Avalanche Advisory for Tuesday, February 28, 2017

This advisory expires at Midnight.

Huntington Ravine and Tuckerman Ravine have LOW avalanche danger. Natural and human-triggered avalanches are unlikely in all forecast areas. Watch for unstable snow on isolated terrain features. The Little Headwall is no longer forecast this season as it is now an open river.

AVALANCHE PROBLEM: The avalanche problem today will be Wind Slab. This formed Saturday into Sunday on S shifting to W winds and can be located primarily under rollovers in the steepest terrain or in sheltered locations from west winds. With up to an inch of snow today, this wind slab may grow in size, however this increase should be negligible in affecting its stability. As this advisory expires at midnight, precipitation should turn to rain. With this changeover in precipitation, this wind slab will become saturated and become a Wet Slab problem. As the snowpack beneath saw 5 days straight of above freezing temperatures last week, the rain should only snow that has fallen since Saturday.

WEATHER: Winds are currently from the west at 40mph with temperatures in the upper teens. Temperatures should increase through the day as the cloud layer lowers and winds shift to the SW. An approaching warm front will bring moisture to the mountains this afternoon with up to an inch of snow before transitioning to rain around midnight. Rain tomorrow should provide an opportunity to stay inside and break out your edge file for the approaching cold snap this weekend.

SPRING HAZARDS: With the warm spell last week, springtime hazards have emerged early this year. Recent cold temperatures have mitigated some of these hazards (icefall) and increased others.

  • The refrozen snowpack is a prime surface for a long, sliding fall. Self-arresting will be very difficult, meaning climbers may want to consider breaking out the rope on your approach.
  • Ice dams – water flowing down Huntington gullies can build up pressure behind ice and burst naturally or more likely from the whack of an ice tool or crampon.
  • Glide cracks, moats and crevasses have opened in places and are now concealed with the new snow making locating these a challenge. The largest ones at the moment at under the cliff that separates the Sluice from the Lip, at the top of the early season ice climb called the Open Book, and on the approach to Central Gully near the climb called Cloudwalkers.
  • Undermined snow over stream channels can be a problem in gullies but more of a danger lower in the tributaries. The generally warm winter so far hasn’t allowed many streams to freeze so this undermining is emerging early this year. The Little Headwall is mostly open water, making exiting the Bowl on skis difficult.

Please come join us this Thursday, March 2 at Allspeed Cyclery and Snow in Portland for an evening with your avalanche forecasters. Our new Director, Frank Carus, will be talking about some of the changes going on within the avalanche center and how you can help make a difference. This event will be hosted by Friends of Tuckerman Ravine and will also feature one of New England’s own, Ben Leoni. You may know Ben from his film series Working for the Weekend produced by Ski The East. Ben will be talking about his time skiing in Quebec before we launch the most recent episode onto the big screen. This will be a great opportunity to meet our newest forecaster, Ryan Matz, as well as get a chance to socialize with people who love nothing more than talking about 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  7:50 a.m., Tuesday, February 28, 2017. A new advisory will be issued tomorrow.

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

2017-02-28

Avalanche Advisory for Monday, February 27, 2017

This advisory expires at Midnight.

 Huntington Ravine and Tuckerman Ravine have LOW avalanche danger. Natural and human-triggered avalanches are unlikely. The Little Headwall has returned to being a waterfall.

 AVALANCHE PROBLEM: Night before last, 2” or so of new snow created thin wind slabs in lee terrain. An inch or so of new snow may add to this problem later today. These pockets are unlikely to pose a problem in most areas but keep an eye out for thicker deposits drifted in behind the shelter of steep areas or at rollovers. The predominately icy snow surface is the more pressing concern. Firm snow will make for great cramponing on steep terrain, but refrozen boot tracks and glide cracks filled in with new snow create pretty nasty trip hazards. Arresting a fall with an ice axe on icy slopes only happens in the movies so travel carefully and consider using a belay and protection early on. Climbs in Huntington, especially northern gully climbs, took a real beating during the thaw. Be on the lookout for ice dams. In Tuckerman Ravine, melt channels mar the surface and the main waterfall is flowing near the Lip with a hole now open downslope at the top of the Open Book. This could become thinly bridged over by drifting snow.

