they do not provide the security of crampons. Be prepared to handle steep, firm snow and fast, icy surfaces.

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.
  • Posted 7:45 a.m. 4-7-2014. 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

2014-04-07 print friendly

Avalanche Advisory for Sunday, April 6, 2014

This advisory expires at 12:00 midnight.

Tuckerman Ravine has Moderate and Low avalanche danger today. The Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Natural avalanches are unlikely and human triggered avalanches are possible.

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

AVALANCHE PROBLEM: Wind slab will be forming today in a variety of locations. These are developing due to yesterday’s snow and strong winds, and have the potential to become larger and more hazardous with additional snowfall today. The Sluice, Lip, and Center Bowl are the areas of greatest concern. Forecast areas rated at Low danger today may have unstable snow in isolated areas. These will most likely be found in pockets that are sheltered from strong NW winds today, including many locations in Huntington.

WEATHER: Forget what the calendar says and don’t make decisions based on what the weather is doing in the valley…today will be a blustery winter day in the mountains. The forecast is calling for clouds and upslope snow through the early part of the day. The Observatory is reporting 2″ (5cm) of new snow as of midnight, but how much more will fall during this period of upslope is a question mark that can’t be answered in advance. Although clearing is expected this afternoon, strong NW winds will keep recently fallen snow blowing sideways through the air and temperatures are unlikely to rise above the freezing mark by much, if at all. If you have your sights set on skiing or riding in Tuckerman, I’d recommend rescheduling for another day based on weather and avalanche potential.

SNOWPACK: Beneath any slab that has formed from recent snow, the surfaces currently are quite crusty and firm. This layer and the snow beneath them have good stability, but make for poor conditions for skiing, or for climbing up steep slopes in your ski or snowboard boots. Protected lee areas are the most likely to have new wind slab on top of the crust. Where slabs have formed more than a couple inches deep, you can expect avalanche potential. The depth, size, and how connected it is to adjacent locations should be initial questions in your stability assessments. Expect these new slabs to be growing during the day, and increasing the hazard. The slopes mentioned above as the areas of greatest concern will be sitting solidly in the Moderate range. Other locations such as Left Gully and Hillman’s may have more options for avoiding unstable snow. Also remember that Low danger does not mean no danger. This is not your typical spring day…respect the danger that even a small isolated pocket of unstable slab can pose to you, your friends, and others on the slope below you.

OTHER HAZARDS: Icy, refrozen snow on higher and steeper terrain will limit penetration of boots or skis. Crampons and an ice axe are recommended for travel on steep slopes. Micro-spikes and other creeper style traction devices may be helpful on some lower angle trails, but they do not provide the security of crampons.

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.
  • Posted 7:40 a.m. 4-6-2014. 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

2014-04-06 Printable

Avalanche Advisory for Saturday, April 5, 2014

This advisory expires at Midnight.

Tuckerman and Huntington Ravines have MODERATE avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully.

AVALANCHE PROBLEMS:  Wet Slab avalanches due to last nights rain and continuing mixed precipitation will remain the number one concern until temperatures drop further this afternoon. Storm Slab and Wind Slab may take over as the primary threat later today as new snow falls with the potential to quickly build slabs in lee areas. 

WEATHER:  An occluded frontal passage continues until later this morning when warm moist air begins to clear out, making way for colder air. Total precipitation amounts are challenging to predict with this occluded front and upslope flow which follows. Afternoon upslope flow will wring out the remaining moisture bringing snow shower activity to the mountain. History has shown upslope snow shower activity can bring enough precipitation to cause a wind and storm slab avalanche problem. Expect reduced visibility most of the day due to fog and mixed precipitation then, summit fog and snow showers. High winds will develop through the day, eventually reaching 50-70 mph in the afternoon and even higher in the evening hours. Temperatures will fall to the mid-teens F (-10C). Wind will shift to the west from the current southwesterly direction. Tomorrow looks to be a much nicer day in the mountains.

SNOWPACK: Yesterday warm temperatures and sunny skies worked their magic on our terrain and yielded a bumper crop of corn snow. Sluff runnels and piles of snow grains are freezing into death cookies as I write. A short inch of snow with a glaze of ice fell after the rain last night at Hermit Lake and has refrozen near the surface. Many areas, particularly sheltered unpacked areas, will be punchy for a while this morning until cold penetrates the surface and reduces postholing problems. Expect horrendous skiing conditions and long sliding fall potential today. Nearby ski trails will be good alternatives until  later in the day when they freeze up. Some new snow may freshen things up on these trails but the extent and timing is pretty uncertain. Rain and melt yesterday may be building hydraulic pressure and causing ice dam issues on ice climbs so stay aware of this hazard if headed up to do a route.

