Avalanche Advisory for Friday, January 31, 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 danger. Natural avalanches are unlikely and human triggered avalanches are possible. Expect heightened avalanche conditions on specific terrain features. All other forecast areas have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

Huntington Ravine has Moderate and Low avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible in Central, Pinnacle, Odell, South and Escape Hatch gullies. Expect heightened avalanche conditions on specific terrain features. North, Damnation, and Yale have Low avalanche hazard. Natural and human triggered avalanches are unlikely.

AVALANCHE PROBLEMSWind Slab and Persistent Slab are still the two avalanche problems you will face today. Wind slab formed from new snow earlier in the week loaded on W winds.  The complexity of the avalanche problem increases where Persistent Slabs and Wind Slabs co-exist. Hollow sounding, stiff wind slab is more dangerous where it has developed over the weak layer of facets. These slabs are far from touchy but remember that they can still propagate a crack and fail if the right trigger is hit.  Evaluate your snow and terrain carefully.

WEATHER:  A slight chance of snow showers today with summit fog at times. Highs in the mid-teens around the mountain and colder on the summit. West winds in the 60-70 mph (95-110 kph) range will keep things real today above treeline and in the ravines. Continued cold temperatures in our avalanche forecast area for the next 36 hours will nourish our facet gardens. The next chance for significant snow fall is Saturday night when 3-5 inches (8-12 cm) is possible.

SNOWPACK: A snowpack needs a weak layer as well as an ability to propagate a crack in order to produce an avalanche. Field work and compression tests yesterday in Hillman’s and Left Gully revealed two weak layers. Nearest the surface, a weak interface between the hard, surface wind slab and the slightly softer wind slab beneath was the first to fail during compression tests. This layer would slide out in places were it was undercut such as at a switchback or obviously in a test pit where it failed in CT 9 or 10 range. More disconcerting was the 1-5 cm weak layer of 2-3 mm facets found in many locations anywhere from 50-70 cm down on top of the January 11 rain crust (and below a thin temperature crust) which failed in the CT 21 range. A party in Hillman’s wisely retreated after a whoompf and shooting crack near the fork confirmed their suspicions of the slope. The safest bet for travel is stay on the rain crust surface only venturing out onto the hollow wind slabs when you have some contingency plan in place, like a belay and known stable surface or safe zone nearby.  This wind slab is hard and strong and, like most persistent weak layers, exceptionally hard to predict the exact trigger point or load required to bring about failure. Extended column test and propagation saw tests confirmed the stubborn nature of the slab and also point to the challenge of moving around safely. Conservative travel strategies are your best bet for handling this hazard.

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 830am 1-31-2014 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

2014-1-31 Print friendly

Avalanche Advisory for Thursday, January 30, 2014

This advisory expires at 12:00 midnight.

Tuckerman Ravine has Moderate and Low avalanche danger. The Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway have Moderate danger. Natural avalanches are unlikely and human triggered avalanches are possible. Expect heightened avalanche conditions on specific terrain features. All other forecast areas have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

Huntington Ravine has Moderate and Low avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible in Central, Pinnacle, Odell, South and Escape Hatch gullies. Expect heightened avalanche conditions on specific terrain features. North, Damnation and Yale have Low avalanche hazard. Natural and human triggered avalanches are unlikely.

AVALANCHE PROBLEMSWind Slab and Persistent Slab are still the two avalanche problems you will face today. Wind slab formed from new snow several days ago loaded on W winds.  The 9” of +/- 5% snow created soft slab that has been slow to change due to very cold air. A number of locations also have existing stability issues due to facet induced persistent slabs that has been developing over the last couple of weeks. The complexity of the avalanche problem increases where Persistent Slabs, are over or intermingled with Wind Slab.  Evaluate your snow and terrain carefully.

WEATHER:  You know you must be getting acclimated to this winter’s weather when today’s forecast looks nice for climbing. Temperatures will push up into the high single digits fahrenheit (-15 to -12C) on the summit from the current reading of -8F (-22C). High winds in the 90 mph (145 kph) range blew in the wee hours of this morning, contributing to the scouring action that resulted in lower hazard ratings in Huntington’s northern gullies. Wind speeds are forecast to slow and already appear to be moderating with a peak 15 minute windspeed on the summit of just 41 mph at 7:15 am.  According to the MWOBS forecast, winds will shift today to the southwest and blow 30-45 mph. Winds will ramp up again into the 75 mph range punishing anyone out late tonight. Temperatures forecast for the foreseeable future may encourage facet growth and slow stabilizing trends.

