Avalanche Advisory for Wednesday, January 17, 2018

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger. Central Gully has Considerable avalanche danger. Dangerous avalanche conditions exist. Cautious route-finding, conservative decision-making are essential today. All other forecast areas have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully.

Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. Lip, Center Bowl, Chute, Left and Hillmans Highway have Considerable avalanche danger. Dangerous avalanche conditions exist. Cautious route-finding, conservative decision-making are essential today. Lobster Claw and Right Gully have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully. Lower Snowfields has Low avalanche danger due to lack of snowcover.  The Little Headwall is mostly open water or waterfall ice. 

AVALANCHE PROBLEM: Wind slab may develop this afternoon as light density snow is blown on westerly and southwesterly winds. Though on the smaller side, these avalanches will likely be sensitive to human triggers. Dry loose avalanches or sluffs are also likely to occur today and could entrain enough snow to knock you off a stance in steep terrain. Both avalanche types are developing on top of a hard, icy crust that will be not only a slippery bed surface but will also create slide-for-life conditions. Due to the light snowfall today, the size and distribution of these avalanche types will grow through the day and depend on receiving the forecast amount of snow. The most imminent threat that will remain constant throughout the day is the icy crust and the potential for a long sliding fall into rocks, stout bushes and holes melted into the snowpack.

WEATHER: Light snow continues this morning after about 2” of snow fell on the summit in the past 24 hours. Down lower at Hermit Lake, 3.5 cm of snow was recorded on the storm board at 6:30 this morning. West-southwest winds are currently light at around 25 mph but are expected to increase later in the day. 2-4” more snow is forecast today with 2” more tonight. The size and distribution of the wind slab avalanche problem depends upon the today’s snowfall totals and wind speeds. Timing of the increase in wind speeds later in the day is unclear, though a minor increase will disproportionately increase avalanche danger level. Anticipate low visibility today due to summit fog and snow.

SNOWPACK: As mentioned above, our snowpack is hard. A prolonged warming spell with rain turned the upper portion of the snowpack into a knife hardness crust with the bridging power of structural steel. The recent warmup ended with a period of freezing rain that glazed trees and snow surfaces at our elevation with ice. While weaker snow exists deeper in the snowpack, it is not at all a player in any instabilities developing today. The blown out portion of the Lip and the hard, refrozen debris pile remain dominant features in Tucks. The recent rain and return of cold temperatures has been a boon to ice climbers. The Sherburne Ski Trail remains an icy mess, complete with a wall-to-wall field of frozen boot tracks in one section.  It will likely need more than today’s snowfall to create softer snow conditions. Crampons are needed for any steep terrain today.

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This bulletin 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 8:15 a.m., Wednesday, January 17, 2018. A new advisory will be issued tomorrow.

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

2018-1-17

Avalanche Advisory for Tuesday, January 16, 2018

Huntington and Tuckerman Ravines have LOW avalanche danger. Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. The Little Headwall is an open stream and is not rated.

AVALANCHE PROBLEM: Today’s limited snow showers falling on a very hard refrozen upper snowpack keep our avalanche concerns to a minimum. The timing of the incoming snowstorm looks as though insufficient snow will fall to merit new stability problems before this advisory expires at midnight. Other hazards should play a greater role in your travel decisions today, which include but are not limited to:

  • Long sliding falls are all but certain if you lose your footing high on a steep slope. Crampons, ice axe, and your ability to use them are essential for travel on snow slopes today. Microspikes are an effective tool on icy trails but are no substitute for crampons on firm snow slopes. Realize that the hardness of surface snow will make arresting a fall with an ice axe very challenging and that recently exposed rocks elevate the consequences of such a fall.
  • Ice dams blowouts are common on our ice climbs in conditions like this when significant water flows under ice. These can cause a myriad of problems and have been the source of fatal accidents.

WEATHER: A trace of snow early this morning is bringing a wintry look to the area but has not altered our firm surface snow conditions. Today will become increasingly cloudy as snow showers develop that could bring up to an inch of new snow. Temperature should remain around 10F on the summit, dropping slightly later today. West wind is forecast to increase towards 50 mph before shifting SW and decreasing tonight. Tomorrow will bring a handful in inches of snow with continued moderate SW wind.

