Avalanche Advisory for Thursday, March 22, 2018

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

AVALANCHE PROBLEM: A low pressure system passing to our south and east may generate 2” of snow today on the mountain. This snow will fall on N and NE winds and may build and cross-load small wind slabs in sheltered locations, particularly northern gullies in Huntington and the right side of Tuckerman Ravine. Any wind slabs that build will be on a very firm, and in most places, smooth snowpack. The hard snow surface will increase the likelihood of triggering a small wind slab and raise the consequences if you were to be surprised or swept off of your feet. If you are playing in steep terrain, an ice axe and crampons will make you feel a lot more secure due to the hard and just barely edge-able snow. Though wind slab may be the primary avalanche problem, a long sliding fall is a close second on the list of hazards.  

WEATHER: It is 20F at Hermit Lake this morning and 16F on the summit with relatively light easterly winds in the 40mph range. Winds will increase to the 50-70mph range as they wrap around to the north through the day. Expect temperatures in the high-teens F on the summit with a chance of snowfall bringing up to 2”, though likely less. Summit fog may obscure visibility at times. Certainly not a bluebird day on tap for this early spring day, but not a bad day to be out and about.

SNOWPACK: It’s been four days since any measureable precipitation fell on the summit, though cool temperatures between 0 and 20F have preserved this new snow well. Sixty-five inches of snow has fallen so far this month on the summit accompanied by colder than normal temperatures, allowing our snowpack to bounce back a bit from the deficit we entered in January and February. There is currently 173cm of snow at the stake at the Hermit Lake snowplot. With a warm and dry pattern in the long-range forecast, who knows how long the snowpack will last. The 30” snowfall last week and the howling 100mph+ westerly wind that followed filled out the slopes and runouts in an impressive way. For now, Tuckerman Ravine is in pretty good shape, though gullies on the right side still have limited coverage despite having enough bed surface to generate avalanche activity there during the last avalanche cycle. Snow surfaces are predominately hard, but pockets of softer snow, some of it covered by a thick and grabby wind skin, exists in sheltered locations like the edges of gullies. This variability will keep you on your toes when skiing or climbing, especially considering the hard surface in most fall lines.

The Sherburne Ski Trail benefited greatly from last week’s snowfall. Great coverage exists, though a bit of scouring may have exposed a rock or two in the usual wind hammered sections.

Be sure to check out our Instagram posts (@mwacenter) for up to date photos and videos. You don’t even need an account to view them online if you are trying to avoid social media!

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., Thursday, March 22, 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

2018-03-22

Avalanche Advisory for Wednesday, March 21, 2018

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

 AVALANCHE PROBLEM: The widespread and firm wind slabs formed late last week are becoming generally unreactive as they gain stability. Isolated and softer pockets may still be touchy to a human trigger. Also consider that solar warming, which could occur today before cloud cover increases, has potential to decrease stability of existing slabs. Low avalanche danger means that both natural and human triggered avalanches are unlikely, but that doesn’t rule out avalanches as a potential concern for your mountain travel. Continue to pay attention to the snow you’re travelling on and plan to travel, looking for signs of instability to identify the isolated pockets that may remain touchy to a human trigger. Travelling one at a time in avalanche terrain is still wise with avalanches unlikely but not impossible.

 WEATHER: High cloud cover will increase through the day following yesterday’s clear skies and moderate summit winds. It’s currently nearly calm on the summit, with easterly wind speeds under 10 mph. This wind will increase through the day, ultimately shifting NE and exceeding 50 mph tonight. The high temperature on the summit should be near 20F. This unsettled weather is the result of yet another Nor’easter, though this system is forecast to largely miss the Presidential range. Snowfall which will begin late tonight and continue into tomorrow could total anywhere from 2-6” as wind eventually shifts N and gusts to around 80 mph.

SNOWPACK: Successive storms late last week built an upper snowpack of layered wind slabs on an old melt/freeze crust. These generally firm slabs are gaining stability and becoming unreactive, though isolated pockets that you could still trigger do exist. It’s worth considering that wind slab is a spatially variable avalanche problem by nature as you choose and move through terrain today. Our snow surface is a mix of smooth and wind textured firm wind slab with the scattered pockets of softer slab that pose a greater stability concern, and is providing enjoyable conditions for skiers and climbers alike. This morning looks to provide a continued nice weather window to enjoy the mountain before clouds and wind increase later today.

