Avalanche Advisory for Friday, January 16, 2015

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. All other forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely, although unstable snow in isolated terrain features may exist.

Huntington Ravine has Moderate and Low avalanche danger. North Gully, Damnation, Yale, Central, and Pinnacle have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Odell Gully, South, and Escape Hatch have Low avalanche danger. Natural and human-triggered avalanches are unlikely, although unstable snow in isolated terrain features may exist.

AVALANCHE PROBLEM: Persistent Slabs are the #1 avalanche problem today.  Wind slabs laid into the Ravines at varying times over the past 10 days have all transitioned to being “Persistent”.  These slabs are sitting on weak faceted crystals that are advanced in some areas depending on the specific layering unique to that location.  We are not finding these weaknesses consistently across the terrain, but in varying degrees so expect a lot of spatial variability in how these facets effect the Persistent Slab issue. The best ways to manage the risk from Persistent Slabs is to make conservative terrain choices. The slabs can propagate in surprising ways making this problem more difficult to predict, assess and manage than wind or storm slabs requiring a wide safety buffer to handle the uncertainty.

WEATHER: A chance of snow showers today should remain light and not contribute to snow instability, but will hover over the mountain effecting visibility for a while.  Temperatures will drop rapidly from positive territory deep into negative terrain through the day, perhaps hitting -30F tonight.  This will be associated with a mean, ripping wind, gusting to 115mph (185kph) around midnight.  By dusk today expect winds to be approaching the century mark.  Saturday morning will start out rugged with full arctic conditions, but temper through the day due to dropping winds and rising mercury.

SNOWPACK: Moving around in the Fan of Huntington Ravine to the ice bulge in Central Gully yesterday was a good way to drive home the point that our snowpack is highly diverse from one point to another. Boot and ski penetration varied from place to place, but the opportunity to travel in boot height snow was plentiful. The ice crust vapor barrier that is contributing to the development of our faceted weak layer was found at varying depths and thicknesses. At times it was near the surface and highly fragile.  We dug numerous hand pits in areas of softer snow in the Fan, beneath the Central bulge and along the way over towards Harvard Bulge.  This route confirmed the presence of the weak layer of advanced 1-2mm facets. The good news is the slab on top is stubborn and not very reactive in most locations. The concern and uncertainty lie in those locations where the slab is under greater tension, i.e. really steep, convex or in locations where there are thin spots that would be more reactive to a human trigger. Stability tests that demonstrate “good stability” can trick people into thinking persistent slabs are fine, until someone hits one of these “sweet spots” due to the current spatial variability. Safe travel techniques are warranted, whether the rating is Low or Moderate, particularly when dealing with Persistent Slabs. Looking ahead, sustained cold could set us up for problems when this snowpack gets stressed with more snow or rapid warming.

The Sherburne ski trail is a nice alternative for people looking to ski without exposing themselves to this today’s high winds and cold. The summer Lionhead trail remains open.  Look for our Weekend  Update 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 7:45 a.m. January 16, 2015. A new advisory will be issued tomorrow.

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

2015-01-16 print friendly

Avalanche Advisory for Thursday, January 15, 2015

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. All other forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely, although unstable snow in isolated terrain features may exist.

Huntington Ravine has Moderate and Low avalanche danger. North Gully, Damnation, Yale, Central, and Pinnacle have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Odell Gully, South, and Escape Hatch have Low avalanche danger. Natural and human-triggered avalanches are unlikely, although unstable snow in isolated terrain features may exist.

AVALANCHE PROBLEM: Continued cold temperatures have worked against stabilization of Wind Slabs in our terrain. These pencil and finger hard slabs are a close second to our primary avalanche problem of Persistent Slabs. You’ll find both of these slab problem types scattered around strong lee areas such as Lip, Center Bowl and Chute in Tuckerman and in parts of Yale and Central in Huntington.  Plenty of old, hard surface exists to travel on in most areas so you can pick a route which reduces your exposure to these slabs.

