Avalanche Advisory for Wednesday, March 14, 2018

Huntington Ravine has High and Considerable avalanche danger. Central Gully has High avalanche danger. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. All other forecast areas have Considerable avalanche danger. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential.

 Tuckerman Ravine has High and Considerable avalanche danger. Sluice, Lip, and Center Bowl has High avalanche danger. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. All other forecast areas have Considerable avalanche danger. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential. The Little Headwall is the exception with Moderate avalanche danger.

 AVALANCHE PROBLEM: Wind slab formed from northerly wind will be the primary avalanche problem this morning before wind shifts NW and begins to build new and potentially larger slabs late today. These new layers will all be very sensitive, likely to avalanche naturally and very likely to be human triggered in High rated areas. If that’s not enough to keep you out of the terrain, storm slabs and dry loose sluffing will be secondary problems forming from the snow currently falling on light wind. This number of avalanche problems is compounded by deeper and potentially unstable slabs formed late last week in much of the terrain. You’re likely to trigger an avalanche in essentially all forecast areas today, and avalanches could be quite large. It’s a great day to enjoy the powder away from avalanche terrain or at the ski area!

 WEATHER: The Nor’Easter arriving yesterday morning has so far brought 16 inches of snow to Hermit Lake, with 9.5 inches recorded on the summit. Snowfall continues currently. Summit wind speed held in the 40-50 mph range while shifting from NE to N during the heaviest snowfall periods which occurred yesterday evening. Wind speeds have diminished since midnight as direction alternated between N and NE to the current 11 mph out of the N on the summit. Snowfall should continue today and be heaviest this morning, with forecasts suggesting another 6-11 inches of accumulation. Summit wind will shift NW and steadily increase to the 30-45 mph range by this evening, with a high temperature in the upper teens and summits in the clouds all day. The big player tomorrow will be NW wind between 50-70 mph holding through the day as snowfall tapers to minimal amounts.

SNOWPACK: The significant snowfall which continues now is rapidly changing our upper snowpack. The northerly wind late yesterday blew with speeds likely to build soft and very sensitive slabs in lee and cross loaded terrain. Particularly sheltered areas could exhibit barely cohesive snow which acts more like a storm slab. This new snow continues to fall and will be transported by wind in greater amounts late today as NW winds approach 50 mph and move snow from our primary fetch zones into the Ravines. Several layers of varying hardness though relatively soft (1F-4F) wind slab formed since late last week lie on the old icy snow surface that previously dominated our terrain. These older wind slabs have gained some stability but shouldn’t be considered stable in our steep terrain. They still could release in a step-down fashion from an avalanche initiating closer to the surface or from continuing added weight of new snow. The exception to this are the few areas that were scoured to the old icy snow prior to this storm, especially upper Left Gully in Tuckerman and Odell Gully in Huntington. Additionally, significant graupel pooling Sunday, in isolated pockets primarily below water ice, is likely to act as a weak layer in these select locations. It’s safe to say that this complexity in our recently formed upper snowpack will challenge your ability to assess it.

 The Harvard Cabin will be open all nights this week.

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 Harvard Cabin.
• Posted 7:40 a.m., Wednesday, March 14, 2018. A new advisory will be issued tomorrow.

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

2018-03-14

Avalanche Advisory for Tuesday, March 13, 2018

Huntington Ravine will reach High and Considerable avalanche danger. Central Gully will reach High avalanche danger. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. All other forecast areas have Considerable avalanche danger. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential.

 Tuckerman Ravine will reach High and Considerable avalanche danger. Sluice, Lip, and Center Bowl will reach High avalanche danger. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. All other forecast areas have Considerable avalanche danger. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential. The Little Headwall is the exception with Low avalanche danger.

 AVALANCHE PROBLEM: Our primary avalanche problem will be very sensitive wind slab developing from today’s storm with instability peaking late today. East winds will shift N as snowfall intensity increases through the day. We expect greatest loading in High rated areas. Natural avalanches are likely and human triggered avalanches are very likely in these areas, and all would be large. Considerable areas are rated as such for two distinct reasons. We expect to see less loading in more windward terrain like Chute, Left, and Hillman’s Highway in Tuckerman and Odell, South, and Escape Hatch in Huntington. Alternately, Lobster Claw and Right Gully in Tuckerman as well as North, Damnation, and Yale in Huntington will receive direct wind loading but aren’t capable of producing a truly large avalanche due to less existing snow in avalanche start zones. A secondary avalanche problem today is older but still touchy wind slabs which exist in most of our terrain. These layers are a concern this morning, prior to new slab development, and could also provide step-down potential for avalanches late today. Avoiding these avalanche problems will be difficult to impossible today. Remember that the relatively smaller human triggered avalanches likely in Considerable rated areas can still have fatal consequences.

