Avalanche Advisory for Wednesday, March 22, 2017

This advisory expires at Midnight.

Huntington and Tuckerman Ravine have CONSIDERABLE and MODERATE avalanche danger. In Tuckerman, Sluice, Lip, Center Bowl, and Chute have Considerable avalanche danger. Central, Pinnacle, and Odell Gullies in Huntington Ravine have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Dangerous avalanche conditions exist. Careful snowpack evaluation, cautious route-finding, and conservative decision-making are essential. All other forecast areas of both Ravines have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully. The only exception to these ratings is the Little Headwall, which has Low avalanche danger. Natural and human triggered avalanches are unlikely.

AVALANCHE PROBLEM: Wind Slab formed overnight is the primary avalanche problem today. With a currently upside-down, firm over soft nature, this surface layer will be particularly sensitive to a trigger this morning. A lack of visibility hampered morning observations, but we expect this slab to be thick in places and widespread over Chute, Center Bowl, Lip, and Sluice in Tuckerman as well as Central and lower Pinnacle and Odell gullies in Huntington. Pockets in lee areas of west through northwest winds will hold this wind slab in Moderate rated areas. Increasing wind speeds throughout the day will cause this instability to peak this morning or mid-day, decreasing as we approach wind speeds that should scour Huntington and create pockets of very firm slab in Tuckerman

WEATHER: It’s cold and windy up here. The summit is currently recording -2 F, with sustained northwest wind nearing 60 mph and gusts to 70. Throughout the day, this wind will increase, nearing 100 mph, and temperatures dropping to -20F. Snowfall and cloud cover is tapering off as this wind increases and temperature drops, remaining partly cloudy with no precipitation this afternoon.

SNOWPACK: We’re seeing a significant amount of new and blowing snow on the mountain, with 3.5 inches of snowfall recorded at Hermit Lake and 5 inches at the summit in the past 24 hours. Underneath this new snow, a mix of relatively stable surfaces exist. This ranges from pencil to 1 finger hardness wind slab over much of the terrain as well as areas of previously scoured old rain crust. The melt-freeze cycles over the past few days, with current temperatures well below freezing, have facilitated bonding between this wind slab and underlying layers. Snow that fell yesterday and last night arrived on West winds in the mid-40 mph range that shifted this morning to the Northwest and increased, with gusts to 70 mph. This transport of new snow from our largest fetch zones for Tuckerman Ravine has likely deposited a significant amount of snow in the Chute, Center Bowl, Lip, and Sluice. In Huntington, Central Gully should hold the largest wind deposits, both above and below the choke point, with Pinnacle and Odell having quite a bit of similarly deposited snow below the ice.  The wind slab formed in the aforementioned areas will display increasingly upside-down characteristics, with softer deposits made by the light to moderate overnight winds sitting underneath the more dense snow loading under the current winds.  Accordingly, the growing wind slab will be increasingly sensitive to a trigger.  Winds are forecast to increase through the day, with peak summit gusts around 100 mph late today, so we’re likely to see a morning or mid-day peak in instability as this high wind begins to erode the newly formed surface slabs, decreasing their size and sensitivity to a trigger.  Sensitive wind slabs could remain, though, in lower and more sheltered pockets of our considerable rated 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 the Harvard Cabin.

Posted 9:20 a.m., Wednesday, March 22, 2017. 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

2017-03-22

Avalanche Advisory for Tuesday, March 21, 2017

This advisory expires at Midnight.

 

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

AVALANCHE PROBLEM: This morning, areas of hard wind slab will be encountered on north facing aspects. East and south facing slopes received sun and warmth yesterday that refroze last night and should present more of a long sliding fall hazard than avalanche problem this morning. Snow showers through the day may bring up to 2” of new snow with increasing W and NW wind. Pockets of wind slab will develop, particularly in sheltered areas of westerly wind, creating and increasing avalanche hazard as the day progresses. These pockets will likely be isolated due to the small amount of incoming snow and soft due to lighter wind speeds.