WEATHER: Looks like a nice day on tap in the high country, with mostly clear skies. Southwest winds in the 15-25 mph, (24-40kph) range with temperatures in the mid-teens F before dropping to around 0F (-18C) tonight. Mostly clear conditions tonight with relatively warm temperatures today will again create conditions counter to the stabilization of our existing slabs.

SNOWPACK: With at least a little precipitation falling on 15 out of the last 18 days and temperatures deep into negative territory, snow has been slow to stabilize. We’d like to say that this nickle and diming snow accumulation is actually giving us substantial gains, but alas we can’t. However the new windslabs of late have been transitioning into persistent slabs that are holding on to their weak layers around both Ravines.  That said, these instability issues are not widespread due to the modest new daily loading only delivering scattered pockets.  You will find faceted crystals varying in size from 1-1.5mm depending on how deeply the January 4th wet snow is buried.  This fact translates directly to the strength of the pressure gradient driving the faceting process.  Under thin slabs you should find larger facets that are weaker than those buried deeper and therefore insulated better from the recent very cold air. Experienced users with avalanche skills should be able to pick out these heightened areas of concern and stick to older surfaces. Careful route selection will certainly play a strong part in staying away from the most recently developed wind slabs and the aforementioned slabs that have just transitioned to “persistent”.  As discussed yesterday, the wide open snowfields in Tuckerman allow more options for a traveler to avoid areas where the stability isn’t good. In Huntington, choke points in the gullies or wall-to-wall slab leave climbers with the choice of going up, going down, or escaping out into rock climbing. The northern gullies of Huntington have the greatest likelihood of harboring unstable snow, while the southern gullies (i.e. Odell, South, Escape) received much less of the recent snow and will have more stability.

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 7:55 a.m. January 15, 2015. A new advisory will be issued tomorrow.

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

2015-01-15 print friendly

 

 

Avalanche Advisory for Wednesday, January 14, 2015

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. All other forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely, although unstable snow in isolated terrain features may exist.

Huntington Ravine has Moderate and Low avalanche danger. North Gully, Damnation, Yale, Central, and Pinnacle have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Odell Gully, South, and Escape Hatch have Low avalanche danger. Natural and human-triggered avalanches are unlikely, although unstable snow in isolated terrain features may exist.

AVALANCHE PROBLEM: Recently formed wind slabs are the problem to watch for again today. Overall, you may find a lot of locations with good stability from firm, wind-affected snow or areas with older crusty surfaces. The wind slab problem will be most pronounced in strongly protected lee areas such as the Lip in Tuckerman or the midsection of Yale Gully in Huntington. Other areas may have firm wind slab with crust or decomposing crust beneath that could act as the weak layer. The Center Bowl is one example of where this might be found today.

WEATHER: Compared with the -10F temperatures at my house this morning, the +12F here at Hermit Lake feels downright comfortable. Light winds and sunshine will likely prevail today while temperatures rise, which will make for a pleasant day to be out on the mountain. Monday the summit recorded a little more than 4” of new snow, but lower elevations received lower amounts.

SNOWPACK: Looking at the big picture, there are plenty of options for travel where stability will be good. Old surfaces and strong, firm snow are the dominant surface characteristics, especially in Tuckerman. Usually Tuckerman has more stability concerns than Huntington, but this is reversed today. In Tuckerman, the wide open snowfields allow more options for a traveler to avoid areas where the stability isn’t good. In Huntington, choke points in the gullies or wall-to-wall slab leave climbers with the choice of going up, going down, or escaping out into rock climbing. The northern gullies of Huntington have the greatest likelihood of harboring unstable snow, while the southern gullies (i.e. Odell, South, Escape) received much less of the recent snow and will have the best stability. In Tucks, Hillman’s and Left Gully are similar to the southern gullies of Huntington with mostly scoured or wind-effected surfaces. Right Gully and Lobster Claw pose lesser threat due to the fact that they are still a long way from being totally filled in. The Lip and Sluice, particularly where the hiking trail crosses, are the slopes that are more likely to have unstable snow.