SNOWPACK: Same scratchy vinyl record you ask?  Yup here we go again, persistent slabs and facets are the driver of our concerns right now. The current cold clear weather, academically speaking, should be increasing the rate of facet growth.  We will be on the look out over the next couple of days for what changes are actually occurring, we encourage you to do the same.  “Wind slabs” will likely transition to being called “persistent” over the next 24 hours.  This is due to the days on the ground and the changes they are likely undergoing with clear cold conditions.

Open your mind to the current facet problem.  Realize randomly distributed weaknesses are buried and difficult to ascertain consistently through surface visuals, as well as through digging.  Expect ‘false stable’ field tests in some locations and be quite cautious making universal travel decisions based on a stable snow pit.   False stable tests mean that you get good stability results in your pit, but it does not accurately reflect the reality of the weaknesses randomly distributed across the snowpack.  So what do you do?  Well it is challenging when some hidden timebombs exist that are difficult to find, no doubt about it.  Be cautious, move slow to properly determine stability, consider run out risk if something does occur, assure safe travel practices for your party, avoid big lines, be happy with a little fun and save big days for more straight forward conditions.  You get the drill, go easy out there to come back another day!

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 830am 1-30-2014 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

2014-01-30 Print friendly

Avalanche Advisory for Wednesday January 29, 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 danger. Natural avalanches are unlikely and human triggered avalanches are possible. Expect heightened avalanche conditions on specific terrain features. All other forecast areas have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

Huntington Ravine has Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Expect heightened avalanche conditions on specific terrain features.

AVALANCHE PROBLEMS: Wind Slab and Persistent Slab are the two avalanche problems you will face today. Wind slab has formed in response to 9” (23cm) of snow between Saturday and Monday with a generally W wind direction. A number of locations have existing stability issues due to facet induced persistent slabs that has been developing over the last couple of weeks. Persistent slabs under new wind slab have a more complicated and spatially variable distribution of avalanche hazard. Evaluate your snow and terrain carefully.

WEATHER:  Yesterday dawned very cold with drifting and blowing snow with high winds.  As Tuesday afternoon came about, winds subsided to moderate speeds and a high pressure clearing trend began.  Temperatures began this morning at -10F for the higher summits and will slowly warm over the next 36 hours to about +10F late on Thursday.  Winds will build today gusting over 70mph towards darkness.  A slight weather disturbance will produce a brief period of clouds late today with a chance of some light snow before clearing again overnight and Thursday.

SNOWPACK: As Jeff discussed yesterday, crown lines from avalanches on Sunday and Monday are visible in Tuckerman Ravine highlighting signs of instability.  Yes, the level of instability has declined from the peak new snow loading periods that produced these natural avalanches.  However, we continue to be concerned about both weaknesses within the new windslab, and the more ominous and elusive weak facets, producing our persistent slab problems.   Our colleagues at western avalanche centers are challenged to keep backcountry users attention after days or weeks of persistent slab problems.  The persistent problem we have right now is atypical of an eastern snowpack so expect to find different conditions than what you are used to seeing. Therefore, we ask you to keep this facet problem on the forefront of your mind if venturing into avalanche terrain.  Anticipate finding the spectrum within the Moderate rating.  Some locations like the northern gullies (North, Damnation, and Yale) in Huntington, and the Sluice in Tuckerman, are close to Low. While some places with a more E facing aspect are in the middle to upper end of Moderate, due to a combination of wind slabs and persistent slabs.

As time progresses this persistent issue is becoming more widely dynamic.  If you were able to map these facets accurately you would see them become more ‘spatially variable’.  Some areas of facets have been wiped out by avalanches and some scoured out by wind. Others locales have intact 2-3mm weak faceted crystals under thin pencil hard slabs while other places they are barely approaching 1mm in size.  These preserved locations with 1-3mm facets are our main concern. Yet they are nearly impossible to identify and avoid from a distance as sweet spots for triggering because of their random and widespread existence.  Field time yesterday had stability tests that were dramatically different producing results as unstable as ECTPV (fracture propagates upon isolation with no load/taps).  It will very important to remember that tests are telling you what’s going on under your feet, but may not only meters away.  I would also be very concerned being under other users that are traveling above you.  Over the next 2-3 days we are expecting fairly cold and clear nights contributing to continued facet development.