Icy, refrozen snow on higher and steeper terrain will limit penetration of boots or skis. Crampons and an ice axe are recommended for travel on steep slopes. Micro-spikes and other creeper style traction devices may be helpful on some lower angle trails, but they do not provide the security of crampons.  Also be on the lookout for undermined snow bridges and open holes over stream beds. The Harvard Cabin is closed for the season.

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. Posted 8:00 a.m. 4-5-2014. 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

2014-04-05 Print friendly

Weekend update, Corn field edition

Weather. Again looks like a giant mixed bag of winter and spring precipitation for tonight and into Saturday. A few inches of snow, freezing rain and sleet with a low in the 20’s will make for a delightful evening. Saturday morning will bring more snow, sleet and rain with increasing winds but showing signs of clearing as the day wears on, winds will be on the increase, reaching to the 50 mph mark. Winds will continue to increase through the overnight working its way up and over 80 mph, bringing clearing with it later in the day. As usual there’s a lot more detailed information on the internet, so dig around at NWS site and The Observatory’s site for the latest weather forecasts.

Our substantial eastside snow pack is the sixth best since 1968, for snow totals. Left Gully is as wide as I’ve seen it for quite some time, as well as Chute (or some call it hourglass). The Lip is starting to show some wear and tear due to the latest warming trend, even a few sluff runnels starting to show. Right Gully and Lobster Claw have seen a lot of solar gain and traffic over the past week. As the temperature and the sun climb the southern aspects are moving quickly from winter wonderlands to sloppy piles of surplus feed corn. The Sluice ice has passed it prime and is starting its inexorable metamorphosis into teetering blocks of frozen water awaiting their downhill migration. So as we continue into the spring keep your eyes open for hazards above.

If you’ve been staring out the office window all week anxiously awaiting Saturday morning to come harvest the rows of buttery corn on our slopes you might want to keep the combine parked in the barn. If you are pulling out the combine and heading uphill make sure to check the advisory in the morning for more details.

Chris, Jeff, Frank and Joe

Avalanche Advisory for Friday, April 4, 2014

This advisory expires at Midnight.

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

Slopes with south facing aspects have the potential to lose strength starting in the early afternoon hours. The potential for a human triggered avalanche will increase when this happens. Low danger doesn’t mean no danger.

AVALANCHE PROBLEMS: Persistent slab remains the main threat today on south facing aspects. While we are starting out the day with very low avalanche probability due to a strong, refrozen snowpack, the intense April sun could heat surface slabs. Wet slabs could also become a concern today if and when this heating occurs. Sluice and Lip are the slopes with the highest probability and consequences for these problems, with portions of North, Damnation and Yale close behind.

WEATHER:  Light winds on the summit this morning (20 mph) will increase a bit in the afternoon as overcast skies filter in as the next precipitation maker approaches. A temperature inversion exists this morning with Pinkham standing at 19F while the 4300′ temperature is 27F. By sundown, mixed precipitation should begin with the form determined by your elevation. 2-4″ of sleet and snow are forecast for tonight.

SNOWPACK:  Light wind and sun today will compete with cool temperatures in the struggle to soften the snow surface on south facing aspects. Temperatures in the teens to mid-20’s for the past 24 hours kept the snow surface frozen; however, a “greenhouse” effect from high thin clouds coupled with light wind could lead to heating of the snow in the early afternoon hours. Many folks intent on skiing were skunked yesterday by the cold refrozen snow following Monday and Tuesday’s warm-up. I believe the difference today will be overnight temperatures, which were 10 F warmer last night than the previous night, lower windspeeds and the greenhouse effect of high clouds. An approaching warm front will allow filtered  solar radiation to reflect back into the lower atmosphere and nudge temperatures higher. Of course, it will be a very close call today, so I would certainly plan a strategy to turn around early and carry tools to prevent a long sliding fall on icy terrain that hasn’t softened. Solar gain in the snow is the main driver of our avalanche hazard today as deeper weak layers are bridged over by a stiff slab of refrozen snow. The frozen surface is helping to keep the spread out the stress of humans  through the upper layers. Generally, this bridging will continue even if the limited heating pans out today. One other factor in our favor is the the weakest of our weak layers has been swept out of most of the Lip and some of the Sluice by avalanches after the ice crust and faceting occured. That said, I would still practice safe travel techniques and carry avy gear. Right Gully and Lobster Claw are mostly free of this layer and benefit from other stability factors.