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 8:10 a.m. January 14 2015. 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

2015-01-14

Avalanche Advisory for Tuesday, January 13, 2015

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. All other forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely, although unstable snow in isolated terrain features may exist.

Huntington Ravine has Moderate and Low avalanche danger. North Gully, Damnation, Yale, Central, and Pinnacle have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Odell Gully, South, and Escape Hatch have Low avalanche danger. Natural and human-triggered avalanches are unlikely, although unstable snow in isolated terrain features may exist.

AVALANCHE PROBLEM: Recently formed wind slabs are the problem to watch for today. These developed in the previous 24 hours and are still receiving some additional deposition from the cascades of low drifting snow blowing in from the alpine zones. I don’t expect the blowing snow to contribute much in addition to existing instability, so what’s on the ground now is what you’ll be dealing with through the day and likely beyond. The locations where you are most likely to encounter snow instabilities are in the Lip in Tuckerman and Yale Gully in Huntington.

WEATHER: Today is starting cold and sunny. Temperatures may not rebound much from their position in the single digits Fahrenheit, but winds are expected to decrease to a modest 20-35mph (32-56kph) and shift from N to NW. Yesterday there was light snow throughout the day, leaving 4” (10cm) or so on the summit. Lower elevations did not record quite as much new snow. There are no significant precipitation events in the coming days.

SNOWPACK: Generally good visibility this morning is allowing for visual assessments of the snow surfaces after yesterday’s weather event. Some of this snow is currently airborne, with clouds of cold smoke drifting across the mountain and down into ravines. The 4” of snow that fell yesterday with NW winds in the 60mph range doesn’t appear to have made much of a difference in snow coverage. The visual clues do indicate there has been some snow loading, but there also appears to be locations where winds have not allowed new slab to develop. The most concerning locations have a smooth surface indicative of new wind slab. While these are not widespread, they may be tender and reactive to triggering. Be watchful for pockets of this even in areas rated Low, such as Odell or Right Gully. A highly textured surface in many areas has me wondering if I’m seeing newly developed and wind-affected slabs, or am I seeing older surfaces with a veneer of bright new snow. You don’t need to read between the lines here. I’ll tell you that I have a lower-than-usual level of confidence in the visual assessments this morning, despite the good visibility. While I suspect good stability in a lot of these textured surfaces, I encourage you to treat them as if they are less stable until you can prove otherwise.

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 8:45 a.m. January 13, 2015. 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

2015-01-13

 

Avalanche Advisory for Monday, January 12, 2015

All forecast areas of Tuckerman and Huntington Ravines 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 PROBLEM: 2-4″ (5-10cm) of new snow today on west winds will create new Wind Slabs in our terrain. The total amount of snowfall will determine the likelihood for these slabs to avalanche naturally and how problematic  they will be for people traveling in avalanche terrain. Areas in the strongest lee of W winds will see the greatest slab development and most potential danger. We are starting out with a Low rating but with isolated terrain features in many areas harboring unstable Persistent Slabs. These old wind slabs were easy to see and avoid yesterday in good visibility but limited visibility and a fresh blanket of snow today will make visual assessment and route-finding more challenging.

WEATHER: Today will be very wintry today with light snow falling throughout the day. The Observatory is forecasting 2-4” (5-10cm) for the higher summits, meanwhile valley locations are expected to get anywhere from 1-3” (7.5-12.5cm). In the mountains this will be accompanied by westerly winds around 50-70 mph (80-112 kph) with stronger gusts. The wind and snow will hamper visibility significantly above treeline, as well as transport snow to the lee areas of the mountain such as Tuckerman and Huntington ravines.