WEATHER: Light wind, warm temperatures, and clear skies allowed the surface snow of east and south aspects to warm yesterday. Clouds developed overnight and should continue to thicken as the day progresses. As the cold front approaches, temperatures may spike for a brief period this morning before sharply dropping in the afternoon when the front arrives. The cold front contains some moisture which should create scattered upslope snow showers during the day with possibly up to 2” by tonight and another 2” by tomorrow morning, however, it seems likely this total will be on the lower side. Current wind on the Summit is NW at 21mph. This will shift to the W through the day and increase to 40-55mph by nightfall.

SNOWPACK: Wind slab on top of the old melt-freeze surface has now gone through multiple periods of warming, the most significant being yesterday. The warming on Saturday and Sunday was minimal and not enough to affect the stability of this slab. Yesterday, east and south facing aspects received a prolonged period of warmth. In places where the wind slab is thin, this warming likely penetrated through the slab and into the snowpack beneath. Overnight, the freeze will have created a strong bond between these two layers. In places where the slab was thicker, such as the Lip and Center Bowl, the warming weakened the tensile strength of the slab for a period yesterday afternoon but did not penetrate far enough for the freeze to improve the bond to the old surface. The cold last night will have frozen the moistened surface snow of these thick areas into a more cohesive slab, improving the overall strength of the snowpack. Areas that did not receive warming yesterday (north facing aspects) contained firm, wind-textured snow or large areas of older surface that will be largely unchanged today. New snow arriving today will be subjected to increasing wind from the west. If traveling in avalanche terrain late in the day today, be prepared to encounter isolated pockets of new wind slab in lee areas of west wind or tucked under terrain features.

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, March 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

2017-03-21

Avalanche Advisory for Monday, March 20, 2017

This advisory expires at Midnight.

Huntington Ravine will have MODERATE and LOW avalanche danger. Damnation, Yale and Central Gully will have Moderate avalanche danger. Natural avalanches are unlikely but human-triggered avalanches will be possible this afternoon. All other forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

Tuckerman Ravine will have MODERATE and LOW avalanche danger. Sluice, Lip, and Center Bowl will have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches will be possible this afternoon. All other forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely.

 AVALANCHE PROBLEM: Our primary avalanche problem today will be caused by the breakdown of strength in existing wind slabs due to heating of the snow. These firm slabs have been strong enough to bridge over soft weak layers beneath and resist failure but today’s heating will be the first real test since their formation. Today’s ratings are based on slope aspect as well as the size and continuity of the slabs. Lobster Claw and Right Gully along with North Gully in Huntington have much less snow in them or have already seen heating during yesterday’s mid-day warmth. As a result, those slopes are less likely to avalanche due to a human-trigger than nearby slopes with a moderate rating. When you begin to sink in to your boot tops or when it becomes easy to make a snowball on a steep slope, it will be time to reevaluate whether you should be travelling in that terrain.

 WEATHER: It has been a cold and snowy March so far, though today’s forecast is definitely spring-like. So far this month, temperatures are averaging 10F below normal and we are just 2” of snow shy of the monthly average with 11 days remaining in the month. Current temperature at Pinkham Notch is 10F, with 23.5F at Hermit Lake elevation on the Auto Road and 17F on the summit. With the warm band in place at Ravine elevations and relatively light NW winds, we are on track to begin the snow destabilizing warm up. Summit high temperature are forecast to reach the mid-20sF with NW winds in the 20-35mph range. Wind speeds this low from that direction are generally not enough cool our slopes. This is especially true in wind sheltered areas in the Ravine which receive a fraction of the wind that the summit feels.

