Avalanche Advisory for Friday, March 31, 2017

This advisory expires at Midnight.

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

AVALANCHE PROBLEM: Overnight, a solid freeze of wind loaded slopes, which had softened in the sun yesterday, has reduced our stability concerns to snow arriving this afternoon. A low pressure system passing to the south will bring up to an inch of water to the area with the majority of this falling tonight and tomorrow. Low wind speeds from the southeast and 2” of snow will keep avalanche danger low today with natural and human-triggered avalanches unlikely in all areas. Avalanche danger will continue to rise through the weekend so anticipate elevated danger through Sunday, when winds from the northwest load snow into our forecast area.

WEATHER: Daytime temperatures yesterday reached 19F on the summit but low wind speeds and plenty of sun warmed things up quite a bit in our forecast areas. A southwest flow overnight has allowed temperatures to climb a bit more. Expect summit temperatures to reach into the low 20’sF today with continued light winds which will slowly shift counterclockwise from the current westerly position to the southeast by nightfall. Wind velocity is forecast to remain very light, reaching only the low 20’s mph this afternoon with the pitot registering 5.2 mph at this writing. Snow will begin this afternoon with a half inch falling by nightfall according to adjusted NWS models, though Observatory forecasts seem to indicate a trace-2”. In either case, low snowfall amounts and light wind speeds are key factors in avalanche danger today.

SNOWPACK: The rain soaked or otherwise settled deeper snowpack creates no stability concerns in our terrain now. The 2” of snow that fell through Wednesday night created some nice skiing and riding for folks yesterday with generally stable snow loaded into lee areas of a west wind. Solar aspects heated the new snow and created mashed potatoes by early afternoon, despite the summit temperature which reached only 18F by nightfall with wind speeds in the 10-15mph range. This snow is now refrozen and should allow for good bonding with the new snow which will most likely contain a weak layer due to increasing winds, increasingly dense snow or both. The hard snow and old icy bed surface will make long sliding falls possible in the terrain today with crampons and ice axes key equipment in steep 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 8:14 a.m., Friday, March 31, 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

2017-03-31

Avalanche Advisory for Thursday, March 30, 2017

Huntington Ravine and Tuckerman Ravine have LOW avalanche danger. Natural and human-triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.
AVALANCHE PROBLEM: The wind slab avalanche problem today will present less hazard management problems than the hard, icy refrozen rain crust beneath. Rain on Monday and Tuesday followed by nearly 24 hours of summit temperatures near 40F were accompanied by snow eating fog. Temperatures dropped to single digits yesterday and last night as snow showers deposited around 2” of new snow in our forecast areas. These cold temperatures combined with the scant amount of new snow on N and NW winds in 50-60 mph range created a nasty dust on crust. The bed surface is rock hard and icy with plentiful options for skirting any pockets of new and potentially unstable wind slab. Small avalanches could be triggered on isolated areas today.
WEATHER: High temperatures on the summit forecast to reach the mid-teen’s F and diminishing winds will make for a fine but wintry feeling day. Plenty of sunshine and good visibility accompany the passage of a high pressure ridge but don’t expect enough warming to soften snow surfaces much, if at all. The current temperature at Hermit Lake is 19F with light wind, summit is 8F with a northwest wind at 40 mph. The big news on the weather horizon is the approaching snow storm that appears to be on track to bring up to a foot of snow to the summit overnight Friday and into Saturday. Be sure to check the avalanche advisory and weather forecast before committing to a trip in the mountains this weekend. Fresh snow followed by nice weather on a weekend is a classic setup for humans having run-ins with avalanches.
SNOWPACK: Rain and warm temperatures have reduced stability concerns for today, as well as for tomorrow’s storm, to new snow and new wind slabs. Widespread icy surface exists through the terrain and is easily visible by its darker gray color. Microspikes on lower angled terrain are the order of the day, along with crampons and ice axe accompanying a strong motivation to not fall on steeper slopes. The Sherburne Ski Trail is an icy junk show and the Little Headwall has running water again, though should be passable after tomorrow’s snow. All in all, the rain and warm weather early this week set us up again for a corn cycle that will be put on hold for a while longer. The next weather system will refresh our already copious amount of snow and bring with it stability concerns for the first weekend in April.