 WEATHER: Benign weather yesterday is giving way to the strong Nor’Easter which is already bringing snow in light amounts to the mountain. Snowfall intensity will ramp up to heavy amounts this afternoon which will continue into the night. Accumulation looks to be at least 12-18 inches by midnight tonight. Wind is forecast to increase similarly while shifting from E to N and blowing at a sustained 50-70 mph on the summit late today before diminishing tonight. Temperatures will hover in the teens F on the summit. Snowfall is forecast to continue in lighter amounts tomorrow. Another 3-5 inches should fall during the day as wind remains lighter shifting NW.

SNOWPACK: Our upper snowpack has changed dramatically with multiple storms in the past week and will continue to with the current storm. The icy old snow surface initially resisted bonding with new snow, creating a mix of scouring and pockets of wind slab. The Saturday/Sunday storm finally allowed significant and widespread slabs to develop on the icy old snow. Only a few areas of old surface existed leading into the current storm, particularly in upper Left Gully in Tuckerman Ravine and Odell Gully in Huntington. Most of our terrain holds multiple layers of varying hardness though relatively soft (1F-4F) wind slab which has been reactive in stability tests. Though gaining strength, these existing layers continue to pose stability concerns. Small avalanches in the new snow could step down to deeper layers, or the additional weight (1” SWE) of new snow today could similarly trigger avalanches in the existing snowpack. A more isolated concern is heavily rimed snow and graupel which fell on Sunday and has collected in select areas, particularly below water ice. These snow grains lack cohesion and are likely to act as a weak layer in their select locations. New snow and E becoming N wind today will certainly build thick and sensitive slabs in areas receiving maximum loading.

The Harvard Cabin will be open all nights this week.

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 Harvard Cabin.
• Posted 8:10 a.m., Tuesday, March 13, 2018. A new advisory will be issued tomorrow.

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

2018-03-13

Avalanche Advisory for Monday, March 12, 2018

Huntington Ravine has Considerable and Moderate avalanche danger. Yale, Central, Pinnacle, South, and Escape Hatch Gullies have Considerable avalanche danger. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential. North, Damnation, and Odell Gullies have Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern.

 Tuckerman Ravine has Considerable and Moderate avalanche danger. Right Gully, Sluice, Lip, Center Bowl, Chute, and Hillman’s Highway have Considerable avalanche danger. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential. Lobster Claw, Left, and the Lower Snowfields have Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern. The Little Headwall is rated Low due to a less developed snowpack.

 AVALANCHE PROBLEM: Wind slab formed in the past two days covers most of our terrain and is our primary avalanche problem. These smooth surface wind slabs were formed by W to NW wind which either directly loaded or cross loaded most forecast areas. In many areas, this somewhat soft but cohesive surface snow overlies slabs formed late last week that are similar if a little less soft in character. We expect all smooth surface snow to be sensitive to a human trigger today. The connected and consistent nature of wind slab means that such avalanches could be quite large. Upper portions of Left Gully and most of Odell have heavily wind textured snow at the surface that will be fairly hard and more stubborn to a human trigger, hence their Moderate rating. One if not two natural avalanches in Lobster Claw yesterday have reduced snow available to avalanche, though sensitive pockets likely still exist. Moderate avalanche danger means that human triggered avalanches are possible, suggesting that you should evaluate snow and terrain carefully prior to committing to a slope. It’s not likely you’ll be able to avoid the avalanche problem in Moderate rated terrain today. It’s a beautiful day to enjoy the mountains, so carefully evaluate all snow and terrain. Choose to come home safely.

 WEATHER: Yesterday we picked up nearly 1.5” of 10% snow at Hermit Lake with over 3” recorded on the summit, while the winds out of the WNW decreased steadily overnight. Today we expect summit wind to stay relatively light but shift in direction to the E, increasing to 15-30 mph this afternoon and 30-50 mph overnight.  The incoming low pressure system will bring cloud cover to our currently clear skies with snow expected to start this evening.  The storm should begin slowly then escalate quickly early tomorrow morning.  As the snowfall increases so should the winds, shifting from the E to the N and increasing to 50-70 mph with gusts to 80.  This system is expected to bring 12”-19” to most summits with some areas closer to 24”.  There is a winter storm warning in effect from 4am Tuesday to 2pm Wednesday.