WEATHER: West winds in the 60-80 mph range with higher gusts this morning will diminish a bit through the day. Temperatures will climb slightly from the current 10F to mid-teens on the summit. All in all, the mountain will see a return of winter conditions today before the next round of warm air moves in tomorrow followed by rain and freezing rain on Wednesday. Fog and low visibility will be a factor later today so don’t be surprised if the window closes this afternoon.

SPRING HAZARDS: With the warm spell last week, springtime hazards have emerged early this year. The cold temperatures over the past 36 hours have made the main hazard long, sliding falls, but be aware of the other usual spring suspects emerging in certain areas:

  • Ice dams – water flowing down Huntington gullies can build up pressure behind ice and burst.
  • Glide cracks, moats and crevasses have opened in places and are now concealed with the new snow, making identifying these extra difficult.
  • Falling ice and rocks become more frequent and sometimes larger as bonds holding things in place release.
  • Undermined snow over stream channels can be a problem in gullies but more of a danger lower in the tributaries. The generally warm winter so far hasn’t allowed many streams to freeze so this undermining is likely to emerge early this year. The waterfall has re-emerged in the Little Headwall and creeks are as open as they are bridged over with 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  8:15 a.m., Monday, February 27, 2017. 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

2017-02-27

Harbingers of Spring

At the start of last week, the snow depth at Hermit Lake was 209cm. This morning, the height of snow (HS) is down to 163. This is a significant drop. In my mind, two things above Hermit Lake are signs that spring is on its way. The first is when the Little Headwall reopens and prevents skiing out of the Bowl. The second is when the waterfall hole next to the Lip opens. See the pictures for signs that spring is closer than I would like to think in late February.

Looking at the Bowl from Hermit Lake on the afternoon of February 26.

The Little Headwall. The visible water is the only exposed water on the steep section. Getting to this from above also involves navigating open water holes. It is possible to ski the trees to lookers left of the Little Headwall as well as the drainage to lookers right of the open water. Keep in mind getting to both of these options may involve some “mixed” skiing.

The waterfall hole in the Lip has opened. This will gradually grow in size and creates an additional hazard for steep skiing in the Bowl.

Avalanche Advisory for Sunday, February 26, 2017

This advisory expires at midnight.

Huntington Ravine and Tuckerman Ravine have LOW avalanche danger. Natural and human-triggered avalanches are unlikely in all forecast areas. Watch for unstable snow on isolated terrain features.

AVALANCHE PROBLEM: Wind Slab will form today from snow showers last night as well as likely continued upslope snowfall today. The hazard will increase as snow accumulates, but with 1.5” last night and up to another inch expected today, the unstable areas will be pockets on isolated terrain features large enough to cause a long, sliding fall. The area of main concern today for wind slab would be just under the rollover in the Lip, Center Bowl and Chute.  Across much of our terrain, a non-avalanche hazard that is real and present today is this possibility of long, sliding falls. Overnight, our snowpack went from wet and heavy to a skating rink. Acuity with crampons and an ice axe will be crucial to making it down safely at the end of the day.

WEATHER: Above freezing temperatures for several days has come to an abrupt end. The thermometer dropped below freezing on the Summit last night around 9pm and is now at 5F. Precipitation began yesterday afternoon with several hours of drizzle and light rain before transitioning to graupel and then snow. The Summit recorded 2.3” of snow with a trace falling at Hermit Lake. This morning, upslope snow showers should bring up to an inch of snow. Winds will be strong (55-75mph) and from the west. Tonight will remain cold with winds increasing slightly and skies clearing.