 

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., Thursday, March 30, 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

2017-03-30

 

Avalanche Advisory for Wednesday, March 29, 2017

This advisory expires at Midnight.

All forecast areas of Huntington and Tuckerman Ravine have LOW avalanche danger. Natural and human-triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features. Generally safe avalanche conditions exist

AVALANCHE PROBLEM: Current weather has removed the threat of wet avalanches. Saturated snow from warm and freezing rain will be subjected to cold temperatures today and turn to an impenetrable snowpack. This will create a slick sliding surface that will necessitate the use of crampons and an ice axe for safe travel. With up to 2” of snow possible this afternoon on rapidly increasing NW winds, wind slab may develop in areas. This will likely be isolated behind terrain features due to strong wind and a hard snow surface.

WEATHER: Between Sunday evening and Tuesday night, the Summit recorded 0.51” of water as various forms of mixed precipitation. This same period also saw a maximum temperature of 36F and a minimum of 23F, with only a three-hour window below 28F. Early this morning, cooling began with a current temperature of 18F on the Summit and 22F at Hermit Lake. By tonight, the thermometer will likely be in the single digits in areas. Winds will remain from the NW and increase through the day, possibly breaking the century mark. Snow showers may develop in the afternoon, bringing up to 2” today and another 1” tonight.

SNOWPACK: After a two days of warmth, colder conditions are returning to the mountains. Just over half an inch of water fell in various forms of mixed precipitation on Monday and Tuesday. Combined with the above freezing temperatures, all surfaces became saturated. As the cold freezes this wet snow, the snowpack will lock up. High wind speeds will help drive the freezing process, but in areas that have not seen much recent traffic or have vegetation hidden just under the surface, expect postholing to be an issue for the early part of the day. Areas that have more exposed old surface will freeze quicker and will be prime surfaces for long, sliding falls. Snow forecast for the afternoon will be subjected to strong wind and have trouble sticking to the hard snow surface. If traveling later in the day, pockets of wind slab may develop, but these will likely be driven far down the terrain and be tucked in behind 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 Harvard Cabin.

Posted 8:20 a.m., Wednesday, March 29, 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

2017-03-29

Avalanche Advisory for Tuesday, March 28, 2017

This advisory expires at Midnight.

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger today. Central Gully has Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Dangerous avalanche conditions exist. All other forecast areas have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully to identify features of concern.

Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger today. The Sluice and Lip have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Dangerous avalanche conditions exist. All other forecast areas have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully to identify features of concern. The exception to this is the Little Headwall which has Low avalanche danger. Natural and human-triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

AVALANCHE PROBLEM: The avalanche problem today will be wet slab. The hazard will increase today slowly due to temperatures remaining only just above freezing and cloud cover remaining in place. With minimal precipitation forecast today, the hazard will lie largely in meltwater lubricating a layer within the snowpack rather than a rapid additional load. The greatest hazard for the day will be in places where the wet slab is the thickest, such as the Lip or Central Gully, as these areas have the potential to produce larger avalanches than other forecast areas. As wet slabs act as liquid concrete once they release, bear in mind that even a thin wet slab can push people into potentially hazardous terrain.

WEATHER: Precipitation ended yesterday in the early afternoon with the heaviest period of freezing rain in the early morning. All told, the Summit recorded 0.37” of water that came primarily as freezing rain and ice pellets. Current temperatures around the mountain are 28F at Pinkham Notch, 40F at Hermit Lake, and 33F on the Summit. The wind is currently 33mph from the W and should remain there for most of the day, shifting slightly toward the NW tonight. Cold air is dammed between very slow moving systems this morning which will cause clouds and summits fog to linger. A cold front is approaching and should arrive this evening. The highest chance of rain is associated with this front tonight, bringing up to 0.1” of water, possibly mixing snow flurries later tonight.