SNOWPACK: The sustained W and NW wind over 70 mph late Saturday was followed by lighter wind yesterday and created wind slabs with some variance in character. More sheltered areas which had lighter loading have relatively soft (4F+) slabs while areas receiving more direct loading likely hold slightly less soft (1F-4F) wind slabs. That said, the surface snow in our terrain is remarkably similar in appearance and is well connected. This cohesive surface snow overlies slabs formed earlier last week that are similar if a little less soft in character. Beneath this new slab or combination of recently formed slabs is the old ice crust that could ultimately be a bed surface for avalanches initially releasing on this layer or nearer to the surface and ultimately stepping down. Weather today should not place additional load on the snowpack, making natural avalanches less likely, but a human triggered avalanche remains likely in much of our 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 Harvard Cabin.
• Posted 8:10 a.m., Monday, March 12, 2018. A new advisory will be issued tomorrow.

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

2018-3-12

Avalanche Advisory for Sunday, March 11, 2018

Huntington Ravine has Considerable and Moderate avalanche danger. Central, Pinnacle, Odell, South, and Escape Hatch Gullies have Considerable avalanche danger. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential. North, Damnation, and Yale Gullies have Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern.

 Tuckerman Ravine has High and Considerable avalanche danger. The Lip and Center Bowl have High avalanche danger. Very dangerous avalanche conditions exist. Travel in avalanche terrain is not recommended. Lobster Claw, Right Gully, Sluice, Chute, Left Gully, and Hillman’s Highway have Considerable avalanche danger. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential. The Lower snowfields is rated Moderate and the Little Headwall is rated Low due to a less developed snowpack.

AVALANCHE PROBLEM: Wind Slab formed in the past 24 hours is our primary avalanche problem, with older wind slabs from our recent successive storms adding complexity to the upper snowpack. Significant snowfall yesterday combined with westerly winds to transport significant snow into lee terrain and cross load other areas. The resulting wind slabs will vary in hardness and could be large. Expect them to be reactive to a trigger. Human triggered avalanches are very likely in High rated areas. Peak instability likely occurred last night, but we don’t expect these slabs have gained much strength since then. Two known close calls occurred yesterday, including a skier caught and carried in Gulf of Slides by an avalanche that occurred while the party ascended.  Shortly after, two skiers were knocked off of their feet at the base of Hillman’s Highway by a natural avalanche. The Hillman’s avalanche is a reminder that low angle areas in our terrain, especially the floor of Tuckerman Ravine, are in the runout of steeper terrain above and should be treated as avalanche terrain. Moving one at a time and carrying avalanche rescue gear is important.

 WEATHER: Yesterday brought continuous and often heavy snowfall, totaling over 9” at both the summit and Hermit Lake. Wind blew out of the W with a few brief shifts NW, increasing through the day with peak summit gusts over 80 mph in the evening. Both wind and snowfall tapered overnight to the current light snow showers and W summit wind of 50 mph. Another 1-3” of snow is forecast today as wind decreases by this evening to under 30 mph out of the NW. We may see another trace to 1” of snow tonight and likely no snowfall tomorrow as wind remains below 30 mph.

SNOWPACK: Winter is back in a big way. The snowfall wouldn’t let up yesterday as westerly winds ideal for transporting snow out of our primary fetch zones increased through late evening. The old icy crust that snow struggled to stick to last week is certainly still a player in our snowpack, and we expect that new snow is finally building unstable slabs on this crust rather than being scoured away by wind. The extent of slab development versus scouring to this crust is our key uncertainty today, with no visibility to middle and upper avalanche start zones since Friday. The wind slabs formed in the last 24 hours could be quite large and well connected, but there is also a chance that some old surface is exposed. Overall we expect that these recently formed slabs are poorly bonded to the old ice crust. Further, these recent wind slabs are likely not bonded well to snow deposited earlier in the week in many areas. Without visibility into the upper terrain it’s wise to travel as if our upper start zones hold large slabs capable of avalanching naturally and running a long ways.

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 Harvard Cabin.
• Posted 8:20 a.m., Sunday, March 11, 2018. A new advisory will be issued tomorrow.