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 830am 1-29-2014 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

2014-01-29 Print

Avalanche Advisory for Tuesday, January 28, 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 danger. Natural avalanches are unlikely and human triggered avalanches are possible. Expect heightened avalanche conditions on specific terrain features. All other forecast areas have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

All forecast areas of Huntington Ravine have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Expect heightened avalanche conditions on specific terrain features.

AVALANCHE PROBLEMS: Today you will be facing a combination of wind slab and persistent slab problems. In this case, new wind slab has formed in a variety of locations, some of which had existing stability issues due to persistent slab. In short, the locations where there are persistent slabs underlying new wind slab have a more complicated and spatially variable distribution of avalanche hazard. Evaluate your snow and terrain carefully.

WEATHER: Today’s avalanche issues are being driven by past weather more so than expected weather today. Over the past three days, the summit is reporting about 9″ (18cm) of new snow. In the last two days, we’ve seen very strong winds, gusting up to 121mph and 114mph each day (195 & 183kph). Except for a brief rise, temperatures have been well below normal. Today we should see winds diminish somewhat, heading down toward 40-55mph (64-88kph) from the W. I expect wind loading to subside today due to limited snow available after such strong winds, along with the decreasing velocities.

SNOWPACK: If you come up to the Bowl today, you’ll see a prominent red flag staring you in the face, as well as a couple smaller ones. I’m referring to a crisp avalanche crown line in the lower portion of the Center Bowl. You can’t miss it. Look around a little more and you’ll also see crowns in other areas near the Headwall, such as the Lip and near the Chute. These are excellent indicators of unstable snow! The Center Bowl avalanche is recent, some of the others are as old as lunchtime on Sunday.

The snowpack right now is an intensely variable mix, due to previously existing faceted layers under hard slabs, new wind slab from the last 24-48 hours, and the recent avalanche activity with various degrees of reloading. If it weren’t for the persistent slab/facet layer, the recent winds may have been strong enough to bring some areas down to Low danger. Most of Huntington is one example, Hillman’s Highway is another. These areas often see a lot of scouring when winds are as strong as they were. However, the persistent nature of the existing instabilities gives me insufficient confidence that these locations are stable enough to call Low. Keep in mind that the snow underfoot may feel hard and strong, but there may be weak layers lurking underneath waiting for you to reach a thin spot or other weakness. Constantly be assessing the snow as you move through the terrain today!

Please Remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
  • Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
  • For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.
  • Posted 8:40 a.m. January 28, 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

2014-01-28 Print Friendly

 

 

Avalanche Advisory for Monday, January 27, 2014

This advisory expires 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 avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. All other forecast areas have Moderate avalanche danger. Natural avalanches unlikely and human triggered avalanches are possible.

All forecast areas of Huntington Ravine 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.

AVALANCHE PROBLEMS: Avalanche hazard will be increasing through the day. 3-6″ (7.5-15cm) of new snow on loading winds will build into wind slabs today. Persistent slabs due to a weak layer above the old rain crust also exists though it is impossible to determine exactly where these sugary facets will be a problem. Brief clearing yesterday afternoon revealed avalanche crown lines high in the Lip, low in the Lip above the Open Book, low and right of Chute and into Center Bowl. Other areas went unobserved. Areas will reload today on moderate then strong winds creating harder wind slab over a softer, potential failure layer.

WEATHER: Winds are currently out of the southwest at 55-65mph (85-105kph) and will shift west and increase in velocity to the 70-90mph (113-145kph) range, according to weather models and NWS forecasts. Snow showers and squalls are forecast, but currently, steady light snow is falling at Pinkham Notch and Hermit Lake. Southwest winds today will challenge Lion Head hikers who will be exposed from treeline to the summit. Temperatures will plummet again with the latest arctic cold front to sail through the area. Winds will most likely do some scouring of south facing Huntington gullies later this evening as speeds ramp up.

SNOWPACK: Two major avalanche concerns exist in our snow pack right now.  The new wind slab will build in size proportional to new snowfall today. Our nemesis, spatial variability, will show her ugly mug as these wind slabs shift locations as the winds shift, depositing snow in differing lee areas. As winds speed up it will break up and pack particles into denser slabs while building slabs further down in gullies and lower start zones. To complicate things further, the faceted weak layer, where it still exists, will be further stressed by the weight of new slabs. So, if you are a superhero impervious to traumatic injury, go dig a bunch of snowpits and let us know what you find. Until we get some clearing and calmer weather, our field work will be limited.