SNOWPACK:  Our terrain has seen above freezing temperatures since yesterday early afternoon, but as these temps were only just above freezing, the rate of saturation of the snowpack has been slow. The period of instability due to a rapid addition of water weight has passed as we will likely see very little precipitation during the day today and only a minor amount tonight. Today’s concern for wet slabs will be due to the slow percolation of meltwater through the snowpack and lubricating layers within the old wind slab or the interface of the wind slab and old ice surface. It is unlikely that the meltwater will impact a layer beneath the old surface due to the amount of melt and previous strength of this layer. Predicting the release of a wet slab today will be very difficult indeed. The trend of the snowpack today will be slowly moving toward instability as the meltwater continues to move deeper, but weather conditions today will keep this rate of change very slow. Heightened avalanche conditions exist 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 8:20 a.m., Tuesday, March 28, 2017. A new advisory will be issued tomorrow.

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

2017-03-28

Avalanche Advisory for Monday, March 27, 2017

This advisory expires at Midnight.

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger today. Central Gully has Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Dangerous avalanche conditions exist. All other forecast areas have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully to identify features of concern.

Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger today. The Sluice and Lip have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Dangerous avalanche conditions exist. All other forecast areas have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully to identify features of concern. The exception to this is the Little Headwall which has Low avalanche danger. Natural and human-triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

AVALANCHE PROBLEM: Today, wind slab will be stressed by additional precipitation and will possibly become saturated, creating wet slab and wet loose avalanche problems. The hazard will increase through the day as the amount of precipitation and temperature increases. This avalanche problem is notorious for its unpredictability and today will be no exception. Looking at the amount of water arriving today, it will likely be at most half an inch by midnight. This is not a huge amount of liquid and combined with the ambient air temperature, may not be enough to overwhelm the cohesiveness of the slab. The areas of greatest concern today are rated Considerable due to the larger possible size of an avalanche as well as the steepness of the slope. Moderate rated areas could have similar but smaller avalanches that could be equally dangerous depending on the terrain.

WEATHER: Starting late in the evening on Sunday, the temperature began flirting with the freezing mark and currently sits at 30F at 6288’ with 40F at 4000’. A three hour period of precipitation, mostly freezing rain, overnight delivered 0.08” of water. After a brief break, precipitation is now falling again and should continue to fall through most of the day in some form. With the temperature remaining around freezing for the day, this precipitation will be a mix of freezing rain, sleet, ice and maybe snow up high with closer to all rain at lower elevations. Wind today will gust briefly this morning to 60mph from the SW and then lower in speed and shift to the W by day’s end.

SNOWPACK: Wind slab that formed at the end of last week covers much of the old, icy bed surface. These wind slabs vary in thickness and hardness depending on the slope aspect. North and NE aspects tend to have more old surface showing, mixed with areas of firm wind slab. While moving through E to S facing aspects, this wind slab is softer and more widespread. Today, all snow will be subjected to various forms of precipitation. It seems likely we may see close to 0.3” of water by early afternoon with a total SWE of 0.5” by the time this advisory expires. As the water percolates into the snowpack, the interface of the wind slab and old surface may become lubricated. This scenario playing out will create wet slabs that are very hard to predict. It is unlikely that the amount of precipitation combined with the temperature today will be enough to create widespread deep instability, but the new load on weak, thin slabs containing loose snow pellets that are poorly bonded to firmer slabs beneath will create plenty of cause for concern in many 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 8:11 a.m., Monday, March 27, 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

2017-03-27

Photos from Sunday, March 26, 2017

Just a taste of Huntington and Tuckerman Ravine this morning. Bluebird skies but no traffic made for a very peacful sunrise.

Huntington Ravine

Damnation Gully

Yale Gully as well as Damnation have pockets of unstable snow near the top that likely reach wall-to-wall. Talking to climbers who traveled in both of these yesterda, they reported knee deep soft snow. These pockets will be heads up today when they start to get cooked by the sun and warm temperatures.

Central Gully was the only gully in Huntington that did not see climbers yesterday. Looking at the pillow of wind loaded snow that exists from top to bottom, I can see why folks went elsewhere.

Odell Gully has lots of ice a the moment. It’s hard to believe it’s almost clising time for the Harvard Cabin.

South Gully has a mix of sastrugi, old surface and few pockets of new snow. A skier reported triggering an isolated pocket of new snow yesterday.

The Overview of Tuckerman

One of my favorite views on this mountain. Hillman’s and the Boott Spur Ridge.