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 8:00 a.m., Wednesday, March 21, 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

2018-03-21

Avalanche Advisory for Tuesday, March 20, 2018

Huntington Ravine has MODERATE and LOW avalanche danger. Central Gully has Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern. All other areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.

 Tuckerman Ravine has MODERATE and LOW avalanche danger. Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully to identify features of concern. All other areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.

 AVALANCHE PROBLEM: Wind slab which varies in size and character across the terrain remains our primary avalanche problem. Present in all forecast areas and largest in Moderate rated areas, these slabs should be stubborn to a human trigger but could result in a large avalanche. Cold temperatures which slow bonding between recently formed layers lead us to believe that human triggered avalanches are still possible today, though natural avalanches will be unlikely. Surface snow is fairly firm and supportable in many areas, but softer pockets can be found as well. This spatial variability necessitates careful evaluation of the avalanche problem on your specific route, and that travelling one at a time on and below all avalanche terrain remains appropriate. “Low” avalanche danger does not mean “no” avalanche danger!

 WEATHER: Yesterday’s 60-80 mph NW summit wind has finally begun to diminish. This should continue through the day, possibly to below 30 mph this afternoon. A high of 15F on the summit, compared to -3F yesterday, will combine with slackening winds and generally clear skies to make for a nice day in the mountains. Wind is forecast to shift through N to NE tonight and into tomorrow while increasing slightly. Cloud cover should increase through the day tomorrow, bringing a chance of minimal snowfall late Wednesday and into Thursday.

SNOWPACK: The repeated 100+ mph wind events at the tail end of last week’s storm cycle moved a great deal of snow and left little for our 50-80 mph winds to transport in the past few days. Combined with a widespread natural avalanche cycle, our alpine terrain holds much more snow than it did a week ago. This new snow is generally firm layers of wind slab, with some softer pockets both on and below the surface. These slabs are generally stubborn to a human trigger but are large and well connected in some areas, providing a low probability/high consequence kind of avalanche problem. Particularly cold temperatures which are finally easing today have slowed stabilization of these layers formed at the tail end of last week. Today’s warmer though still below freezing temperatures could result in a brief and minor decrease in stability before ultimately increasing strength of bonds in our upper snowpack. Don’t let your guard down, continue to respect avalanche terrain, and enjoy the milder weather and generally good skiing and climbing conditions.

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 8:00 a.m., Tuesday, March 19, 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

2018-03-20

Avalanche Advisory for Monday, March 19, 2018

Huntington Ravine has MODERATE and LOW avalanche danger. Central Gully has Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern. All other areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.

 Tuckerman Ravine has MODERATE and LOW avalanche danger. Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully to identify features of concern. All other areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.

 AVALANCHE PROBLEM: Wind slab remains our primary avalanche problem today. Generally firm and relatively stubborn to a human trigger, these recently formed surface layers are of most concern in Moderate rated areas where they are particularly large, potentially well-connected, and smooth on the surface. These surface slabs are layered over others formed in the past week, and while we’re not overly concerned with an avalanche initiating deep in the snowpack, it’s worth considering that an avalanche today could ultimately entrain a great deal of snow. It’s a low probability/ high consequence kind of day, with your likelihood of triggering an avalanche not exceeding “possible”. Travelling one at a time through and below avalanche terrain, from safe zone to safe zone, remains a wise and relevant practice on days like today.

 WEATHER: Today is forecast to be a near repeat of yesterday, as high pressure holds a cold air mass over our region. High temperatures on the summit should mimic the -3F recorded yesterday as wind remains NW in the 60-80 mph range until possibly diminishing a little tonight. The current summit fog should give way to clear skies. Tomorrow looks to be a more pleasant day, with temperatures 10 degrees warmer and NW wind decreasing through the day. Increasing high clouds are also forecast tomorrow but we shouldn’t see any precipitation.

SNOWPACK: Cold temperatures which slow stabilization and minimal wind transport in the past 24 hours mean that our snowpack remains much as it was yesterday. The multiple bouts of 100+ mph summit wind since last week’s series of Nor’easters has created largely firm snow conditions. These wind speeds create a great deal of spatial variability in our snowpack, with new slabs of great thickness in some areas while fairly thin in others. Character of these new layers varies accordingly, though we don’t expect sensitivity to a trigger to push beyond “stubborn” in these generally hard slabs. The exception would be small and isolated pockets of softer snow which may remain touchy. Yesterday was the first day of good visibility following our successive storms, and it revealed evidence of widespread mid-storm avalanche activity. Gullies that did not produce an avalanche, if any, were the exception rather than the rule. Of particular note are significant broken trees and avalanche debris just a few feet looker’s right of Connection Cache in Tuckerman Ravine. We don’t believe an avalanche has run to this area in recent years, and it’s an excellent reminder that a large avalanche can threaten flat terrain well below 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 8:00 a.m., Monday, March 19, 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

2018-03-19

Avalanche Advisory for Sunday, March 18, 2018

Huntington Ravine has MODERATE and LOW avalanche danger. Central Gully has Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern. All other areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.