SNOWPACK: Over the past five days, the Summit recorded only two hourly temperature readings below 32F, the rest being above freezing. This is evident by looking at the snow stake at Hermit Lake which has lost 46cm (18”) of snow in that period. This snow loss can also be seen by the looking at the rivers that cross the trail. Five days ago these offered good skiing while many are now open water including the Little Headwall which will require careful navigation of a waterfall to descend (it may be better to try the tree skiing to either side of the main streambed). With the drop in temperature last night, the wet snowpack is refreezing. This refreeze will eventually lock up the snowpack into concrete. On top of this firm snowpack will be new snow from last night and today. Strong winds will scour some locations and create the aforementioned wind slab in the steeper terrain. This morning, travel on trails and areas that have seen traffic is firm and requires traction. As lower elevations have only recently dropped below freezing, traveling off-trail in the woods will likely still result in postholing for much 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., Sunday, February 26, 2017. A new advisory will be issued tomorrow.

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

2017-02-26

Avalanche Advisory for Saturday, February 25, 2017

This advisory expires at Midnight.

 

Huntington Ravine and Tuckerman Ravine have LOW avalanche danger. Natural and human-triggered avalanches are unlikely in all forecast areas. Watch for unstable snow on isolated terrain features.

AVALANCHE PROBLEM: Today’s avalanche problem will be loose wet slides. These will primarily be skier triggered and while slow moving, they can be tough to escape once entrained. These can be triggered anywhere, but will be a bigger problem in areas that have not seen traffic recently as there is more loose snow available. Wet Slab avalanches are unlikely. Our snowpack has had several days to adjust to the warm temperatures, but with possible record-setting temperatures today combined with more than half an inch of rain tonight, we may see a deep layer lubricate enough to release. This would be most likely in an area that already has water running through it. The waterfall hole in the Lip is an area that potentially could burst open and cause a deep slab release with the right conditions.

WEATHER: Currently, the temperature on the Summit is 37F with a SW wind at 35mph. Hermit Lake is at 46F. Temperatures may increase slightly through the afternoon before falling significantly tonight, reaching close to single digits F by daybreak tomorrow. Occasional rain may fall today, but it seems that most of the rain will fall after dark, with up to ¾” of water, before changing over to snow. With plenty of moisture in the air, most of the terrain will likely remain in the fog today.

SPRING HAZARDS: Our snowpack has been warming for over 72 hours. Springtime hazards are emerging and will likely play a larger role than the avalanche hazard today. Pay particular attention to

  • Ice and Rock fall: Several ice climbs in the valley collapsed during the warm spell. Higher elevations are heading this way. Be aware of what hangs above when traveling around the mountain, particularly in the Lunch Rocks area.
  • Undermined Snow: Runoff is raging at the moment with flood warnings issued through tomorrow. Areas like the Little Headwall and other rivers are eating away at the snow from beneath. New holes are opening constantly in streambeds.
  • Glide Cracks and Crevasses: The snowpack is slowly moving downhill and pulling away from cliffs and rocks, creating holes in the snowpack. With heavy fog today, these may be difficult to see.
  • Ice Dams: Lots of water is flowing today. The pressure that this can create when dammed behind an ice flow can cause things to burst naturally or from an ice tool placement
  • Long Sliding Falls: Unlikely today, these will be the main hazard tomorrow. With the temperatures plummeting tonight, expect the snowpack to freeze into concrete. If recreating tomorrow, make sure your crampon and ice axe skills are sharp.

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  8:05 a.m., Saturday, February 25, 2017. A new advisory will be issued tomorrow.

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

2017-02-25

Avalanche Advisory for Friday, February 24, 2017

This advisory expires at Midnight.

Huntington Ravine and Tuckerman Ravine have LOW avalanche danger. Natural and human-triggered avalanches are unlikely.

 AVALANCHE PROBLEM: Skier triggered wet-loose avalanches will be the primary avalanche problem today though other emerging spring hazards will pose an equal or greater danger. Loose but heavy sluffs of snow kicked up by a skier can be challenging to deal with at times so be mindful of this hazard, especially if venturing into areas with a sunny aspect or an area that’s not been ridden recently. Though the prolonged heat wave has generally allowed weaker layers in our snowpack to settle and bond, wet slab avalanches are a greater possibility today as water travels deeper into the snowpack. The Lip waterfall often flows onto an ice layer within the snowpack resulting in a wet slab avalanche during early spring thaws with rain. Today’s record warmth and rain in the afternoon will increase the potential for this sort of avalanche activity in our forecast area.