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. January 27, 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

2014-01-27 Print friendly

Avalanche Advisory for Sunday, January 26, 2014

This advisory expires at 12:00 midnight.

Tuckerman Ravine has CONSIDERABLE and LOW avalanche danger. The Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. All other forecast areas have Low avalanche danger. Natural and human triggered avalanches are unlikely except in isolated terrain features.

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

AVALANCHE PROBLEMS: The primary avalanche concern today is new wind slab building through the day. Increasing wind speeds are causing a strong-over-weak scenario to unfold, which is a common theme for unstable snow. Additionally, any new slab development will be taking place on top of a snowpack with intense spatial variability, and in many areas there were already existing stability concerns before this new wind slab problem arose. The previously existing problem has been described in earlier advisories as a persistent slab problem. This still exists and makes today an even more complicated day for travel in avalanche terrain. Faceting has weakened snow layers lying beneath some harder slabs. These are reactive to triggers such as a person traveling over them, especially in locations where the hard slab is thin.

WEATHER: Currently the summit of Mt. Washington is at -26F (-32C) with winds gusting just shy of 100mph (161kph). These are very challenging conditions for travel above treeline. Even down lower on the mountain, we caution you to be conservative with your decisions today. Yesterday, the summit of Mt. Washington reported 4.4” of new light density snow. At Hermit Lake we measured 5” (12.5cm), although the snowplot had some drifting on the boards. This snow is creating the new wind slab issues, and will be limiting visibility both above and below treeline. Expect slight relief from the cold and wind later in the day, but not so much that I’d call it a comfortable day. More new snow is in the forecast for Monday. At this point, we’ll take all we can get!

SNOWPACK: Once again, spatial variability is the name of the game. Conditions varied widely as you moved around the terrain earlier this week, and the current weather will only add another layer to the mix of conditions. It will be very difficult to effectively assess an entire route from only a handful of observations. Generalizations and extrapolations can only go so far. You’ll need to constantly be alert to changes in the snowpack.

The January 11 rain crust is a good baseline to start from. Above this you’ll find faceted snow of varying thicknesses and varying levels of facet development. In many locations, you find a layer of pencil hard slab on top of the facets, again, thicknesses and strength will vary. Some other locations do not have this hard layer and others may have been scoured down to the crust. On top of all this is the new wind slab problem described above. Some areas will have a hard time holding onto the new snow with the winds raging as they are. The northern gullies of Huntington are one example. The expected scouring this morning in these areas will move them from Considerable to the current rating of Moderate for the better part of the day.

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 8:15 a.m. January 26, 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

2014-01-26 Print Friendly 

Avalanche Advisory for Saturday, January 25, 2014

This advisory expires at midnight. 

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

Huntington Ravine has Considerable and Moderate avalanche danger. Central, Pinnacle, Odell, South, and Escape Hatch have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. North, Damnation and Yale gullies have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Careful snowpack evaluation, cautious route finding and conservative decision making is essential.

AVALANCHE PROBLEMS: Generally, we are starting out today with yesterday’s ratings. However, avalanche hazard will increase to our current ratings through the day. Persistent slabs will compete with wind slabs as our primary avalanche hazard today. A weak layer of facets lurks beneath older wind slabs in many areas which can crack and propagate into a medium size avalanche.  New snow on strong SW then S winds will build new wind slabs in north facing aspects and cross load other areas. This new loading will increase the chance of avalanches later today. Also, visibility will diminish through the day and hamper assessment of snow and terrain and complicate safe travel strategies.

WEATHER: A cold front is bringing snow to the mountains today. Winds from the southwest at 60-80 mph (97-130kph) will shift south and drop to the 50-70 mph (80-113kph) range with higher gusts. Not only will this wind velocity be sufficient to load snow into northerly aspects and crossload areas facing more to the east, it will hammer people on the Lion Head trail much harder than the usual northwesterlies do since there will be no windbreak from the summit cone. Projected wind speeds from this direction will make walking difficult above treeline all the way to the summit and be in your face descending the cone. The 2-4″ (5-10 cm) of new snow will fall through the day, increasing in intensity through the day.