 Tuckerman Ravine has MODERATE and LOW avalanche danger. Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully to identify features of concern. All other areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.

 AVALANCHE PROBLEM: Areas of visibly smooth wind slab are our primary avalanche problem today. Moderate rated terrain holds the largest and most continuous of these newly formed slabs which primarily exist in the lower half of our forecast areas. Expect these slabs to be stubborn to touchy though fairly hard, making human triggered avalanches possible and natural avalanches unlikely. The mostly wind textured snow dominant in the rest of our terrain is certainly harder still. It’s important to always remember that “Low” avalanche danger does not mean “No” avalanche danger as pockets of more reactive and softer snow can be found in Low rated terrain. Visibility should facilitate your ability to choose safer travel options, but remember that the cold temperatures and strong wind would elevate the consequences of any accident today.

 WEATHER: Wind has been the dominant factor in our snowpack development in the past 24 hours, blowing out of the W and gusting up to 122 mph on the summit yesterday before shifting NW and decreasing last night. A half inch of new snow was recorded on the summit and a trace at Hermit Lake. NW wind should continue through the day in the 40-50 mph range with a slight increase by tonight. Cold temperatures, with the mercury dipping to -14F on the summit overnight, will continue today and tonight with a summit high just above 0F. No precipitation is forecast today or tomorrow and minimal clouds should allow for good visibility. Wind and temperature should remain consistent through tomorrow night as well, with high temperatures a handful of degrees warmer tomorrow.

SNOWPACK: Gone are the widespread soft wind slabs of a few days ago, as two days of classic Mount Washington wind has hammered our upper snowpack. Expect a high degree of spatial variability in surface snow, from hard and wind textured sastrugi to areas of recently formed and somewhat softer wind slab which will vary in size but could be quite thick. Areas of most concern for instability today are relatively low in our avalanche paths. Avalanche paths have significantly developed with recent storms, and we’re seeing evidence of a widespread natural avalanche cycle in both ravines which likely occurred late last week. The general feeling this morning is, “Wow, there’s a lot of snow!” Take advantage of good visibility to help you identify features of concern as you enjoy the mountains today.

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This advisory is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
• Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast. For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or Harvard Cabin.
• Posted 8:00 a.m., Sunday, March 18, 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

2018-03-18

New snow and weather data

 

You may notice a couple of changes to the web advisory today. We frequently refer to the snowplot at Hermit Lake in our advisory but will be including the raw data which is collected every morning by the caretaker at the AMC operated facility there. You need to go to the full forecast to see the data and wind chart. As resources allow, we plan to roll out more of this type of data to help you make more informed decisions when venturing into avalanche terrain. The weather data provided by our partners at the Mount Washington Observatory continues to be critical to our forecast process but more data improves our accuracy and may prove helpful to the dawn patrol skiers and climbers out there. Special thanks to the AMC caretakers for getting up early to collect the data, Chris McKnight for the wind rose and High Charts for providing a free license.

Avalanche Advisory for Saturday, March 17, 2018

Huntington Ravine has LOW avalanche danger. All forecast areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.                                                                                       

Tuckerman Ravine has MODERATE and LOW avalanche danger. Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern. All other forecast areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.

AVALANCHE PROBLEM: Our avalanche forecast today is driven by the legendary, howling winds that hammer Mount Washington. Strong winds overnight and this morning have scoured much of our terrain but have also left firm and stubborn wind slabs in their wake. These wind slabs are the primary avalanche problem today. The moderate rated terrain in the headwall area of Tuckerman Ravine harbors the largest wind slabs with pockets of wind slab elsewhere. In low rated areas these slabs will generally be on the smaller side and should be pretty easily avoidable, though it will require good micro-route finding skills. Though these firm wind slabs will be the primary avalanche problem, the main environmental challenge you’ll face today is cold temps and wind chill. You’ll need the luck o’ the Irish to avoid frost nip if you venture above treeline today.   