WEATHER: Continued warm temperatures last night did not refreeze the snow at our forecast elevation. Temperatures will continue to rise from where they stand at 32F on the summit and 46F at Hermit Lake, ultimately reaching 40F on the summit. Partly cloudy skies this morning will give way to more clouds as a warm front arrives around noon. NWS forecast models are calling for up to a ¼” of rain this afternoon which will only add to the melt water flowing in the snowpack due to warm air temperatures. Southwest wind will diminish a bit to 30-45mph before increasing again to 50-70 mph as the warm front arrives in the afternoon.

SPRING HAZARDS: Sloppy wet cement was one description I heard for the snow yesterday. Without a freeze last night, similar conditions will prevail today with firm surfaces in some areas. Due to the late arrival of our typical January thaw or early taste of spring, the following hazards should begin to appear on your radar.

  • Ice dams – water flowing down Huntington gullies can build up pressure behind ice and burst.
  • Glide cracks, moats and crevasses are beginning to open a bit and may grow larger as things warm.
  • Falling ice and rocks become more frequent and sometimes larger as bonds holding things in place release.
  • Undermined snow over stream channels can be a problem in gullies but more of a danger lower in the tributaries. The generally warm winter so far hasn’t allowed many streams to freeze so this undermining is likely to emerge early this year. The waterfall has re-emerged in the Little Headwall, along with the rocks until recently covered in ice, and is indicative of this problem.

Eight days ago, there was 94” of snow at the Hermit Lake snowplot with 75” this morning. Though we still have really good coverage, expect one more warm day tomorrow with up to an inch of rain before freeze up on Sunday.

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  8:03 a.m., Friday, February 24, 2017. 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

2017-02-24

Avalanche Advisory for February 23, 2017

This advisory expires at Midnight.

Huntington Ravine and Tuckerman Ravine have LOW avalanche danger. Natural and human-triggered avalanches are unlikely.

 AVALANCHE PROBLEM: Skier triggered wet-loose avalanches will be the primary avalanche problem today though other emerging spring hazards will pose an equal or greater danger. Loose but heavy sluffs of snow kicked up by a skier can be challenging to deal with at times so be mindful of this hazard, especially if venturing into areas with a sunny aspect or a previously unskied area. Several warm days have allowed our snow to adapt to the heating through settlement of the layers of snow, making a deeper wet slab avalanche only a very remote possibility.

WEATHER: Summit temperatures have remained above freezing for the past 24 hours with our forecast areas above freezing for a couple of days now. In the past six hours the temperature has been 34F on the summit with the mercury at 41 currently (at 7:30am) at Hermit Lake. A warm front developing over the region will allow southwest flow to continue today. The degree to which temperatures will rise is a little uncertain due to cloud cover and limited mixing in the atmosphere. Add to this a deep and cold snowpack and calm winds allowing for cold air to settle through the valleys, and you have a recipe for a jambalaya of surface conditions. Suffice it to say that early spring conditions will be on tap even with the forecasted cloud cover. Expect W winds at 30-45 mph increasing to 65-85 mph later. Temperatures on the summit will reach the upper 30’s with even warmer temperatures in the Ravines.

SNOWPACK: Postholing in one gully with firm conditions in another will make it a smart idea to have a flexible itinerary. Snow temperature 20 cm down is -1.5C at Hermit Lake so anticipate firm surface conditions in areas of firm old wind slab on shady aspect. Softer snow and sunny aspects will likely allow much deeper boot penetration outside of existing bootpacked trails. A harvest of corn is likely on most aspects. The warm temperatures have begun to open glide cracks so beware of moats near rocks and opening cracks mid-slope. Due to the generally warm winter conditions, streams have remained mostly unfrozen so punching through into water may be possible in thinly bridged areas. Spontaneous rock and ice fall are also possible today as ice loosens its grip and becomes plastic. While probably not a large or widespread problem yet, be choosy as to when hanging out or taking your helmet off will be a good idea.