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

2018-3-11

Human-triggered avalanches, Hillman’s Highway & Gulf of Slides

On Saturday, March 10, 2018, two separate avalanche incidents were reported. During the previous 2 days, 14.5″ of snow was deposited at Hermit Lake from a nor’easter and the upslope snowfall that followed. This storm was accompanied by moderate winds that rose to the 60’s mph the afternoon before. Saturday’s advisory called for 4.5″ more snow with increasing wind shifting slightly to the NW. Avalanche danger was rated Considerable in Hillman’s Highway, along with Left Gully and the Headwall forecast zones.

Around mid-day, a party of three talked with a snow ranger on duty who advised that low visibility and continued wind loading made their plan to travel into Hillman’s Highway unwise. The party hiked to Hillman’s and entered the 75′ wide couloir onto a 15-20 degree section of the otherwise steeper runout. Soon after the party returned to the courtyard and reported that everything the snow ranger had cautioned against had played out. Two were struck by debris, knocked down, and carried downslope. Fortunately, much of the energy of the debris flow was absorbed by boulders and holes from a warm spell which reduced our snowpack substantially. When the threat of natural avalanches occurring is elevated, the risks are as well. The natural avalanche that occurred in Hillman’s Highway was much larger and would likely have been unsurvivable.

The same day a party of two skiers set a skin track near the middle gully in the Fingers area of Gulf of Slides, in sparse trees. As the terrain steepened, they began to boot along the left edge of the gully next to the trees. The snow was loose and dry with “no shearing and bonding felt okay”. The first skier had been to this area many times and stayed out of the gully as they made their way towards the rollover near the top. They had spread themselves out as they moved up the slope but paused as they reached the rollover because “something felt wrong”. In moments, the slab failed a “couple hundred feet above” the party and hit both skiers. The first skier was carried but, being on the edge of the gully, he escaped the main flow of debris while the other skier clung to a nearby bush. The skier that was carried turned his beacon to search and could not locate a signal of his partner, who was still above him. Shortly after the caught and carried skier texted for help on his cell phone, the pair made contact and eventually were able to call off the rescue response. The skier who held onto the bush lost his poles while the skier who was carried lost all his equipment though eventually recovered one ski.

Later conversations with the skiers in Gulf of Slides revealed a debate as to whether or not they triggered the slope. They considered it likely that they did not trigger the slope, but rather that it had avalanched naturally. From our perspective, the trigger is relatively unimportant in this instance. If the avalanche had not released while ascending, it is possible that they could have made it to the top and triggered the slope on the way down. In that case, much more of the slab could have been above them with more serious consequences likely. After some reflection, looking at weather data and reading the avalanche advisory, the triggering skier admitted that “overconfidence due to personal experience” in that particular area led him to ignore the obvious red flags that existed due to the snow and weather conditions that day. After the period of warm weather and ice crust which had dominated recent ski conditions, it seems likely that the scarcity heuristic was in play as well. The call of fresh powder is hard to ignore sometimes but it is important to remember that good luck can play a role in good outcomes like this one and luck is one thing no one can count on.

Avalanche Advisory for Saturday, March 10, 2018

Huntington Ravine has CONSDERABLE and MODERATE avalanche danger. Central, Pinnacle, Odell, South and Escape Hatch have Considerable avalanche danger. Dangerous avalanche conditions exist. North, Damnation, and Yale Gullies will have Moderate avalanche danger. Evaluate snow and terrain carefully.

Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. Sluice, Lip, Center Bowl, Chute, Left Gully and Hillman’s Highway have Considerable avalanche danger. Lobster Claw, Right Gully, and Lower Snowfields have Moderate avalanche danger due to a limited snowpack. Heightened avalanche conditions exist on specific terrain features. The Little Headwall has holes in the streambed and thinly covered rocks and ice.

AVALANCHE PROBLEM: Strong wind out of the west and northwest is building wind slabs across our forecast areas. The wind slabs will be largest in areas facing predominately east but will grow large enough to be dangerous in most every forecast area. 4-6” of new snow today will contribute to the growth of these slabs. Moderate rated areas will require careful evaluation and terrain management to avoid triggering a wind slab. Loose dry avalanches will be a problem on and below steep areas. Northern gullies in Huntington melted down quite a bit prior to the recent storms, but a few snowfields remain, so evaluate those areas and protect yourself before committing. The floor of Tuckerman is in the crosshairs of avalanche activity so choose your route carefully if you venture into the bowl. The difference between being struck and buried by a medium versus a large avalanche is only a question of semantics.