SNOWPACK: The relatively shallow nature of our snowpack is evident to anyone traveling into the ravines. In between the many rocks and water ice flows you’ll find hard gray snow exposed by the scouring action of the wind. Yesterday, touchy one finger wind slabs 10-30cm thick existed in a dimension worthy of respect in many areas. Firmer, pencil hard slabs beneath rested on a decomposing crust over the harder, old snow that was “reset” by rain around the Christmas holiday. I found the thin melt/freeze crust from January 4 remaining in a lee area beneath Chute with a facet layer of varying thickness. It is a weak layer worth keeping on your radar but doesn’t seem to be widespread since much of that crust has either decomposed entirely or been ripped up by the 90+mph winds this past week. Still, it is the deepest weak layer that a human trigger could reach and worthy of considering when in wind sheltered areas. Some slopes like Right Gully, Escape Hatch, and Lower Snowfields have very little snow and would make a difficult bushwhack.

The summer Lion Head Trail remains open and will remain so until we receive more snow. The Sherburne ski trail has improved with all waterbars now frozen and more filled in though not smoothed over. It is still a bumpy ski or ride though the accumulated snow over the past week is keeping it fairly soft.

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. January 12, 2015. 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

2015-01-12 print friendly

Avalanche Advisory for Wednesday, December 31, 2014

This advisory expires tonight at 12:00 midnight. Happy New Year’s Eve, everyone!

All forecast areas of Tuckerman and Huntington Ravines have Low avalanche danger. Natural avalanches are very unlikely and human triggered avalanches are unlikely except in isolated terrain features. Unstable snow may exist in isolated terrain features – use caution in these locations.

AVALANCHE PROBLEM: Similar to yesterday, current avalanche problems are limited to small pockets of wind slab that developed early this week. There is a slight chance for enough snow to fall today that new wind slabs may develop in isolated areas, especially the well-protected leeward slopes in Tuckerman. In both ravines, the overall snowpack is looking rather sparse for the end of December. This means the locations where you may find unstable slab are relatively small and isolated from other areas of snow. This does not mean they are “safe” or that you should leave the beacon, shovel, and probe down in the car. In fact, given the consequences of a fall in the current conditions, any small pocket of unstable snow will be quite dangerous. On the whole, there is a lot of stable snow out there, but don’t let your guard down.

WEATHER: The cold weather has certainly settled in over the mountains. The summit of Mt. Washington has been below zero degrees F for about 40 hours now and may only go a few degrees above at some point tomorrow. A cold front will pass by this morning, providing a chance for some light snowfall accumulations of a trace – 2″ (tr-5cm). Winds will continue to be fairly strong, but may diminish somewhat after the front has passed by. Expect gusts up to 75mph (120kph) this morning. Once again, be prepared for arctic conditions above treeline. You may also face very limited visibility with clouds and blowing snow.

SNOWPACK: Throughout much of both ravines you will find snow with good to very good stability. Exposed crust and wind-packed hard slab are commonplace right now. Both of these surfaces can be very strong and make for good climbing conditions, and they can also make for very rapid descents if you were unable to quickly self-arrest a fall. There are two stability situations you should be watching out for. One is a slab resting on top of a layer of weak snow on top of crust. I saw this in one location beneath Pinnacle Buttress two days ago, and can envision other similar pockets existing elsewhere. The other is any new soft slabs created this morning from new snow and wind loading. I expect both of these to be limited in size and distribution. The true extent of the new slab problem will be determined by the amount of new snow received. If we reach or exceed the 2″ mark, this problem may push the boundaries of Low danger in favorable locations.

In other news, the Lion Head Summer Trail remains open and will be the preferred route until we get significantly more snow. The trail does cross an avalanche path in a couple locations, but there needs to be a lot more snow before this becomes a problem. The John Sherburne Ski Trail has fair coverage but is very hard-packed, icy, and very bumpy. And finally, we will be resuming the Eastern Snow and Avalanche Workshop (ESAW) Continuing Education Series this winter. The first session will be in mid-January. Stay tuned to our Facebook page for more details in the coming days.