SNOWPACK: A thick layer of hard refrozen snow encapsulates our remaining snowpack. Thickness of this layer varies spatially with the degree to which recent rain saturated the upper snowpack, but seems to be at least a few inches to over a foot. Needless to say, this is a supportable crust in the alpine and requires good crampon and ice axe skills to travel in steep terrain. Snow today should not accumulate enough to warrant new stability issues with potential to harm a person. This could change tomorrow following more snowfall. As discussed above, other mountain hazards are quite relevant today. Though disappointing for snow lovers, the weather of the past week illustrated the mountain’s ability to produce extraordinary avalanche events, as evidenced by Friday’s massive wet snow avalanche. It’s an important reminder of the power of snow on a steep slope.

The John Sherburne Ski Trail has a large area where flowing water melted all snow. Combined with firm conditions and a rough refrozen snow surface in places, it’s not a great ski option. For travel on foot, areas of water flowing across and down the trails had similar though less drastic effects. The Lion Head Winter Route remains open with varied conditions including snow, ice, dirt, and rock.

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This bulletin 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 7:30 a.m., Tuesday, January 16, 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

2018-1-16

Avalanche Advisory for Monday, January 15, 2018

Huntington and Tuckerman Ravines have LOW avalanche danger. Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. The Little Headwall has again become a waterfall and is not rated.

AVALANCHE PROBLEM: The significant melt freeze event of the past few days coupled with continued cold temperatures greatly reduced instability in our snowpack. Natural and human triggered avalanches are unlikely today, with other hazards currently of greater concern for those travelling in our terrain. The following hazards are particularly noteworthy today:

  • Long sliding falls are all but certain if you lose your footing high on a steep slope. Crampons, ice axe, and your ability to use them are essential for travel on snow slopes today. Microspikes are an effective tool on icy trails but are no substitute for crampons on firm snow slopes. Realize that the hardness of surface snow will make arresting a fall with an ice axe very challenging and that recently exposed rocks elevate the consequences of such a fall.
  • Undermined snow and water running under snow and ice is a concern with water continuing to flow despite cold temperatures. Watch for low areas that could be draining water, listen for water flowing under the snow and ice, and remember that significant water flows down our ice climbs.
  • Ice dams and blowouts of ice are common on our ice climbs in conditions like this when significant water flows under ice. These can cause a myriad of problems and have been the source of fatal accidents. Be particularly cautious of screw, tool, and foot placements in regards to this issue.

WEATHER: It’s a colder morning at Pinkham than at the summit, with a temperature inversion holding air just below 0F at low elevations. It’s currently 11F on the summit. Temperature is forecast to increase by just a few degrees on the summit today and decrease to around 0F tonight. Southerly wind approaching 30 mph at the top of the mountain should feel relatively calm in the ravines. Partially cloudy skies should become mostly cloudy tonight. Tomorrow brings increased cloud cover as a system approaches late in the day with potential to give us a few inches of new snow by Wednesday morning.

SNOWPACK: The strong temperature swing Saturday that followed our significant rainstorm resulted in hard refrozen surface snow and generally stable conditions throughout our snowpack. As mentioned above, this means full on slide for life conditions in our steep terrain. Snow depth and coverage has decreased significantly. North, Damnation, Yale, South, and Escape Hatch gullies in Huntington Ravine do not hold continuous top to bottom snow. The same is of course true for the open stream that is the Little Headwall. Snow in other areas has become quite narrow, and the tops of a number of gullies have melted to rock. In Tuckerman, Right Gully was hit particularly hard while other areas faired reasonably well and continue to hold top to bottom snow. It’s a drastic shift from the plentiful dry snow of early last week and from the conditions which produced Friday’s massive wet avalanche in the Lip of Tuckerman Ravine.

The John Sherburne Ski Trail has a large area where flowing water melted all snow. Combined with firm conditions and a rough refrozen snow surface in places, it’s not a great ski option. For travel on foot, areas of water flowing across and down the trails had similar though less drastic effects. The Lion Head Winter Route remains open with varied conditions including snow, ice, dirt, and rock.

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This bulletin 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 7:30 a.m., Monday, January 15, 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

2018-1-15

Avalanche Advisory for Sunday, January 14, 2018

Huntington and Tuckerman Ravines have LOW avalanche danger. Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. The Little Headwall has again become a waterfall and is not rated.