SNOWPACK: Our snowpack now consists primarily of one-finger to pencil hard wind slab with softer pockets on the surface in southeast facing aspects. The wind slab has weak interfaces in the upper layers along with soft layers below. Last week, the upper slabs which range in thickness from a few centimeters to a meter, demonstrated the potential to propagate a crack, as seen in this video, but resisted doing so from human-triggers due to their strength. Today’s warming may change this. Though heating today doesn’t seem to indicate fast enough melting to lubricate the ice crust, it does raise concerns for weakening the upper slabs enough to make them prone to cracking, especially at a thin spot near the edge of a slab or over a rock. Air temperatures today may reach the point where even shadier aspect warm and soften a bit so more heavily scoured features like Left Gully and Hillman’s may soften. The weather conditions affecting our snowpack today will be as dynamic as those that created it, so look for clues and anticipate softening and weakening of the wind slabs as well as refreezing of the snow as it cools down again as the sun moves across the sky.

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, March 20, 2017. A new advisory will be issued tomorrow.

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

2017-03-20

 

Avalanche Advisory for Sunday, March 19, 2017

This advisory expires at Midnight.

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

AVALANCHE PROBLEMWind slab remains our avalanche problem today. Primarily formed Wednesday night and Thursday, this firm slab exists over much of our terrain, is largest in Sluice, Lip, and Center Bowl, and can be found in pockets of varying size on most aspects. Bonds between this layer and the underlying snow surface have gained strength over the past several days. While resistant to a human trigger, the resulting avalanche could be large. This possibility, albeit unlikely, certainly remains and demands respect in your travel decisions. Where this slab is not present, an old, icy rain crust is the snow surface. It’s darker in appearance and quite hard underfoot making it fairly easy to differentiate from the areas of wind slab. Offering a stable surface to travel on, this crust is certainly hard and also provides good crampon purchase, limited edging ability on skis or snowboard, and a great surface on which to take a long sliding fall.

WEATHER: Yesterday, clear skies, mild temperatures, and low winds allowed many to enjoy a great day of recreating on the mountain. Today will be similar, although it is likely clouds will be more present and may even create occasional snow showers in the afternoon. Winds will start from the SE at 5-20mph and increase in the afternoon to 25-40mph while shifting to the N by the end of today. Currently, the temperature on the Summit is 8F, with highs for the day reaching the mid-teens.

SNOWPACK: After the Tuesday Nor’easter cleared, much of our terrain was left scoured to old surface due to strong E winds. The seven inches (7”) that arrived Wednesday and Thursday came on W winds and has since been treated to strong winds from the NW. The result of this 7” is more of the surface snow being wind slab than old surface. The south wall of Huntington (Odell, South, and Escape Hatch) as well as The Chute, Left Gully, and Hillman’s in Tuckerman have wind slab that is firm (pencil hard) and very wind textured. Some of the higher ends of these gullies are scoured to the old surface, but just the very tops. Gullies with an east-aspect, Central, Sluice, Lip, and Center Bowl, contain the most contiguous and thickest wind slab. This will be firm (pencil to one-finger hard), but slightly less dense than the southern gullies. The upper layer is supportive and providing bridging strength to potential weaknesses beneath, but caution should be exercised when entering or leaving these areas as the edge of the slab will be the thinnest and the area where there is potential to affect the weak layer. Thin spots will also be found around terrain features like cliffs and rocks hidden beneath the snow surface. These areas are modeling the classic example of low probability but high consequence. It is unlikely they will avalanche, but if they do it would be a hard slab that would likely entrain a good amount of snow. The north wall of both ravines contain some of the softest wind slab. The upper reaches of Damnation yesterday had wall-to-wall four-finger (4F) hard snow on top of a fist (F) hard layer. This slab was 50cm deep and was still small enough to considered a pocket, but worth keeping an eye on. Bluebird skies yesterday along with no winds allowed some of the old rain crust surface to soften where exposed. This was not widespread and limited to areas that received the maximum amount of sun possible. With intermittent cloud cover today, we are less likely to see the corn cycle continue.