Seven days ago, there was 94” of snow at the Hermit Lake snowplot with 81” this morning. Things are changing rapidly here.

A week from today,  March 2nd at 6:30pm, Allspeed Cyclery and Snow will be hosting a shindig at the Portland store to benefit Friends of Tuckerman Ravine and the avalanche center. A brief presentation from our forecast team as well as raffles and prizes should make for a fun and educational night. Information and tickets available online at http://www.friendsoftuckermanravine.org/allspeed_party with more information available through Allspeed’s Facebook page.

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., Thursday, February 22, 2017. 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

2017-02-23

 

Avalanche Advisory for Wednesday, February 22, 2017

This advisory expires at Midnight.

 

Huntington Ravine and Tuckerman Ravine have LOW avalanche danger. Natural and human-triggered avalanches are unlikely in all forecast areas. Watch for unstable snow on isolated terrain features.

AVALANCHE PROBLEM: A few things to look out for today are areas of Wind Slab as well as the possibility of a Wet Slab. As the day progresses, the chance of a human-triggered wind slab will decrease as the snowpack warms, however this will increase the chances of a wet slab. Pockets of wind slab are isolated and are identifiable by their smooth appearance; they are primarily in the steeper terrain and in lee areas of NW winds. Areas of greatest concern for a wet slab today would be areas that have not seen much traffic and will bear the brunt of the sunshine today. The Sluice fits this category well and also has the added objective hazard of icefall potential today. With warming temperatures, it doesn’t have to be spring to have springtime hazards. Be aware of icefall today and also be on the lookout for settlement cracks beginning to appear.

WEATHER: Warm temperatures, calm winds, and sunshine will dominant the weather for today. Yesterday, the Summit recorded a high temperature of 36F with ample morning sunshine. Currently, it is 30F on top and 37F at 4000’ Temperatures will increase today with some areas likely getting into the 40sF. Winds are currently 33mph from the west and will decrease further along with clearing skies. It will remain warm tonight, likely with much of the mountain remaining above freezing.

SNOWPACK: Overall, our snowpack is stable to start the day. Several slopes, primarily the south-facing slopes like Right Gully, Lobster Claw, Yale, Damnation, and North have experienced some freeze/thaw cycles over the past few days. The warmth has yet to penetrate deep into the snowpack, leaving cold snow beneath the top several inches which are undergoing the daily change. East and north facing slopes, Lip through Left and Central through South have remained primarily unaffected by the diurnal temperature fluctuations. These slopes are made of mostly one-finger to pencil hard snow of varying forms: wind slab and sastrugi interspersed with small pockets of the softer wind slab of concern today. With ambient air temperatures reaching into the upper 30sF along with clearing skies, many slopes will feel significant warming today. While this will help soften the snow and in areas make good traveling, S and SE facing slopes and mini-bowls like the Sluice may warm dramatically. Meltwater running into the snowpack like this on some of the first warm days of the season has been known to do strange things. With this wet slab idea lurking in the background combined with the potential for icefall today, Low avalanche danger today still demands safe travel techniques and identifying hazards on the mountain.

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., Tuesday, February 21, 2017. A new advisory will be issued tomorrow.

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

2017-02-22

Avalanche Advisory for Tuesday, February 21, 2017

This advisory expires at Midnight.

 

Huntington Ravine and Tuckerman Ravine have LOW avalanche danger. Natural and human-triggered avalanches are unlikely in all forecast areas. Watch for unstable snow on isolated terrain features.