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 7:30 a.m. December 31, 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

2014-12-31

Avalanche Advisory for Tuesday, December 30, 2014

This advisory expires tonight at 12:00 midnight.

All forecast areas of Tuckerman and Huntington Ravines have Low avalanche danger. Natural avalanches are very unlikely and human triggered avalanches are unlikely except in isolated terrain features. Unstable snow may exist in isolated terrain features – use caution in these locations.

AVALANCHE PROBLEM: Avalanche problems today are limited to small pockets of wind slab that developed over the past couple days. In both ravines, the overall snowpack is looking rather sparse for the end of December. This means the locations where you may find unstable slab are relatively small and isolated from other areas of snow. This does not mean they are “safe” or that you should leave the beacon, shovel, and probe down in the car. In fact, given the consequences of a fall in the current conditions, any small pocket of unstable snow will be quite dangerous. On the whole, there is a lot of stable snow out there, but don’t let your guard down.

WEATHER: Today is going to be a sunny day on the mountain, albeit cold and windy. I don’t expect today’s winds to have much of an effect on the avalanche conditions. The snow that landed at upper elevations two days ago has largely reached its final destination already, or at least until we see a significant jump in wind speeds. If you are out in the Presidentials today, even just for a hike, be prepared for arctic conditions and gusty winds. Cover up exposed skin!

SNOWPACK: We had been watching the weather closely over the last couple days, mostly because cloud cover on the mountain meant that was all we could see. Yesterday afternoon the clouds broke and Frank and I were able to get into both ravines to see what happened with the 5” of snow that fell on the summit Sunday and was followed by very strong winds. Much to our dismay, it did not appear as though 5” of snow had been loaded in. This could be due to a variety of factors, but the result is the same. We saw areas of old crust, areas of wind-hammered snow, and occasional pockets of slab with a weak layer of unconsolidated snow between the slab and the crust. These pockets were found only in very strong lee areas that were well protected from winds. If there are avalanche concerns out there today, they will be in these isolated pockets. Your best bet for finding them would be in the Lip (where the Tuckerman Ravine Trail crosses above the waterfall), under the ice in the Center Bowl, or perhaps in the middle section of Central Gully. Other locations may also harbor this problem, so keep your eyes open as you travel about, but generally you’ll be traveling through snow with good stability.

In other news, the Lion Head Summer Trail remains open and will be the preferred route until we get significantly more snow. The trail does cross an avalanche path in a couple locations, but there needs to be a lot more snow before this becomes a problem. The John Sherburne Ski Trail has fair coverage but is very hard-packed and icy. There are a lot of very abrupt waterbars, open patches of frozen turf, and some water ice. Extreme optimists say it’s still better than walking down, but you may disagree long before you reach the bottom. And finally, we will be resuming the Eastern Snow and Avalanche Workshop (ESAW) Continuing Education Series this winter. The first session will be in mid-January. Stay tuned to our Facebook page for more details in the coming days.

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 30, 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

2014-12-30

 

Avalanche Advisory for Monday December 29, 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 have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Careful snowpack and weather evaluation, cautious route-finding, and conservative decision making are essential.  All other forecast areas have Moderate avalanche hazard. Natural avalanches are unlikely and human-triggered avalanches are possible. Evaluate snow, weather, and terrain carefully.

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger. North, Damnation, Yale, Central, Pinnacle, and Odell have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Careful snowpack and weather evaluation, cautious route-finding, and conservative decision making are essential. South Gully and the Escape Hatch have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow, weather, and terrain carefully.

AVALANCHE PROBLEM: We have the potential for additional snowfall and strong consistent winds leading to the development of wind slab in lee areas. Winds today will remain quite strong, which should allow loading to continue throughout the day. This wind loading and subsequent slab development will keep the snowpack trending toward worse stability.