 

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 7:40 a.m., Sunday, March 19, 2017. A new advisory will be issued tomorrow.

Ryan Matz/Helon Hoffer, Snow Rangers
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2017-03-19

Stranded climbers

At around 11:30a.m., a pair of hikers set out from Pinkham Notch to summit via Huntington Ravine. At approximately 4:45p.m., snow ranger staff were contacted by AMC front desk staff that there were 2 hikers stranded near Central Gully in Huntington Ravine. Scouting in the Ravine revealed that the pair of climbers were actually located approximately 500′ below the top of the rim of Huntington between Damnation Buttress (5.6 WI3- M2-3; 700′) and Damnation Gully (WI3, 1,000′).  Two snow rangers climbed to the pair while one spotted from below. Two snow rangers and a Mount Washington Volunteer ski patroller approached the top via snow tractor on the Auto Road while 2 more ski patrollers served in dispatch and radio communications roles. The pair was reached at approximately 7pm by the climbing team and led to the top with assistance from the other two snow rangers from above. Rescuers and the pair reached the waiting Mount Washington Observatory snowcat at 10:02pm and returned to Pinkham Notch by midnight.

Analysis: The party reported that they had inquired at the AMC Front Desk about whether they could make it through Huntington Ravine to the summit without ropes and indicated that they were told that they could. The pair had limited climbing experience but managed to climb through 4th and low 5th class terrain unroped, with crampons and walking axes but without harnesses or other technical gear. Regardless of the source of the miscommunication with the front desk staff, it is important to thoroughly research an intended route, to re-evaluate plans based on time of day, climbing difficulty, along with prevailing weather conditions and experience level of the party. Fortunately, the pair were properly equipped with enough clothing, food and fluids. Though the summit temperature was around 10F that evening, relatively calm SE winds in 20 mph range made for a merely uncomfortable wait rather than a more serious outcome. It is interesting to note that a party of three found themselves stranded in the same position in similar conditions several years ago. It seems that the same line-of-least-resistance appears attractive to summit bound hikers confronted with the illusion that the Huntington Ravine trail or Central Gully are more difficult. While both of those routes are comparable in difficulty and have equally serious consequences in the event of a fall, the hardest climbing appears near the start of those two routes where a hiker could receive more immediate feedback on their route selection.

Avalanche Advisory for Saturday, March 18, 2017

This advisory expires at Midnight.

Huntington Ravine has LOW avalanche danger. Natural and human-triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

Tuckerman Ravine has MODERATE and LOW avalanche danger. Sluice, Lip, and Center Bowl have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. All other forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely.

AVALANCHE PROBLEM: Our primary avalanche problem today is wind slab; widespread across Moderate rated areas and in pockets of low rated areas.  Following our Tuesday Nor’easter, and subsequent snow showers Wednesday night, strong (70+ mph) west to northwest winds deposited and packed firm snow on lee terrain.  Existing across Sluice, Lip, and much of Center Bowl in Tuckerman Ravine, this slab, that is thick in places, will likely be stubborn to trigger, providing a low probability, high consequence avalanche problem.  In Huntington, Central Gully is showing the most wind deposited snow, particularly below the choke point.  Other forecast areas have been scoured to an icy crust that is several weeks old, but also hold pockets of this new wind slab that should be easy enough to identify and avoid.

WEATHER: Temperatures rose overnight on the summit while valley locations cooled considerably as cold air settled to lower elevations. Currently, the temperature on the summit is 5F with 1F at Pinkham Notch. High pressure overhead has allowed wind to calm at Pinkham Notch with 21mph from NNW on the summit. Expect clear skies and variable winds later with a high near 15F on the summit, warmer in the Ravines. There has been no new snow recorded on the summit since late Thursday night.