SNOWPACK: The weak layer of sugary facets that has developed during the past week will continue as low air temperatures drive the faceting process. Deeper wind slabs from last Sunday and Monday’s strong westerly winds may be more reactive as the process reaches through the insulating layers of deeper snow to the less permeable melt-freeze crusts that support the growth of these cup shaped crystals. Steep slopes with these pockets may not require you to find a thin spot in these slabs to serve as a trigger and may react only to your weight. Be fast climbing today, but protect yourself on or beside otherwise easy steep snow climbing. Avoid these steep pockets and remember that the slabs are hard enough that they will support your weight but may be undermined by the persistent weak layer of facets. As additional snow adds to the load later today, it will become easier to your weight to tip the balance.

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. 1-25-2014. 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 

2014-1-25 Print friendly

Avalanche Advisory for Friday, January 24, 2014

This advisory expires at midnight. 

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

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

AVALANCHE PROBLEMS: Human triggered Persistent Slabs are the primary avalanche concern today. Continued cold conditions have allowed facets to grow above our hard old surface from January 11th, creating a weak layer beneath recently deposited wind slabs. Shooting cracks and/or hollow sounding slabs should raise the hackles for unstable slabs. Snow Rangers triggered an avalanche yesterday and as you know, recent avalanches can be a bullseye sign of further instability. Cold clear conditions have continued the growth of facets overnight causing this weakness to increase our Persistent Slab problem.

WEATHER: Currently summit temperatures are climbing from a low last night of -21F to an expected high of -10F later today.  Winds from the NW, at a steady 30 mph, should shift to the W and gust to over 55 mph at some point this afternoon.  Tonight and tomorrow we expect 2-4″ of new snow with higher localized amounts with some squalls.  This, associated with a strong building winds will cause additional avalanche problems.  On Sunday, temperatures could be the coldest yet this season.  Models have yet to come into alignment, but expect -20/-25F with hurricane force winds as a working assumption.

SNOWPACK: There is a complex and variable facet problem in the Ravines right now.  As we pointed out yesterday, you should  “examine older deeper slabs for facet development that we are calling persistent“.  We’ll try to line it out as clearly as possible.

Since the last rain event 2 weeks ago we have picked up about 15” (38cm)of snow that trickled in a little at a time.  This was loaded in on a variety of aspects, then scoured and redistributed in others, with occasional high winds.  As of several days ago this left us with a high amount of wind slab spatial variability.  Cold air and three days of clear skies rapidly caused faceting to develop.  This is the changing of crystals from rounds, into icy, square, weak sugar snow.  Because the wide distribution of the previous wind slabs varied so much in depth we have seen grossly different temperature gradients.  This has caused a mind numbing patchwork of facet development.  We are currently the poster child for spatial variability!  You will find facets in some places that are 2mm in size, stacked 7-10cm thick.  This may be found near the surface within the old windslab under 15cm of pencil hard slab or 30cm down on top of the last rain crust.  In some places it’s 1-2mm in size under a south facing sun crust and in other facets get quite large acting as “sweet spots-triggering locations” near our many rocks and cliffs.  You get the point-“Russian Roulette Moderate”!  Do not rely on stability tests to say much about what is going on except right where you’re standing.  Be wary of “false stable” test results.

To boil it down: The wind slab is on top of weak facets in an advanced state of growth in wind loaded areas. Be wary traveling out onto hard slabs that you felt comfortable on during previous trips. Expect facets under these pencil hard slabs.  This weak layer is mostly found on the old, hard surface beneath these slabs in many areas in both ravines in our forecast area.  ECT&CT1 through 11 test results were common.   Stronger wind slab layers, stacked on weaker faceted ones, are creating the persistent slab issue. This snow structure varies widely in thickness and distribution and could propagate long distance if you find the right trigger point!  Check out the embedded links in the advisory to see videos of yesterday’s avalanche.  Also be sure to check out our Pit post and Weekend Update later this afternoon.

Please Remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
  • Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
  • For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.Posted 830 a.m. 1-24-2014. A new advisory will be issued tomorrow.

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

2014-01-24 Print

Avalanche Advisory for Thursday, January 23, 2014

This advisory expires at midnight. 