WEATHER: A brief weather lull yesterday morning gave way to afternoon snow showers as wind shifted westerly and ramped up to the current 60’s mph on the summit. Overnight, Hermit Lake and the summit recorded approximately 2.5” of new snow. Snowfall continues and is currently heavy at Hermit Lake. Wind will increase a bit while shifting NW before diminishing slightly late tonight. Snowfall today should be around 4” if not slightly more, and we may see another 1-3” tonight. Sunday may bring another trace to 2” of snow as wind continues to decrease. Summit high temperatures in the teens and lows in the single digits are forecast today and tomorrow.

SNOWPACK: The summit picked up 16” of new snow in the past 2 days with 14.5” at Hermit Lake. Most of this snow fell on east winds and was deposited in the flat expanse of the alpine plateau that makes up our fetch zone for wind transport. About half of the new snow from this system fell on light and variable winds which allowed the snow to stick to our slick, refrozen base. Though this icy base has been generally resistant to new snow bonding to it for several weeks now, it seems as if warmer temperatures and lower wind speeds have turned the page. Field work yesterday and ski traffic in Lobster Claw, Right, Sluice, and Hillman’s indicated that the light, dry snow hadn’t developed into slabs, at least not in mid elevation start zones. Steeper areas produced sluffs where snow was sticking in place and evidence of mid-storm sluffing was evident below steep areas.

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 Harvard Cabin.
• Posted 7:55 a.m., Saturday, March 10, 2018. A new advisory will be issued tomorrow.

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

2018-03-10

 

Avalanche Advisory for Friday, March 9, 2018

Huntington and Tuckerman Ravine have MODERATE avalanche danger. All forecast areas have Moderate avalanche danger. Heightened avalanche conditions exist. Evaluate snow and terrain carefully. The Little Headwall has Low avalanche danger with pockets of unstable snow, ice and holes in the snowpack.

AVALANCHE PROBLEM: East winds gusted to 66 mph on the summit yesterday and cross-loaded lee terrain features and scoured other areas of our terrain. A brief period of visibility yesterday allowed a view into Tuckerman Ravine and showed lots of old gray ice crust showing once again. This is an indication of what occurred in Huntington Ravine where you will likely find old surface either showing or just below new snow. This mix of scouring and deposition of new snow in the terrain makes natural avalanche activity unlikely but human triggered avalanches possible. Move one at a time today when poking into new snow and keep an eye on what or who is above or below you. Visibility will be challenging with flat light and snow showers making assessment and safe travel techniques more difficult. New wind slabs are likely to be largest in Lobster Claw and Right Gully and the northern gullies in Huntington due to their lee position. Hillman’s appears to have a more widely distributed 8″ (20cm) storm slab with less wind effect and fair to good stability.                     

WEATHER: Hermit Lake snowplot received 4.3” (11cm) more snow yesterday with 11.5” (29cm) total for the storm. ENE and NE winds, in the 50 mph range on the summit, prevailed during the most intense periods of snowfall night before last. Wind then shifted north yesterday but diminished to the point that not much snow was transported into our terrain. Right now, wind is light and variable. Be on the lookout for signs of wind transport in the afternoon as wind picks up to the 20-35mph range. Northwest winds tonight will ramp up into the range capable of building larger and more dangerous wind slabs. If you have weekend plans that include being in avalanche terrain, know that the forecast wind speed and direction will raise the avalanche danger tonight and tomorrow and build potentially touchy wind slabs in terrain downwind of a northwesterly. 

SNOWPACK: As you may already know, our record warm February brought stability deeper to the snowpack in our terrain. Unfortunately, the ice crust at that surface has been resistant to bonding with new or wind transported snow. This storm seems no different, despite starting out on the warm side. There is no doubt that snow from this storm found purchase in enough areas to cause stability concerns. You’ll want to bring the full arsenal of avalanche rescue equipment and more importantly your snowpack assessment and terrain management skills today, if you choose to get into the terrain. There is uncertainty in the stability of the areas of wind slab that exist in the terrain but the icy bed surface, total snowfall and flat light should prompt a solidly focused level of situational awareness as you move into the terrain.

There is good skiing and riding to be had on the John Sherburne Ski Trail.