SNOWPACK: It’s still winter up here! The recent Nor’easter, followed by a significant wind event, has maintained a dynamic snowpack in the ravines. A strong and supportable rain crust formed several weeks ago is present in the snowpack in essentially all of our terrain.  Moderate winds from nearly every direction during and after the Nor’easter created a layering of varied density wind slabs, much of which were subsequently wiped out by stronger West to Northwest winds Wednesday night and Thursday. Areas lee of these winds, particularly Center Bowl, Lip, and Sluice, hold a firm, pencil to one finger hardness wind slab of varied thickness from an inch to several feet.  Other areas hold pockets of a similarly deposited snow. These slabs will be stubborn to trigger and offer fairly good conditions for travel, still demanding cautious travel practices. The old rain crust is the primary surface where this recently deposited snow does not exist. This crust is quite stable but is smooth and icy and would easily allow a long sliding fall. The new and old surfaces can be distinguished by color: the old crust is significantly darker than the recently deposited snow. As spring arrives and the sun heats the snow in sheltered, south facing areas near trees and rocks, be on the lookout for a some reduction in strength of existing slabs as heat weakens bonds between grains.

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

Posted 8:00 a.m., Friday, March 18, 2017. A new advisory will be issued tomorrow.

Ryan Matz/Frank Carus, Snow Rangers
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2017-03-18

Avalanche Advisory for Friday, March 17, 2017

This advisory expires at Midnight.

Huntington Ravine has MODERATE and LOW avalanche danger. Central Gully has Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. All other forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely.

Tuckerman Ravine has MODERATE and LOW avalanche danger. Sluice, Lip, Center Bowl, Chute, Left and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. All other forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely.

 AVALANCHE PROBLEM: Densely packed, wind transported snow has built wind slab over a softer layer of loose snow over the past 48 hours. Due to the potential size of these slabs and the challenges posed by avoiding them, they are the primary avalanche problem in moderate rated areas today. While these slabs may propagate a crack, the strength of the firm slab above makes these slabs very stubborn. This type of wind slab is most concentrated in areas in the lee of a northwest wind such as just beneath the ice in Center Bowl, below the rollover in the Lip and high in Chute. Central Gully appears to have an area of this firm slab, as well. In addition to the primary firm, wind slab problem, softer pockets of wind slab exist here and there in both Ravines but are much smaller and discontinuous so shouldn’t pose too much of a challenge to avoid. Hillman’s and Left Gully are on the low end of the moderate rating due to more areas being scoured. Evaluate snow and terrain carefully today.

WEATHER: Around 2.5” of new snow fell on the summit in the past 24 hours on strong west and west-northwest winds. Winds remain strong from this direction after blowing in the 60-75 mph range during most of the past 24 hours. No new snow is in the forecast today and summit fog is slowly clearing now. Expect mostly sunny skies and cold temperatures, currently -8F, rising to just above 5F today with moderating wind from the NW in the 30-45 mph range.

SNOWPACK: More field time yesterday revealed the wind-scouring action of recent high wind speeds. Most of the softer and more sensitive wind slabs that remained after the passage of the last nor’easter were either ripped up and blown away or bridged over by firm, pencil hardness new wind slabs. Pockets of smooth wind slabs exist in some areas and while there is a softer layer beneath, the bridging power of the overlying firm slab allowed us safe passage yesterday on the slope between Lobster Claw and Right. Of equal or even greater concern than the areas of stubborn wind slab in the terrain is the widespread ice crust that is exposed after the hammering winds over the past weeks. The old adage that the “leader must not fall” is applicable on this surface since you would be fooling yourself to think that self-arrest is possible on this surface in steep terrain. Careful route-finding, roping up and/or not falling are key on our above this surface. A race tune on your backcountry skis could also be helpful.

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., Friday, March 17, 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

2017-03-17

 

Avalanche Advisory for Thursday, March 16, 2017

This advisory expires at Midnight.