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

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

AVALANCHE PROBLEMS: Human triggered Wind Slabs and Persistent Slabs are the main concern today.  Cold weather is still dramatically slowing slab problems from stabilizing. Continue to expect an intense amount of spatial variability. Some areas of slab have been sitting for about a week and are clearly persistent.  With clear cold conditions in place we will be looking for facet development in these older slabs today.  Wind slabs from more recent snow on Monday haven’t changed too much due to cold air slowing consolidation and sintering.  These will likely lump into the Persistent Slab category by tomorrow depending on what we find today.

WEATHER: Temperatures continue to be very cold and are the discussion point of choice.  At higher elevations, mercury will dance around -10F (-23C) and then drop to about -20F (-29C) tonight.  Winds will shift from NW to W this morning, and build to 45-50mph (72-80kph) late this afternoon.  These velocities are far from what the mountain can deliver, but coupled with sub-zero air, they should be respected.  Skies will move from clear to overcast later.  Weather models looking out towards the weekend are making me nervous.  Although temperatures may rebound a bit on Saturday, flirting as high as a balmy zero, that will change.  Our gauges may fall lower than they have yet this year on Saturday night and Sunday morning  with winds in excess of hurricane force.  Start watching the weather closely if you are planning a weekend trip.

SNOWPACK: There is a lot of spatial variability in areas both rated at Low and Moderate.  You will find icy old surfaces from the last rain event with nearby dry slabs, knee deep or more, all within 30 meters or less of one another.  This situation is common for us due to our high winds and their scouring effect.  Be on the lookout for weaknesses from new snow buried at different depths, depending on location, from precipitation that fell on Sunday and Monday.  Snow initially loaded on light W winds before speeds increased to create denser slabs.  These stronger layers, stacked on lighter weaker ones, is the main wind slab avalanche problem in areas posted “Moderate”.  Also examine older deeper slabs for facet development that we are calling persistent.

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 800a.m. 1-23-2014. 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

2014-01-23 Print

Avalanche Advisory for Wednesday, January 22, 2014

This advisory expires at midnight.

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

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

AVALANCHE PROBLEMS: Human triggered Wind Slabs are the main concern today.  Areas posted at Moderate have larger areas of new wind slab; areas posted at Low danger may also have unstable wind slab, though they are smaller and more isolated throughout the gully or snowfield.  Expect an intense amount of spatial variability.  Cold weather is dramatically slowing this wind slab problem from stabilizing. Tomorrow we may start considering slabs in place as Persistent Slabs.

WEATHER: Temperatures continue to be very cold today with a high of about -10F (-23C), dropping to -15F (-26C) tonight.  Winds speeds from the N are expected to increase through the day, perhaps gusting over 50mph this afternoon.  The high pressure is presenting us with a dry, 22% relative humidity, air mass and no real precipitation in the extended forecast.  As was discussed yesterday the avalanche problem you’ll be facing today is a result of recent weather history.  Over the past several days 4+” (10+cm) of new snow was loaded into the Ravines from predominantly westerly winds, with gusts as high as 95mph (153kph).

SNOWPACK: There is a lot of spatial variability in areas both rated at Low and Moderate.  Over the past 28 days we have had 24 days with recorded snow, but the dramatic swings giving us rain and warm temps have crushed this joyful news. However, over the last 10 days since rain, cold air, upslope snow, and a storm event has produced 15.5” (38cm) of snow.  This snow has been loaded in from all points of the compass rose, predominantly from the W and NW.  You will find icy old surfaces from the Jan 11th rain event with dry slabs on top, knee deep or more, within half a rope length.  This classic Mount Washington scenario can be found in numerous locations.  A good example of this is in Tuckerman’s Left Gully where hard old surfaces play leapfrog with newer slabs as you move up and down as well as side to side.  With some clearing sky conditions and cold air we will be on the lookout for facet development.  This will develop weak layers within the existing slabs causing a persistent slab concern.

There are days “Low” can mean rock solid everywhere, while at other times we have concerns about isolated pockets of unstable slab.  These instabilities within isolated terrain features can certainly be problematic.  Their actual stability can be similar to the slabs in areas posted at Moderate, but they are not consistently found throughout a forecast area, or are easily negotiated around and can be avoided with little difficulty.   Low is often used when these isolated areas are obvious to determine such as the difference between old rock hard ice, peppered with isolated slabs.  An example of this is high up in the Huntington’s northern gullies which have scant snow coverage.  But there are snow instabilities here that you should be on the lookout for. Good route-finding in these gullies will go a long way to keeping you out of harm’s way.

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 755a.m.1-22-2014. 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

2014-01-22 Print