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 Harvard Cabin.
• Posted 8:0 a.m., Friday, March 9, 2018. A new advisory will be issued tomorrow.

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

2018-03-09

 

Avalanche Advisory for Thursday, March 8, 2018

Huntington Ravine has CONSIDERABLE avalanche danger. All forecast areas have Considerable avalanche danger. Dangerous avalanche conditions exist.

 Tuckerman Ravine has HIGH and CONSIDERABLE avalanche danger. The Lip and Center Bowl have High avalanche danger. Very dangerous avalanche conditions exist in those forecast areas as well as on the floor of the Ravine. Travel there is not recommended. All other forecast areas have Considerable avalanche danger. Dangerous avalanche conditions exist. The Little Headwall has Low avalanche danger with pockets of unstable snow, open water and holes in the snowpack.

AVALANCHE PROBLEM: New snow overnight plus a 50 mph ENE wind, which is more than capable of blowing new snow into wind slabs, are reason enough to avoid avalanche terrain today. Add 3-7” more snow and a shifting wind  today that will continue to blow snow into our larger avalanche paths and you probably have all the red flags you need to avoid trouble. Wind slab will continue to build today even as wind diminishes and will stress the weak snow below. Though the snowfall totals and wind direction so far don’t indicate particularly large avalanches happening in most places, small and medium sized natural avalanches are likely in many areas and are likely to entrain enough snow to carry and/or bury you. Loose dry avalanches are likely in many locations in Huntington Ravine, especially in northern gullies, Central and Pinnacle. These will be dangerous where they gain a head of steam. Sensitive wind slabs will likely be the primary avalanche problem in other forecast areas.

WEATHER: The nor’easter that is bringing mayhem to the Maine and New Hampshire coast is dousing us with a generous amount of snow water equivalent, with 7.5” of 10% density snow recorded at Hermit Lake at 6:30 a.m. Despite our distance from the coast and the center of the storm, the range continues to wring out snow from this system with light but steady snow continuing this morning. Later today, the center of the low pressure will move back on shore to our north and continue to draw moist air from the ocean through the day and bring continued snow fall before tapering to snow showers tonight. As the low retrogrades, wind will shift with it, continuing to shift from where it began from the east when snow began yesterday, through the ENE where it sits now, ultimately reaching a northwesterly direction by mid-afternoon. This northwesterly wind will be atypically light at 20-35 mph and so won’t dump the massive amounts of snow into the Ravines as these storms usually do, but the wind slabs that formed overnight will continue to be loaded by these winds just the same. Anticipate summit fog and snow to reduce visibility. Summit temperatures will be in the teen’s Fahrenheit.

SNOWPACK: As you have probably already concluded, our upper snowpack is showing many signs of poor stability. The icy refrozen snow that has dominated the surface also locked up deeper layers and has reduced our instability to the new snow from the past 24 hours and possibly a few remaining wind slabs that developed Sunday night and Monday. This storm started out fairly warm but the icy crust has proven resistant to bonding with new snow. There are a lot of variables at play at the interface with the new snow as well as in the new snow layers as wind shifts in speed and direction. You shouldn’t need to dig a pit to find unstable results today but hand shears, small test slopes along with snow and weather history are screaming warning signs pretty loudly.

The John Sherburne Ski Trail will likely see some action today. Snow earlier in the week freshened things up and covered most of the ice and a few rocks. Today’s snow fall will improve conditions further. Enjoy.

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 Harvard Cabin.
• Posted 7:45 a.m., Thursday, March 8, 2018. 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

2018-03-08

Avalanche Advisory for Wednesday, March 7, 2018

Huntington and Tuckerman Ravines have MODERATE avalanche danger. All forecast areas have Moderate avalanche danger. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully to identify features of concern. The Little Headwall does not receive a rating due to lack of snow.

 AVALANCHE PROBLEM: We’re starting the day with pockets of wind slab formed over the past week as our primary avalanche problem, but wind slab and storm slab will develop towards the end of this forecast period which ends at midnight tonight. The pockets of wind slab are the same problem we’ve been referencing all week and have been generally easy to visually identify in contrast with a grey older surface. Though they’ve likely gained some stability, your ability to visually locate these pockets of wind slab will be challenged by new snow and reduced visibility today. The old, icy, and grey in appearance snow surface may prove challenging for incoming new snow to stick to. By late today or tonight we expect the new snow to develop into reactive slabs on this slick bed surface, particularly lower in our avalanche paths where sluffing from higher terrain may deposit snow. Also remember that this old, icy snow surface will easily allow a long sliding fall that would be difficult to arrest.