Dodge’s Drop looking very steep at the top

The Duchess

 

Avalanche Advisory for Sunday, March 26, 2017

This advisory expires at Midnight.

 

Huntington Ravine has MODERATE and LOW avalanche danger. Damnation, Yale and Central Gullies 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.

Tuckerman Ravine has MODERATE and LOW avalanche danger. Sluice and Lip will rise to the upper end of Moderate avalanche danger today. Lobster Claw, Right Gully, Center Bowl, Chute, Hillman’s Highway and Lower Snowfields will have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Left Gully and Little Headwall have Low avalanche danger. Natural and human-triggered avalanches are unlikely.

AVALANCHE PROBLEM: Today’s avalanche problem will be driven by heating of the snow by sunshine and warm temperatures. Areas with the most soft wind slabs like Sluice and Lip in Tuckerman Ravine and Central in Huntington have the greatest potential to produce a human-triggered avalanche. As sun warms the snow this morning, the soft snow will become heavy, begin to saturate with water and produce loose wet sluffs and possibly wet slabs large enough to push you around. Today’s warming is not extreme enough to create large wet slabs but skiing will become challenging in the variable “mashed potato” snow and firmer old crust. Areas of old, hard icy snow in Tucks are not widespread but can be found in Left Gully and low in the Chute. This icy surface is generally discontinuous and will create some travel challenges going up or down. Hillman’s Highway has a mix of firmer slabs and softer slabs so expect heavier snow there as well as things heat up.

WEATHER: It’s a blue sky morning, with a current summit temperature of 20 degrees F and WNW winds blowing at 21 mph. Overnight, a low of 14 degrees F was recorded with NW wind reaching 50 mph. Blowing snow was not observed at the summit, suggesting wind transport has not significantly altered our surface conditions since yesterday. Today, temperatures will rise to the mid-twenties and wind will remain light, below 20 MPH, and shift to W and then SW by noon. The ravines will be slightly warmer with less wind. Clouds will build throughout the day as a warm and wet system approaches, but sky cover should remain below 50% through late afternoon.

SNOWPACK: Surface snow conditions remain mixed across our forecast areas. If variety is what you’re after, this is the place to get it. The new snow of mixed forms, including pellets, which fell and drifted late Friday is soft and sluffy in places. While sensitive yesterday, this slab has limited capacity to propagate a crack. This layer exists primarily on south and southeast facing aspects and so is primed for solar warming. Heat and resulting melt water will add to cohesion of the slab and increase potential for a human triggered avalanche as the day progresses. Firmer (1 finger hardness) snow with greater stability that was deposited in the middle of last week is present in much of our terrain. An icy old rain crust, now nearly a month old, is still exposed in wind scoured pockets including nearly half of Left Gully. Beneath these varied surfaces, the snowpack is quite stable. Fun skiing and climbing can certainly be had today. Travelers in our avalanche terrain would do well to retain a level of caution, bringing a partner or two, their beacon, shovel, probe, and critical decision making skills, and avoid sunny aspects if they warm significantly this afternoon.

If you are wondering what a wet slab in Tuckerman Ravine looks like, here is one captured on video that was triggered April 24, 2009. This one was small, but it is events like this that make it so disconcerting when we see people bringing small children into avalanche terrain during periods of elevated danger, as they did yesterday.

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., Saturday, March 26, 2017. A new advisory will be issued tomorrow.

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

2017-03-26

Avalanche Advisory for Saturday, March 25, 2017

This advisory expires at Midnight.

Friends of Mount Washington Avalanche Center is hosting the White Mountain Challenge event today to support our mission. Check out this link for more information on this 9 Ski Mountains in 9 Hours event or to donate.

Huntington Ravine will have CONSIDERABLE and MODERATE avalanche danger. Central, Pinnacle and Odell Gully have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. All other forecast areas have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches possible.

Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. Sluice, Lip, Center Bowl and Chute will have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. All other forecast areas except the Little Headwall have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches possible. Little Headwall has Low avalanche danger. Natural and human-triggered avalanches are unlikely.