Huntington Ravine and Tuckerman Ravine have CONSIDERABLE avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Dangerous avalanche conditions exist. The only exception to this rating is Little Headwall which has Low avalanche danger. A combination of small wind slabs, ice bulges and open water exist there.

AVALANCHE PROBLEM: There is Considerable danger from new wind slabs that developed overnight and that will grow in size today. These wind slabs will be found in lee areas of west and northwest winds. Sluice, beneath the ice in Lip and Center Bowl, in Chute, as well as high in Left Gully and Hillman’s will see the greatest likelihood of a natural avalanche and the greatest sensitivity to a human trigger. It would be challenging to travel through these areas without triggering a wind slab. Similar conditions are likely to be found in Huntington Gullies that have an easterly aspect. Northern gullies in Huntington and Lobster Claw and Right Gully in Tuckerman Ravine have larger but likely more stubborn wind slabs lingering from the strong north east winds associated with the most recent nor’easter. These areas including, North, Damnation, and Yale, will also have some cross-loading of new snow which will complicate assessment and travel.

WEATHER: Lingering moisture from the exiting nor’easter will create fog and generate light snow showers at higher elevations today. The trace-2”, combined with 22-26” of recent snow on the ground, will give west and then northwest winds something to work with. Wind is currently blowing from the west in the mid-40’s mph with gusts to the mid-50’s. The past 12-14 hours have seen roughly these same wind speeds from the west with a 3-4 hour period early this morning of NW wind in the 60’s gusting to the 70’s mph. Peak wind loading of our forecast areas likely occurred during that time period but wind, continued blowing snow, and fog will continue to make conditions a bit rowdy. Wind transported snow is the critical factor affecting snow stability today.

 SNOWPACK: Wind driven snow will stress weak layers in wind slabs deposited during the recent big storm. Due to strong easterly and northeasterly wind, those slabs were limited to south facing aspects that were downwind of a sizable fetch. This means these slabs were primarily in Lobster Claw, Right Gully, low in the Bowl and on the approaches to climbs on the right side of Huntington. Yesterday, old, gray ice crust and sastrugi was visible in most of Center Bowl, Left Gully and Hillmans though certainly larger pockets of wind slab were mixed in. The alpine zone was heavily scoured as well, though plenty of snow likely remains in large drifts. It is important to remember that travel and assessment will be challenging due to fog, blowing snow and cold conditions. Today might be a good day to climb and ski at lower elevations and let the wind slabs sort themselves out in the higher and steeper terrain.

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

Posted 8:30 a.m., Thursday, March 16, 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

2017-03-16

 

 

Avalanche Advisory for Wednesday, March 15, 2017

This advisory expires at Midnight.

 

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

Tuckerman Ravine has CONSIDERABLE avalanche danger. All forecast areas have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Dangerous avalanche conditions exist. Careful snowpack evaluation, cautious route-finding, and conservative decision-making are essential. The exception to this is the Little Headwall which has Low avalanche danger. Watch for unstable snow on isolated terrain features.

AVALANCHE PROBLEM: Wind Slab developed in all avalanche terrain yesterday and last night. As winds were strong and blew from many directions, the wind slab does not appear to be thick, but exists on most aspects and can be found primarily in the bottom and mid-elevations of forecast areas. As the wind increases this afternoon, avalanche danger will increase and may push the upper end of the current rating by midnight. The danger will also increase when the forecast 2-4” of snow arrives. If the total is closer to 4”, we could exceed our current ratings on lee slopes of west and northwest winds.

WEATHER: Yesterday’s nor’easter delivered 19.2” of snow with a liquid equivalent (SWE) of 1.5”. Winds blew strong during the course of this storm, starting from the SE and moving to the E during the heaviest snowfall periods with steady speeds of 100mph. At midnight, the wind continued its counter-clockwise rotation through the NE and speeds dropped sharply to 15mph. It was around this time that the snow stopped as well. Since midnight, winds moved to the W and are currently 27mph. Today, winds will shift between the W and NW, slowly increasing as the day progresses. Wind speed should top 50mph by late afternoon. Skies are clear this morning, but with moisture still lingering to the west that should move in this morning, summits will return to intermittent fog and occasional snow showers, bringing 2-4” through the day. Tonight, as winds move to the NW and increase to 60-80mph, another 1-3” of snow may arrive.