WEATHER: A little over an inch of new snow was recorded at the summit in the past 24 hours with 6cm recorded at Hermit Lake. Due to the strong winds, even the tree sheltered snow plot was heavily wind effected. Winds overnight raged near 90 mph for almost 7 hours with gusts in the high 90’s or 100mph for 3 hours. A peak gust out of the WNW hit 111mph. Wind direction will continue from the NW but diminish through the day to the mid 50’s mph. Temperatures will be around -5F for a high today on the summit. Another inch or snow of snow could fall mid-day and may contribute to low visibility conditions primarily caused by summit fog. Goggles, face protection and a good whiteout navigation plan will be key today.

SNOWPACK: The 30” of snow which fell primarily on Tuesday through Thursday is wind effected to say the least. Stiff wind slabs exist even below treeline. The nor’easter responsible for the snowfall lingered and continued to drop snow in the region. As winds finally wrapped around to the west while the low exited the area, available snow on the ground was blown into our east facing terrain, resulting in wide spread natural avalanche activity. Improved visibility and reduced avalanche danger will allow further observations later today, but we can report on a few natural avalanches. Hillman’s Highway and the Main Gully in Gulf of Slides ran full extent (R5 D3) of the path and into mature forest. Hillman’s “jumped the bank” near the approach trail and ran into the woods. Duchess also avalanched as did Gully 2 in Gulf of Slides and ran close to full path (R4 D2). We’re confident that other slide paths ran but thick summit fog is lingering this morning. The ice crust that has haunted us for weeks now is on the list of snowpack features to look for today. We’ll be checking it out for extent of exposure as well as faceting nearby.

The Sherburne Ski Trail benefited greatly from this week’s snowfall. Great coverage exists, though a bit of scouring may have exposed a rock or two in the usual wind hammered sections. 

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 8:00 a.m., Saturday, March 17, 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

2018-03-17

Avalanche Advisory for Friday, March 16, 2018

Huntington Ravine has MODERATE and LOW avalanche danger. Central, Pinnacle, Odell, South, and Escape Hatch have Moderate avalanche danger. Heightened avalanche conditions on specific terrain features; identify features of concern. North, Damnation, and Yale have Low avalanche danger. Watch for unstable snow on isolated terrain features.

Tuckerman Ravine has CONSIDRABLE, MODERATE, and LOW avalanche danger. Sluice, Lip, Center Bowl, and Chute have Considerable avalanche danger. Dangerous avalanche conditions exist. Lobster Claw, Right Gully, Left Gully, Hillman’s Highway, and the Lower Snowfields have Moderate avalanche danger. Heightened avalanche conditions on specific terrain features. The Little Headwall has Low avalanche danger.

AVALANCHE PROBLEM: Strong NW wind created thick wind slabs yesterday. These will be found in greatest concentration in Considerable rated areas. While human-triggered avalanches are more likely than natural avalanches, wind slabs have the potential to run far today. A mix of cross-loading and scouring has taken place on other slopes. Pay close attention to this interplay as it may be easiest to trigger this wind slab on its outer edges. The boundary of wind slab and old surface may be blurry due to newer snow over the old ice crust. Slopes with a Moderate rating today, particularly Central Gully in Huntington, should not be taken lightly. Areas of more reactive snow will likely be found in the most sheltered areas and should be negotiated appropriately. Old icy surface or older firm wind slabs may be found in areas and will make great climbing, but also provide the potential for sliding falls. An ice axe and crampons will be useful in steep terrain today.

WEATHER: The snowy mid-March we are experiencing continued yesterday as the Summit recorded 7.3” of snow yesterday with a water equivalent of 0.75”. The arrival of this snowfall was split, early in the morning and then another dose after dark with snow flurries and blowing snow all day. Wind stayed W and WNW for the day with speeds in the 60-80mph range with a peak gust of 98mph. Unsettled weather will linger over the region today, keeping the summits in the fog with intermittent upslope snow showers bringing up to 2” of snow. Winds will remain NW 50-70mph to start the day and increasing in the afternoon with gusts topping 100mph after dark as a cold front moves over NH. The current temperature on the Summit is 1F and should drop through the day to the negative-teens F tonight.