 WEATHER: Relatively stable and mild weather over the past two days is giving way to the winter storm you’ve surely heard about. Light snowfall is forecast to begin this morning and build in intensity through the day, becoming heavy tonight. 1-3” of new snow should fall before dark today, with 8-12” forecast for tonight and another 3-6” tomorrow. On the summit, SE wind under 30 mph will shift E tonight and peak around 50 mph before slackening slightly and shifting NE by tomorrow morning. Temperatures should remain in the teens F through tomorrow and the storm continues.

SNOWPACK: The old and icy snow surface we continue to talk about will be a key player as avalanche conditions develop from the incoming storm, with no deeper instabilities of concern. Slab building on a slick bed surface will likely occur in some areas while the old surface may remain exposed in others. We’re unsure at this time how well new snow will stick to the old surface for a variety of reasons. Slower wind speeds than might normally accompany a winter storm on Mount Washington could result in minimal scouring, but snow today will likely be light and easily transported by wind. Sluffing will also be a significant factor in slab development, as new snow may sluff off of the steepest portions of slide paths before slabs can build in these areas. These variables affecting slab development and distribution in our terrain will determine the number and size of avalanches we may see, with either many small avalanches or fewer large avalanches being potential outcomes of this storm cycle. Regardless, newly forming cohesive slabs should be reactive on the slick old snow serving as a bed surface.

The Harvard Cabin will be open all nights this week thanks to a fill-in caretaker.

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 Harvard Cabin.
• Posted 8:05 a.m., Wednesday, March 7, 2018. A new advisory will be issued tomorrow.

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

2018-3-7

Avalanche Advisory for Tuesday, March 6, 2018

Huntington and Tuckerman Ravines have LOW avalanche danger. All forecast areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.

 AVALANCHE PROBLEM: Pockets of wind slab remain our avalanche problem as snow struggles to stick to the icy old surface in most areas. Right Gully and Lobster Claw in Tuckerman Ravine have the most continuous new snow which thinly disguises the icy surface and recently formed wind slabs alike. The same Northeasterly wind which did not scour these lee gullies in the past 36 hours resulted in similar conditions in North, Damnation, and Yale in Huntington Ravine. All other forecast areas have significantly more old grey, icy surface exposed. The pockets of wind slab you’ll find throughout the terrain will vary in character but likely remain reactive to a human trigger. Any potential avalanches would be relatively small in size but could knock you off your feet and cause a high speed sliding fall on the icy old snow. This old snow that is hard and smooth is nearly impossible to arrest a fall on, so consider the consequences in terrain you choose and take care to not fall.

 WEATHER: No precipitation and moderate wind speeds yesterday resulted in minimal change to conditions. Today is forecast to bring at least partial clearing of cloud cover as temperatures on the summit approach 20F. Wind will shift from NE to E and remain below 30 mph. These pleasant conditions should persist through tonight before cloud cover, wind, and ultimately snowfall roll back in tomorrow as another Nor’easter approaches. It’s a bit early in the game to commit to forecast snow totals, but we’re optimistic this system will bring more snow than the coastal storm of last weekend.

SNOWPACK: Though we’ve had a few inches of snow in the past week, wind has easily transported it and scoured a majority of our terrain to icy old snow. The multiple melt/freeze cycles which helped form this hard snow surface also stabilized our snowpack, making the pockets of wind slab formed since late last week the only avalanche concern. Avoiding this avalanche problem is straightforward in areas where the grey old snow contrasts the white wind slab, but more challenging in areas like the northern gullies of both ravines where less wind scouring has resulted in less old grey surface. We don’t expect large wind slabs in any terrain. Long sliding falls on the hard, icy old snow remains a key hazard which demands respect. Clearing may allow select sun-exposed slopes to soften slightly but only briefly this afternoon. The current firm conditions which provide good crampon and ice axe travel mean limited options for decent turns, but the John Sherburne Ski Trail has improved and offers decent skiing and riding conditions with a few thin spots.

The Harvard Cabin will be open all nights this week thanks to a fill-in caretaker.

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 Harvard Cabin.
• Posted 6:45 a.m., Tuesday, March 6, 2018. A new advisory will be issued tomorrow.

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

2018-3-6