 AVALANCHE PROBLEM: A solid refreeze of our heavily wetted snowpack has greatly increased stability which will hold through this forecast period. Natural and human triggered avalanches are unlikely at best. If you’re in our terrain today, a number of other hazards should make avalanches a lesser concern:

  • Long sliding falls are all but certain if you lose your footing high on a steep slope. Crampons, ice axe, and your ability to use them are essential for travel on snow slopes today. Microspikes are an effective tool on icy trails but are no substitute for crampons on firm snow slopes. Realize that the hardness of surface snow will make arresting a fall with an ice axe very challenging and that recently exposed rocks elevate the consequences of such a fall.
  • Undermined snow and water running under snow and ice is a concern with water continuing to flow despite cold temperatures. Watch for low areas that could be draining water, listen for water flowing under the snow and ice, and remember that significant water flows down our ice climbs.
  • Ice dams and blowouts of ice are common in conditions like this when significant water flows under ice in ice climbs. These can cause a myriad of problems and have been the source of fatal accidents.

 WEATHER: Seasonable cold temperatures have returned following several days of very warm and wet weather. Over 48 hours of above freezing temperatures and 3” or more of rainfall wreaked havoc on the mountain. Areas farther west saw several inches of snow yesterday, but we received only negligible amounts of frozen precipitation. Expect today to be clear and cold with temperatures in single digits F. Summit wind should stay in the 20-30 mph range. Tomorrow is forecast to bring slightly warmer temperatures, similar wind speeds, a few more clouds, and no precipitation.

SNOWPACK: The significant rainstorm of the last few days drastically changed conditions top to bottom on the mountain. The waterfall area of the Lip produced a massive wet snow avalanche that entrained a significant amount of snow and fully covered the floor of Tuckerman Ravine with debris. A strong refreeze since yesterday afternoon has stabilized our snowpack, but this avalanche serves as an excellent reminder of what heavy rains on snow can produce. Outside of this avalanche debris, much of our terrain hold a hard, icy, and fairly smooth snow surface. Coverage has decreased with more rocks and bushes exposed, but after a snowstorm or two the skiing shouldn’t be bad.

The John Sherburne Ski Trail has large areas where flowing water melted all snow. We highly recommend that skiers and snowboarders avoid it until filled in with more snow. For travel on foot, areas of water flowing across and down the trails had similar though less drastic effects. The Lion Head Winter Route remains open, though significant loss of snow will make travel challenging.

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This bulletin 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, January 14, 2018. A new advisory will be issued tomorrow.

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

2018-1-14

Avalanche Advisory Saturday, January 13, 2018

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger. Central, Pinnacle, Odell, South, and Escape Hatch have Considerable avalanche danger. Dangerous avalanche conditions exist. Cautious route-finding, conservative decision-making are essential today. North, Damnation and Yale have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully.

Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. All forecast areas have Considerable avalanche danger. Dangerous avalanche conditions exist. Cautious route-finding, conservative decision-making are essential today. The exception to this rating is the Lower Snowfields which have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully. The Little Headwall is likely a raging river with avalanche danger being the least of your concerns.

AVALANCHE PROBLEM: Wet Slab and Wet Loose avalanches will continue to be our primary avalanche problem until our snowpack solidly refreezes later today or tonight. Peak instability, with possible natural avalanches and likely human triggered avalanches, may have already passed since this warm and wet storm started early yesterday. That said, the nearly 1” or rain in the past 6 hours could be causing continued instability. Temperatures that are currently dropping will allow our avalanche danger to decrease significantly through the day. If rain switches to snow early and pushes the higher end of forecast snow accumulation, we could see areas of new snow instability develop by the end of the day, though other hazards like undermined snow and firm snow conditions will likely be of greater concern.

Additionally, higher volume watercourses such as the main waterfall in the Lip as well as Central and Pinnacle Gullies in Huntington, among other streams, will undermine snow and create fall or drowning hazards. It is likely that the main waterfall/Open Book area along with the Little Headwall waterways have opened up. Both of these areas have been the scene of serious or fatal accidents.

WEATHER: The past 24 hours has brought nearly 2” of rain to the mountain, with nearly an inch in the past 6 hours. Though temperatures are currently hovering around 32F at elevations 4000’ and below, with warm air near 40F holding at the summit, our snow surface has yet to freeze. It will become increasingly cold from now until tomorrow morning with lows around 0F tonight. The timing of this cold air will determine what form our continued precipitation will take as it falls. If the current rain turns to snow sooner than later we could see several inches of snow or more by the end of the day. If warm temperatures hold a few more hours, we will likely see much less snow accumulation.