OTHER HAZARDS:  Long sliding falls are a hazard today. Icy, refrozen snow will limit penetration of boots or skis. Crampons and an ice axe are recommended for travel on steeper slopes. Micro-spikes and other creeper style traction devices maybe helpful on some low angle approach summer trails, but they do not provide the security of crampons.  Also begin looking for undermined snow bridges and open holes, most likely found moving down the brook bed from the Bowl to the Little Headwall. The Harvard Cabin is closed for the season.

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. Posted 8:15a.m. 4-4-2014. 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

2014-04-04

Avalanche Advisory for Thursday, April 3, 2014

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

Though heating of the snowpack is not likely today, expect avalanche danger to increase if temperatures rise significantly or more direct sunlight hits south facing slopes than is forecast.

AVALANCHE PROBLEMS: Currently the temperature on the summit is 10F and has remained well below freezing all night. This cold air has refrozen our snowpack and strengthened surface layers. Weak layers below will be much more difficult to trigger as a result, but Persistent Slabs will remain our number one avalanche problem today.

WEATHER:  Cold air will only warm from 10F to about 18F on the summit today. NW winds from 45-60 mph will decrease this afternoon.  Overcast skies will return later today with a chance of snow showers.

SNOWPACK:   Snowpack stability is currently at the whim of temperatures and melt freeze cycles.  Yesterday a number of areas were at a Moderate rating due to warm conditions penetrating into the snowpack. A number of locations became wet at the surface, particularly those with a S aspect.  Since the summit high of 31F (-1C) on Wednesday the mercury has fallen sharply to a current of 10F with winds from at the WNW at 45mph (73 kph).  This hard freeze has locked up freewater close to the surface and is working deep to chase any liquid water on S facing protected locales like Right Gully that warmed more than others.  This has created a hard yet porous crust that has strengthened the upper snowpack creating a bridge, or thick eggshell, over the deeper persistent issues we have been discussing.  Today temperatures are anticipated to rise, but only into the upper teens.  The overcast skies for a while this morning, and then more clouds later today, will be sandwiched around some midday clearing.  This clearing should let in some sun, but should do little to warm slopes.  Warming to avalanche terrain returns tomorrow, which may decrease today’s bridging strength, returning “Moderate danger” back into the mix. Generally, look for hard freezes at night with minor warm ups during the day initially this early April to let the snow slowly stabilize.

OTHER HAZARDS:  Long sliding falls are emerging as a hazard today. Icy, refrozen snow after the last two day warm-up will limit penetration of boots or skis. Crampons and an ice axe are recommended for travel on steeper slopes. Micro-spikes and other creeper style traction devices maybe helpful on some low angle approach summer trails, but they do not provide the security of crampons.  Also begin looking for undermined snow bridges and open holes, most likely found moving down the brook bed from the Bowl to the Little Headwall. The Harvard Cabin is closed for the season.

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. Posted 8:05a.m. 4-3-2014. 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

2014-04-03-Print Version

 

Avalanche Advisory for Wednesday April 2, 2014

This advisory expires at 12:00 midnight.

Tuckerman Ravine has MODERATE and LOW avalanche danger.  The Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway have Moderate avalanche.  Natural avalanches are unlikely and human triggered avalanches are possible.  The Lobster Claw, Right Gully, Lower Snowfields and Little Headwall have Low avalanche danger.  Natural and human triggered avalanches are unlikely except in isolated terrain features.

Huntington has MODERATE and LOW avalanche danger.  Central Gully has Moderate avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible.  All other forecast areas have Low avalanche danger.  Natural and human triggered avalanches are unlikely except in isolated terrain features.

AVALANCHE PROBLEM: Persistent Slabs is the main problem today leading us to continue forecasting Moderate avalanche danger for a number of areas.  As was mentioned yesterday areas posted at Low do have good stability but I wouldn’t shut off you mind to nature’s signs leading to avalanche problems.  Excessive heating is the bulls-eye factor leading towards instability so be on the lookout for warming that penetrates into surface slabs weakening them.