SNOWPACK: Wind slab from various storms over the past week sits on top of a solidly frozen snowpack. Prior to yesterday, the largest pockets of wind slab resided in the Lip and Center Bowl area of Tuckerman. Snow that fell yesterday was subjected to strong winds from multiple directions for much of the day. This resulted in slopes loading from all directions. The wind slab that formed yesterday will likely have many layers and minute density changes within, creating many interfaces to possibly fail on. Due to cross-loading, north and east-facing slopes contain connected wind slab for much of the forecast area. South-facing slopes were scoured by winds at the top, but contain areas of wind slab in the bottom of these forecast areas. Signs of avalanche activity yesterday can be found, although it appears most fractures were on the smaller side and have since reloaded. As snow starts today and winds increase from the W and NW, significant loading will take place on east-facing slopes. With most of yesterday’s snow still clinging to slopes, avalanche activity tonight may be on the larger side.

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

Posted 8:40 a.m., Wednesday, March 15, 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

2017-03-15

Avalanche Advisory for Tuesday, March 14, 2017

This advisory expires at Midnight.

Huntington and Tuckerman Ravine have CONSIDERABLE avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Dangerous avalanche conditions exist. Careful snowpack evaluation, cautious route-finding, and conservative decision-making are essential.

AVALANCHE PROBLEM: The incoming Nor’easter will create Wind Slab in avalanche terrain. Wind direction will dictate where this problem forms and to what degree loading happens with increasing hazard through the day. Light south winds this morning will load north-facing slopes during the morning. As the wind shifts to the east and increases in speed, north-facing as well as south-facing slopes will see cross-loading. While our forecast areas do not include slopes with a western aspect, west-facing slopes outside of our forecast area will see significant wind loading as the wind shifts to the east. As the wind direction continues its move toward the north, south-facing slopes will see the most loading with cross-loading finally bringing snow to east-facing slopes. As this shift to the N and NW takes place, areas in Tuckerman and Huntington Ravine may exceed the Considerable rating after this advisory expires at midnight. Much of the snow from today will move to the west side of Mount Washington. Looking ahead to later tonight and tomorrow, NW winds will bring this snow back to the east side, likely leading to multiple avalanche cycles.

WEATHER: Paying close attention to the changing weather today will be paramount for safe travel. Snow is now falling at Hermit Lake. Currently on the Summit, winds are 15mph from the S. As the morning progresses, wind speed will increase and shift to the E by early afternoon. Wind speeds will depend on how the storm tracks. At the moment, wind speeds reaching close to 100mph seems likely at some point this evening. With snowfall reaching its heaviest (2-3” per hour) in the afternoon/evening hours, wind direction will continue wrapping counter-clockwise, reaching due N around the time this advisory expires. Snowfall total will be significant with quite possibly 12” by dark and close to this same amount by morning tomorrow.

SNOWPACK: Our base snowpack went through a significant melt-freeze cycle at the end of February and is solid. Since then, we recorded about 16” of snow that has seen strong wind. Much of the terrain was scoured and wind slab that formed in the lee areas of steep terrain and behind terrain features is firm and proven unreactive to human triggers. The weak layer that exists under this wind slab will be tested by avalanche cycles over the next 36 hours. Stepping down into this layer is a possibility overnight and into tomorrow. Incoming snow and the shifting wind today will be the real factor affecting decision-making. Expect limited visibility due to blowing snow, requiring meticulous navigation with a constant eye on the changing wind.

 

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

Posted 8:30 a.m., Tuesday, March 14, 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

2017-03-14