SNOWPACK: The heavy rain over the past 24 hours will be drastically altering our snowpack. A lack of visibility into the terrain since this storm began limits our ability to identify specific changes to our surface snow. We expect that wet avalanches have occurred naturally and may continue until a solid freeze later today. Prior to the rainstorm, layers of varying density though mostly firm wind slab existed across much of our terrain. A buried crust formed Dec. 23rd was also continuing to hang around in areas it had not been ripped out by avalanches. Rain and meltwater percolating through the snowpack will first be the cause of natural wet slab and wet loose avalanches, but by the time our snowpack refreezes this water will likely have resulted in greater uniformity.

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This bulletin 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 7:50 a.m., Saturday, January 13, 2018. A new advisory will be issued tomorrow.

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

2018-1-13

Avalanche Advisory for Friday, January 12, 2018

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger. All forecast areas have Considerable avalanche danger. Dangerous avalanche conditions exist. Cautious route-finding, conservative decision-making are essential today. North, Damnation and Yale have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully.

Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. All forecast areas have Considerable avalanche danger. Dangerous avalanche conditions exist. Cautious route-finding, conservative decision-making are essential today. The exceptions to this rating are the Lower Snowfields and Little Headwall which have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully.

 AVALANCHE PROBLEM: Wet slab avalanches may slide naturally without a human trigger today. As rain and warm temperatures continue to reach deeper into the snowpack, the likelihood and size of an avalanche will increase. While relatively slow moving, this avalanche type is particularly dense and potentially destructive. The floor of Tuckerman Ravine is particularly threatened by a natural avalanche from the Headwall area.

Additionally, higher volume watercourses such as the main waterfall in the Lip as well as Central and Pinnacle Gullies in Huntington, among other streams, will undermine snow and create fall or drowning hazards. It is likely that the main waterfall/Open Book area will open up today along with the Little Headwall stream course. Both of these areas have been the scene of serious or fatal accidents.

 WEATHER: Another day of warm temperatures and rain are on tap today. As is often the case on the mountain, precipitation amounts vary widely by elevation and location. Hermit Lake received only a trace of rain in the past 24 hours with .42” falling on the summit during the day yesterday and more last night. Another ¾”-1” of rain at minimum is expected to fall through the daylight hours with the heaviest rain falling later this morning and in the afternoon. Current temperatures are 40 F on the summit, 45 F at Hermit Lake, and high 40’sF at Ravine elevations on the Auto Road. Southwest winds will increase to the 70-90 mph range with gusts over 100 mph then diminish a bit in the afternoon. Temperatures will begin to fall later tonight and dip below freezing by sunup tomorrow.

SNOWPACK: Our snowpack had some soft slabs in lee areas of a northwest wind day before yesterday. These slabs were first to saturate and may have already avalanched in some areas. Beneath that snow a firmer pencil hard slab was widespread through the terrain. It seems likely that this part of the snowpack will be the bed surface along with some isolated areas of ice crust that have survived the avalanche cycles since the December 23-24 freezing rain event. It is also possible that our snowpack adjusted to the increased stress of rain saturated and heat weakened snow with no avalanches occurring anywhere. Such is the nature of this type of avalanche problem. In either case, there are plenty of reasons to avoid traveling in avalanche terrain today, the least of which may be the potential for avalanches.

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This bulletin 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 7:35 a.m., Friday, January 12, 2018. A new advisory will be issued tomorrow.

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

2018-1-12

Avalanche Advisory for Sunday, December 31, 2017

Huntington Ravine has MODERATE and LOW avalanche danger. Central, Pinnacle, Odell, South, and Escape Hatch have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully, identify features of concern. North, Damnation, and Yale gullies 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, Chute, Left, and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully, identify features of concern. Lobster Claw, Right Gully, Lower Snowfields, and the Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

 AVALANCHE PROBLEM: Variability in our upper snowpack keeps ratings at Moderate for much of the terrain today, with wind slab continuing as our primary concern. We expect greatest instability in the smooth slabs commonly existing between ½ and ¾ of the way up much of our terrain. Our upper start zones are largely wind hammered to a firm and textured snow surface which would be hard pressed to produce an avalanche. Thin areas of the softest and smoothest pockets of wind slab have the greatest potential to produce a human triggered avalanche today. Low rated areas will tend to offer more options to avoid today’s avalanche problem. Don’t become complacent due to firm feeling snow. Dig and probe before committing to travel on wind slabs.