WEATHER: Since the thaw ended and snow began to fall, Mt. Washington Observatory has recorded 5.1″ (12.5cm) of roughly 11% density snow with winds holding strong from the W and NW. Due to temperature differences, elevations below Hermit Lake received wet snow and rain instead of the snow that landed in the alpine zone. After the bulk of the snow fell, there was a modest lull yesterday afternoon before winds cranked up again to 60-80mph (95-130kph). This morning the strong W and NW winds will continue and there are some snow squalls expected. This may bring another 1-3″ (2.5-7.5cm) of snow to upper elevations.

SNOWPACK: We are still in recovery mode from the Christmas rain event. If we had a full mid-winter snowpack, 5″ of new snow with another 1-3″ on the way, coupled with these winds, would make for pretty simple forecasting and hazard assessment. It would scream “Danger! Danger!” with red lights flashing — or at least that’s how it would look to me. In the current situation, we have a more discontinuous snowpack and smaller bed surfaces. Avalanche tracks and runout paths are less developed. Many locations have numerous anchors still well exposed. The alpine zone in not fully encased in snow, so there are lots of locations for snow to get “trapped” instead of  blown into the ravines. All these factors do contribute to the nature of the avalanche potential being such that we expect relatively smaller sized avalanches and the likelihood of a naturally triggered avalanche falling somewhere on the line between Moderate and Considerable (i.e. unlikely vs. possible.) The primary factors that tipped the scale toward the Considerable ratings include the total amount of snow available for wind loading and the ability of the winds to move large quantities of snow in to the ravines. This data is difficult to ignore. Other factors come into play, such as the lull in winds and slight shifts in direction leading to variations and potential weak interfaces within the new slab. We believe that a savvy traveler who is very observant might be able to thread the needle through the terrain today, but it would not be without risk and uncertainty. If you intentionally seek to find softer snow, you won’t be threading the needle, you’d be sticking yourself right in the thumb with it, as you will be seeking the areas with the same new slab we are concerned about today. With a little luck, visibility will improve late today and more visual clues will help with decision making. Unless this happens, keep in mind that 8″ can translate to a lot of wind slab!

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 29, 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

2014-12-29

Avalanche Advisory for Sunday, December 28, 2014

This advisory expires tonight at 12:00 midnight.

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

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger today. Yale, Central, Pinnacle, and Odell have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely.  Careful snowpack and weather 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. Evaluate snow, weather and terrain carefully.

AVALANCHE PROBLEM: Todays Wind Slab and Storm Slab problem is tied directly to wind speed and direction as well as total snowfall expected today. 2-4″ (5-10cm) of new snow is forecast and the current rate of precipitation at Pinkham and Hermit Lake is raising concerns that we may quickly reach the upper end of the forecast amount. The likelihood of natural avalanches will increase through the day as upslope snow showers accumulate and wind loading continues.

WEATHER:  Anticipate wind loading on east and southeast facing aspects as well as lee areas as wind shifts from the W to the NW at 60-80 mph (95-130kph). Lingering moisture will continue to generate upslope snow showers as the front passes which is creating our stability concerns as well as hamper visibility. Reduced visibility from fog and blowing snow may challenge your ability to assess the extent and size of potential wind and storm slabs. Though temperatures low on the mountain at this hour are allowing a copious drizzle to fall, anticipate temperatures to drop through the day to the lower teens F (-9 to -12C) tonight. Rain/snow line was at around 3700′ at 7:00am.

SNOWPACK: Our snowpack took a beating from recent warm temperatures and rainfall. Melt channels and signs of ice fall peppered the snow surface yesterday. Many areas are likely undermined and many frozen waterfalls are either detached or missing. Due to above average December snowfall, there remained ample bed surfaces in leeward slopes like Central Gully, Sluice, the Lip, Chute and Left. While certain factors  lead me to believe that we may not reach a Considerable rating, I wouldn’t bet my life on them. Warm incoming snow on a fairly coarse bed surface with abating winds may yield fair stability from a right side up slab configuration and reduce the likelihood of natural avalanches from possible to unlikely. Coupled with discontinuous bed surfaces in many areas like Center Bowl we may make it through the day without natural avalanche activity. Though our avalanche character may end up being on the small side, the nature of our terrain makes the outcome of an avalanche as dire as ever. The consequences of making the wrong stability assessment above rocky cliff bands and frozen waterfalls such as the Lip while on the Tuck trail, or anywhere in Yale or Pinnacle would be catastrophic. Other areas with larger potential bed surfaces like Central Gully or Chute will make the potential for a larger avalanche more likely and make the Considerable rating feel much more accurate if you find yourself in or below this terrain. Today is a day when you’ll want to use all of your strongest weather observation and snowpack evaluation skills if you venture into avalanche terrain.