AVALANCHE PROBLEM: Wind slabs formed from 7” of new snow on west winds in the past 24 hours keeps the likelihood of human-triggered avalanches in the considerable range. Wind velocities were ideal for loading slopes with an east facing aspect. These slabs are likely to be soft enough to be sensitive to a human-trigger and may be large enough to carry you downhill and possibly bury. Though the threat of natural avalanches is by and large past, the likelihood of human-triggered avalanches makes careful evaluation of snowpack, cautious route-finding and conservative decision making essential. Dense summit fog is currently hampering our ability to make observations so consider each avalanche path to be loaded and waiting for a trigger until you confirm otherwise. Forecast areas with a moderate rating are solidly in that range so assess snow and terrain carefully. A disparity in recorded snowfall between the summit and our forecast elevations gives us some uncertainty about the size of potential avalanches today but this shouldn’t change you travel precautions in avalanche terrain.

WEATHER: Snowfall late yesterday and into the night reached the upper end of forecasted totals, with 6.7 inches recorded at the summit, 2.4” at Hermit Lake and 2.75” at Harvard Cabin in the past 24 hours. Density at Hermit Lake was 17% with a fair amount of rimed particles. This snow fell on West wind blowing near 50 mph and summit temperature has held steady in the high teens to 20F. Wind shifted NW early this morning, is currently decreasing, and is forecast to continue out of the NW with velocities of around 25 mph through tonight. Cloud cover should decrease throughout the day with at least partial clearing likely by late afternoon. If this clearing occurs sooner than expected, solar energy could warm the newly formed wind slabs and increase instability on sunny aspects.

SNOWPACK: Winter continues on Mt. Washington, with new snow transported by west and northwest wind creating today’s layer of concern.  A lack of visibility into the ravines this morning limits capacity for observation.  The recorded wind speeds in the past 24 hours will have built wind slab in areas lee to a west wind, particularly in the upper start zones.  This layer will be relatively soft and sensitive to a human trigger.  The surface beneath this new snow varies.  Firm wind deposited snow and textured sastrugi snow exist over much of the terrain, a layer unlikely but not impossible to fracture and contribute to total mass of snow if an avalanche were to occur in the surface slab.  The Sluice and Lip hold the highest probability of such an avalanche.  Two exceptions to this wind deposited pre-storm surface can be found: A melt-freeze crust in pockets of southerly aspects and an older rain crust in areas scoured by wind earlier this week, particularly Left Gully.

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 7:45 a.m., Saturday, March 25, 2017. A new advisory will be issued tomorrow.

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

2017-03-25

 

Avalanche Advisory for Friday, March 24, 2017

This advisory expires at Midnight.

Huntington Ravine will have CONSIDERABLE and MODERATE avalanche danger. Central, Pinnacle and Odell Gully will have Considerable avalanche danger. Natural avalanches will become possible and human-triggered avalanches will be likely. All other forecast areas have Moderate avalanche danger. Natural avalanches will be unlikely and human-triggered avalanches will be possible.

Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. Sluice, Lip, Center Bowl and Chute will have Considerable avalanche danger. Natural avalanches will become possible and human-triggered avalanches will be likely. All other forecast areas have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches possible.

 AVALANCHE PROBLEM: We are starting out the day with human triggered avalanches being possible only in the steepest portions of Sluice, Lip and Center Bowl, and possibly Central Gully in Huntington, with human-triggered avalanches being unlikely in all other forecast areas due to the strength or lack of continuity of existing wind slabs. East facing forecast areas, particularly upper start zones, will be in the bullseye for developing these wind slabs this afternoon while other aspects will become crossloaded. New snow on increasing west winds will add a bit of stress to existing wind slabs, but the primary problem will be within the new snow. Increasing temperatures and increasing wind speeds will set the stage for increasingly dense slabs over soft new snow falling later this morning. As the day wears on, small to medium sized natural avalanches will become possible in considerable rated terrain. Moderate rated terrain could generate smaller human triggered avalanches and even some small, loose dry natural avalanches in the steepest areas. Reduced visibility and increasing hazard will make conservative terrain choices a good idea today.