WEATHER: Partly sunny skies will prevail this morning before clouding over later today with a chance of snow showers.  Precipitation totals will be scant.  Winds from the W will increase from 30-40mph to 40-55mph later.  Warm temperatures will reign early today, holding above freezing, and then falling through the day and evening before settling in the lower teens.  This morning there are several thermal bands that will likely mix and even out through the day. Avalanche terrain is currently above freezing.

SNOWPACK:  If you’ve been reading our advisories recently you’ll note that persistent slabs have been the issue of late.  This continues to be the main problem to be aware of, but as we move through melt freeze cycles this should abate.  Overnight we went through a brief refreeze, but it did not sustain for long which keeps the persistent concern an issue for me.  When the snowpack stays above freezing around the clock the snowpack loss of strength penetrates more deeply than a consistent 50/50 melt freeze cycle.  The main concerns now are from the Sluice across to the Chute hence their Moderate rating, followed by Left Gully and Hillman’s Highway.

Long overnight refreezing, such as the temperatures we will see tonight, limits the melting and weakening of the snowpack that occurs during the day and locks up surface slabs bridging over weaknesses below. This will likely move us towards some areas at Low tomorrow.  Generally, look for hard freezes at night with minor warm ups during the day initially this early April to let the snow slowly stabilize.

OTHER HAZARDS: Undermined and collapsing snow bridges will likely be the first ‘spring time hazard” to be on the lookout for.  This is mostly an issue for those moving down the brook from the Bowl to the top of the Little Headwall.  Besides avalanche concerns and undermining, the typical objective spring hazards have been held at bay due to the recent late winter conditions.  The Harvard Cabin is closed for the season.

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 or the staff at Hermit Lake Shelters or Pinkham Notch Visitor Center.
  • Posted 8:48 a.m. 04-02-2014. 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

Print friendly version

Avalanche Advisory for Tuesday, April 1, 2014

This advisory expires at 12:00 midnight.

Tuckerman Ravine has Moderate and Low avalanche danger. The Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s 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.

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

AVALANCHE PROBLEMS: Today’s danger ratings are not the type of danger where you just look at the slat boards and keep moving. Read on for more details.

Problem #1 is persistent slab. The greatest threat from this will be in the Moderate rated areas of Tuckerman that have a SE aspect, but you should be assessing for this threat wherever you travel. Remember that a Low rating means avalanches are unlikely, which is not the same as saying impossible. This threat will increase during the day as the existing crust layer loses its strength.

Problem #2 is loose wet avalanches. These are sometimes called sluffs and tend to be smaller and slower moving than slab avalanches. However, they can easily sweep you off your feet, which can have serious consequences depending on the terrain. South-facing slopes will be the prime location for this threat.

WEATHER: Today might be one of the first days where we truly get spring-like weather conditions. Diminishing winds, warm temps, and ample sunshine should make it a pleasant day to be in the mountains. Don’t take my word for it though, you should always check the summits forecast before heading out.

SNOWPACK: The snowpack on the entire mountain is encased is a lovely crust this morning. This was formed by warm temperatures late Saturday followed by a freeze. We do not believe this warmth penetrated deeply enough into the snowpack to negate all the potential weak layers in the sub-surface snowpack. However, the crust currently adds a lot of strength to the snowpack. Today, this crust will be subjected to warmth and sunshine, which should cook through the crustiness, especially on south and east facing slopes. As this crust is warmed, it will lose its strength. The two most notable effects of this are that the skiing and riding surface will improve tremendously and that any underlying weak layers will be more susceptible to impacts from people traveling over them. More appealing conditions coupled with increasing hazard should make you think twice. Take the time to assess the snowpack, be aware of changing conditions, and expect lots of spatial variability.

The persistent slab problem responsible for the recent large avalanche on the summit cone may exist in a variety of locations in Tuckerman and Huntington. In some locations, this layer was affected by avalanche activity already and so poses less of a threat. This includes some portions of the Lip and Center Bowl but not all of it. The Sluice and Chute are locations where you may find this problem, as well as Central Gully in Huntington. Thankfully, Right Gully and Lobster Claw had very little snow at the time when this layer developed, so I do not think it will play a prominent role in avalanche hazard there. Hillman’s and Left Gully may also have this issue, but will be slower to warm today and therefore it’s less likely that you’ll be able to impact the layer, but if you do the outcome would be a large slab release.

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 or the staff at Hermit Lake Shelters or Pinkham Notch Visitor Center.
  • Posted 8:30 a.m. 04-01-2014. 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

2014-04-01 Print Friendly