Please Remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
  • Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
  • For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.
  • Posted 8:20 a.m. December 28, 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

2014-12-28 print friendly

Avalanche Advisory for Saturday, December 27, 2014

This advisory expires tonight at 12:00 midnight.

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

AVALANCHE PROBLEM: The potential for isolated areas of Wind slab should be remembered today, but generally this should be a remote issue.  Since the thaw and rain on Tuesday and Wednesday we have only picked up a meager amount of new snow.  This may have given us a pocket or two behind some terrain features, but high winds have kept most areas scoured clean.  The water saturated snow from Wednesday has been re-freezing deeper each hour as cold air temperatures remain in place.  This continues to create a bridging eggshell over the snowpack causing any deep weaknesses to be inconsequential. Place your focus on new developing instabilities that may occur on top of the crust during upcoming precipitation events, such as tonight’s snow showers.
WEATHER: Yesterday, very high winds continued to pound the hill, peaking at 112mph (180kph).  Speeds have trended downward and the current winds, gusting to 75mph, are forecasted to continue falling to 30-45mph later today.  Expect sunshine and some clouds to give us a fairly reasonable day in the mountains.  Tonight snow showers will return expected to deliver 1-3″ (2.5-7.5cm) by Sunday morning.  This will be the first snow on the mountain since Thursday’s 0.4″ (1cm).  Winds will also increase once again, exceeding 100mph (160kph) from the W tonight and into tomorrow.  Temperatures will start moving down again, perhaps hitting 0F (-18C) Sunday night and early Monday morning.  Expect a very cold week ahead with temperatures deep into negative F territory.

SNOWPACK: The freewater from Wednesday’s wet event has been freezing from the surface down for about 48 hours. Snow temperatures will continue to fall with cold ambient air in place freezing and bonding round wet grains deeper by the hour. As already mentioned, this creates a bridge over any deeper weaknesses due to its strength.  Additionally, we have thin early season coverage so the freezing upper snowpack is also held in place by freezing around brush, trees, poking cliffbands, and rock anchors.  We’ll watch, as should you, for faceting/recrystalizing that will likely occur this week with very cold air settling in.  However, continued moderate to high wind speeds should keep this process from occurring too rapidly.  In the meantime, the big issue is more the slick surfaces that exist. As discussed yesterday, the current icy snow surface will lend itself more to a bobsled run than arresting a fall with an axe easily.  If a slip does cause a fall, an immediate self arrest is absolutely critical due to the potential for Mach speeds in a blink of an eye.  Unfortunately, history has shown that sliding falls into the rocks below is the most frequent accident when we have slick surface conditions. Microspikes and trekking poles are helpful on very low angle trails approaching the Ravines, but have no place in steep terrain.  Crampons, an ice ax, and the skill to use them effectively are all needed to travel safely on the upper mountain.  Ice climbers should expect the potential for ice dams struggling to hold back water pressure beneath the ice.  This is most common in narrow gullies, but is also common near bulges in more open terrain.  These have a history of causing accidents as their pressure becomes released by a swinging ax placement.  It goes without saying, but I’ll mention it anyway. Expect the Sherburne ski trail to be very challenging with hard rough terrain.

Please Remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
  • Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
  • For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.
  • Posted 6:50 a.m. December 27, 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

2014-12-27