 WEATHER: The wind and cold of the past few days abated a bit overnight. Wind has slackened to the 20-30 mph range and shifted to blow from a generally WSW direction. Summit temperature is currently 9 degrees F and is expected to rise to the mid-20’s. Today, a system bearing moisture will move in from the west bringing 1-3 inches of snow this afternoon and evening to Mt. Washington. The NWS has forecast a maximum snow water equivalent of .24” with this storm but available low level moisture and upslope enhancement may bring up to 5”. Westerly wind will increase through the afternoon to approximately 45 mph with gusts in the fifties.

SNOWPACK: Stubborn, firm wind slabs that are thick and well developed in the Sluice, Lip, and other more isolated pockets remain our primary concern this morning, but the coming snow this afternoon will alter these conditions. Wind-textured and similarly firm “sastrugi” snow can be found in much of Chute and Hillman’s as well as South and Escape Hatch. The weeks-old rain crust surface has been largely covered by wind deposits over the past few days, but it still exists as a stable travel option in much of Left Gully and to a lesser extent in other areas.  Additionally, south facing aspects that have been wind scoured following the melt-freeze cycle early this week offer similarly firm, stable snow. The areas below Right Gully and Lobster Claw display this thick melt-freeze surface layer. However, the arrival of snowfall and moderate wind later today should create relatively soft and potentially sensitive new wind slab.  Snow totals will dictate the hazard associated with this new layer. Remember, 2 inches of snow above Tuckerman can easily load Sluice, Lip, Center Bowl and Chute with a much thicker slab.

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

Posted 8:12 a.m., Friday, March 24, 2017. A new advisory will be issued tomorrow.

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

2017-03-24

Avalanche Advisory for Thursday, March 23, 2017

This advisory expires at Midnight.

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

AVALANCHE PROBLEM: Wind slabs remain the primary avalanche problem. Low rated areas are a mix of scoured old surface with areas of heavily wind sculpted and eroded sastrugi snow. You may encounter unstable snow in isolated areas but options to travel on the stable, icy old surface will be plentiful in low rated areas. Stubborn and firm wind slabs may provide easier travel but will also harbor a low probability risk of triggering a stubborn, hard wind slab. Moderate rated areas contain much more smooth wind slab. This typically means that the area was dominated by deposition throughout the wind and snow event. Anticipate firm, continuous thicker slabs in these areas that will also be stubborn and fairly strong but with weaker layers of new snow beneath that bring a higher probability of fracture and failure. As is often the case, these slabs have good bridging power but the possibility of finding and triggering a thin spot in the slab remains. In general, our moderate rated areas are at the lower end of the moderate rating while low rated areas are nudging towards moderate unless you are on the icy, old surface.

WEATHER: The needle on the gauge has once again swung around towards winter. The current temperature on the summit is -17F with 9F at Pinkham Notch. High pressure to our west will keep winds elevated from the northwest, though at a bit lower velocity than yesterday and last night. Expect 70 mph northwest winds to gradually diminish through the day, ultimately blowing around 50 mph with higher gusts, by dark. Temperatures will increase to around 0F during that same time frame. Expect another cold day on the mountain as the epic battle between winter and spring continues.

SNOWPACK: The 5” of snow recorded on the summit on Tuesday night and early Wednesday morning was blown around the mountain and redeposited by the usual, prevailing nuking winds that grace Mount Washington in winter. Several hours of sustained NW winds in the 80’s mph flanked by 18 hours of winds in the high 60’s and 70’s mph tend to beat up snow particles and either blow them out of our start zones or pack them into firm slabs. A combination of fairly low density snow, high wind speeds and a poor bonding surface in the form of the old, icy surface allowed the snow that fell 24-36 hours ago to be scoured and transported through, and out of, many avalanche start zones. That said, remember the forecasters rule of thumb that a typical ridgetop wind can double or quadruple the amount of snow deposited on a lee slope. Our ridgetop is atypical with a large flat expanse in the Alpine Garden that provides enough snow to easily quadruple and more likely octuple (yep, that’s a word) the amount of snow in wind slabs on lee slopes. Again, expect these slabs to be tough and challenging to trigger in most areas but the hard slab that would result would make for a harsh ride downslope. Stay tuned, winter ain’t over yet!

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 8:23 a.m., Thursday, March 23, 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

2017-03-23