AVALANCHE PROBLEM: Pockets of Wind Slab exist in our terrain and will provide the primary avalanche problem for the day. These pockets can be identified by their smooth appearance and are found in lee areas of NW winds. The likelihood of triggering these pockets is small and will decrease further through the day as settlement occurs. With clear skies and ample sunshine today, south facing aspects will soften and may present the problems with loose wet sluff management. This sluff can act like concrete, slow moving and hard to escape once entrained in it. Worth keeping in mind is the large wind slab that formed after our latest avalanche cycle last week. It will likely take more than a human to trigger this slab. The potential trigger out there today could be icefall. With temperatures warming, this possibility should be discussed.

WEATHER: After a week of snow and wind, this past weekend was a preview of the approaching spring. While temperatures remained largely below freezing up high, sunshine allowed snow to soften on south-facing aspects. Approximately an inch of snow on Sunday blew in on NW winds. High pressure today will create clear skies, mild winds, and temperatures into the mid-30sF. Clouds may develop in the afternoon along with a slight chance of mixed precipitation.

SNOWPACK: The snowpack encountered today will depend on what aspect the slope is facing. South facing slopes felt the effect of the sun over the past few days and are in the midst of a melt-freeze cycle, likely forming corn snow in areas today. SE slopes are beginning to metamorphose too, although these slopes have not felt as much sun and are just beginning the cycle. Skiers yesterday in the Sluice reported alternating turns on cold snow and sticky snow, highlighting the change that slope aspect can create. Keep in mind it is still February and the days are relatively short; many areas in Tuckerman and Huntington are still only seeing brief periods of escaping the shade of the neighboring ridges. East through north facing slopes have stayed cold, allowing the snow to stay dry in its various forms. Expect scoured old surface, firm sastrugi, and pockets of the snow from Sunday that has since formed wind slab. The wind slab will provide the softest cold snow but also harbors the greatest (albeit unlikely) instability 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., Tuesday, February 21, 2017. A new advisory will be issued tomorrow.

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

2017-02-21

Avalanche Advisory for Monday, February 20, 2017

This advisory expires at Midnight.

Huntington Ravine and Tuckerman Ravine have LOW avalanche danger. Natural and human-triggered avalanches are unlikely in all forecast areas. Watch for unstable snow on isolated terrain features.
AVALANCHE PROBLEM: Our snow pack has refrozen on southern aspect which had seen some softening over the weekend. After prolonged NW winds in the 50-80 mph range, some snow was still being transported into our start zones in a limited way yesterday afternoon. Around a half inch of new snow added to the total amount available last night. Small pockets of soft wind slab will be the primary avalanche problem. Reloaded lee areas in the Sluice through Chute area following our last avalanche cycle is the area of most concern for larger, lingering wind slab. Though unlikely to be triggered by a skier or climber due to the strength and bridging power of these slabs, this would be larger than the pockets of new soft wind slab on the surface.
WEATHER: Northwest winds will continue to diminish and shift north. Currently in the 45-60 mph range, the wind will diminish a bit to 35-50 mph by this afternoon. Temperature on the summit is currently 5F but will rise to the mid-teens through the day. Summit fog should clear later this morning with partly sunny skies and good visibility through the afternoon.
SNOWPACK: Field observations over the weekend revealed that snow had softened a bit on Saturday in a few sun exposed areas. Generally, though, the snow remained cold and dry in our forecast areas despite the warmth of the ambient air temperature. The exception is the gullies with a strong southern aspect where a very thin breakable crust less than a 1cm thick now likely exists on areas of softer snow. Right Gully, which was the target of many skiers on Saturday, had a quite variable snow surface yesterday and was not particularly attractive for skiing. The thin melt/freeze crust would likely go unnoticed on smoother slopes of firmer wind slabs. Significant settlement (7cm on Saturday morning, 7cmSunday and 3cm this morning) was recorded at Hermit Lake due to the warm temperatures. This settlement is driving down our avalanche danger along with falling temperatures. This refreezing effect will be most noticeable at lower elevations where packed snow on trails is now hard and refrozen. You’ll also encounter deeper snow and challenging travel in wooded areas along with large drifts of deep snow above treeline.

 

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., Monday, February 20, 2017. 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

2017-02-20