SNOWPACK: The Mount Washington Observatory recorded 27” of snow (2.57” SWE) over the past 72 hours that was finally subjected to classic strong NW wind. A combination of scouring and loading has taken place. The heaviest loading is on slopes in the direct lee of NW wind, particularly at mid-elevations and under terrain features. This magnitude of wind (sustained 60-80mph) will have created firm, stubborn wind slab as well as a combination of scouring and cross-loading on slopes with a southern or northern exposure. This wind slab in places now sits on previous layers of wind slab that formed over the past two weeks. It is likely that the tensile strength of yesterday’s slab will bridge over weak layers that may linger on deeper interfaces, but an avalanche stepping down into these other weak layers is possible.

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 8:25 a.m., Friday, March 16, 2018. 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

2018-03-16

WMAEF Continuing Education Series

Join us this Saturday, March 17, at 5pm at International Mountain Equipment (IME) for the third installment in the White Mountain Avalanche Education Fund’s Continuing Education Series. Helon Hoffer will be reviewing fracture mechanics and exploring fracture arrest. We’ll be looking at the big wind slab avalanche that occurred on February 8 throughout the talk and discussing why the slab boundary stopped where it did. While this talk may raise more questions than answers, it will help give a better understanding of why dry slab release occurs the way it does.

Avalanche Advisory for Thursday, March 15, 2018

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger. Yale, Central, Pinnacle, Odell, South and Escape Hatch have Considerable avalanche danger. Dangerous avalanche conditions exist. North and Damnation Gullies have Moderate avalanche danger. Evaluate snow and terrain carefully to identify features of concern. 

Tuckerman Ravine has CONSIDERABLE avalanche danger. All forecast areas have Considerable avalanche danger. Dangerous avalanche conditions exist. Lower Snowfields is still lacking snow cover though Moderate danger exists due to the Duchess runout. The Little Headwall has Low avalanche danger with pockets of unstable snow, ice and holes in the snowpack.

AVALANCHE PROBLEM: An increase in wind speed and a shift in wind direction will keep avalanche danger elevated today. Recent snowfall will be carried by NW winds and build wind slabs in many areas. Natural wind slab avalanches are possible in bigger terrain such as the Lip, Center Bowl, Chute and Hillman’s Highway in Tuckerman Ravine and Central Gully in Huntington. Dry loose avalanches are likely in the steepest areas of both Ravines and will contribute to the likelihood of human triggered avalanches on the approach to steep pitches of ice or rock. Wind slabs should become firm and stubborn with anticipated wind speeds but not before becoming unstable as they build. Staying on low angle terrain, avoiding runouts and traveling one at a time while making careful snowpack assessments will be critical today if you choose to venture into avalanche terrain. Precious little of this low angle terrain exists in our forecast zones, so seeking out lower elevation, less wind effected terrain may be your best bet until wind subsides and visibility improves.  

WEATHER: Light to moderate upslope snow showers are continuing this morning and may bring 2-4” more snow today. Almost 2” of snow water equivalent fell in the past 2 days bringing 20” of snow to the summit. Snowfall reports from the area were highly variable with this storm due to banding and intense squalls. This brings some uncertainty to our assumptions about how much snow is available for wind transport in the alpine. Though no snowfall totals are available from the west side, it is pretty clear that there is enough snow on the ground to create avalanche problems. Anticipate WNW wind to continue where it sits in the low 60 mph range and blow in the 50-70 mph range with gusts to 90 mph. Fog and blowing snow will reduce visibility and contrast and challenge visibility. 

SNOWPACK: An old adage which holds a lot of truth says that avalanche danger in a maritime snowpack is quick to rise and quick to fall. Warm temps and lots of snow normally lead to rapid settlement and bonding of grains in that snow climate. While our region and certainly the weather pattern that we’ve had lately are generally maritime, the major player in our forecast areas that defies that conventional wisdom is the action of the wind. You likely saw speedy settlement of the copious amounts of snow at lower elevations yesterday and likely much of the 8% density snow that fell at 3800’ yesterday settled some as well. But count on the polar part of our polar maritime snowpack to kick into gear with colder temperatures slowing settlement and high winds building thick and stubborn wind slabs. Recent human-triggered avalanche activity here as well as in Vermont is a reminder that our snow and weather is dynamic in our limited avalanche terrain. Don’t let the overall scarcity of new snow this winter blind you to red flags such as rapid snowfall or wind loading that signal danger. There is good skiing and riding to be had on the John Sherburne Ski Trail.

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 8:05 a.m., Thursday, March 15, 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

2018-03-15