 WEATHER: High pressure continues to allow arctic air to dominate our area. Temperatures in the negative 20’s F are currently combining with wind gusting over 80 mph on the summit. No significant slab building snow is being transported. We should see quite consistent weather today through tomorrow, with summit temperatures in the teens below zero and NW wind around 60 mph. Partial cloud cover and no measurable precipitation is expected. A break in these frigid conditions will hopefully occur later in the week. A potential low pressure system Thursday into Friday could bring temperatures well above zero and new snow.

SNOWPACK: Arctic temperatures slow stabilization at best and also have the potential to create facets which can act as a weak layer. While bonds beneath surface slabs are likely growing in some areas, potential exists for facet growth and weakening of bonds in other areas. The crust formed days before our Christmas storm continues to be a player where beneath the surface and not wiped out by avalanches. In short, the upper portion of our snowpack has high variability. This variability can be difficult to visually discern except for areas where the old crust is present at the surface. As a result we have not lowered ratings since yesterday. If you brave the chilling conditions, be sure to consider the consequences of even the smallest avalanche or any accident.

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This bulletin is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
• Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast. For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or Harvard Cabin.
• Posted 7:40 a.m., Sunday, December 31, 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

2017-12-31

Avalanche Advisory for Saturday, December 30, 2017

Huntington Ravine has MODERATE and LOW avalanche danger. Central, Pinnacle, Odell, South, and Escape Hatch have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully, identify features of concern. North, Damnation, and Yale gullies 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, Chute, Left, and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully. Lobster Claw, Right Gully, Lower Snowfields, and the Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

 AVALANCHE PROBLEM: Firm and generally stubborn wind slabs are the primary avalanche problem today. These firm slabs will have good bridging strength in lots of areas but realize that thin spots, convexities and other trigger points may still be lurking.  Evaluate snow and terrain carefully as you move around the terrain today. Recent avalanche activity in much of our terrain has swept out the ice crust built from the rain event last weekend but lower angled areas which didn’t avalanche may still hold this potentially problematic layer. You’ll find firm (1F) but mostly smooth slabs in most of our terrain that hasn’t seen the scouring or sastrugi building action of the wind near the ridgetops. Low rated areas have fewer areas of concern and provide more terrain opportunities to avoid them.

WEATHER: Yesterday brought a respite of sorts from the bitter cold at higher elevations, as a temperature inversion allowed the mercury to peak at 7F on the summit and creep into the low teens at Hermit Lake. Temperatures dropped to the teens below zero last night and should stay below zero today. NW wind around 30 mph on the summit could increase to around 50 mph tonight. We will see intermittent cloud cover with a chance of a trace of snowfall. Temperature will drop to around 20 below tonight on the summit and rise only a little tomorrow. Expect increasing wind speeds to compound tomorrow’s frigid conditions.

SNOWPACK: High winds mid-week caused a wide-spread avalanche cycle in the steep terrain of our forecast area, ultimately creating rugged and relatively hard to trigger wind slabs. There are plenty of thin spots in these firm (1F) slabs due to varying thicknesses so human-triggered avalanches remain possible in many areas. Evaluate snow and terrain carefully to identify poor bonding to the ice crust or possibly early faceting. The previous avalanche cycle in our steep terrain cleaned out big sections of this ice crust in some areas like below the ice in the Lip and below the choke in Left Gully but some areas of the crust may remain. An observer in the Ammonoosuc Ravine reported propagation potential on early facets in one stability test (with no ice crust in the pit) and another observer reports that most of the Gulf of Slides did not avalanche in the widespread mid-week cycle. This is a pertinent fact pointing to the possibility of the ice crust with soft (4F-F) snow lurking in large portions of those gullies.  Dig and probe frequently and recognize that cold temperatures and crusts create a dynamic snowpack that could become reactive to human triggers.

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This bulletin 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, December 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

2017-12-30

Avalanche Advisory for Friday, December 29, 2017

Huntington Ravine has Moderate and Low avalanche danger. Central, Pinnacle, Odell, South, and Escape Hatch have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully, identify features of concern. North, Damnation, and Yale gullies 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, Chute, Left, and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully, identify features of concern. Lobster Claw, Right Gully, Lower Snowfields, and the Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

 AVALANCHE PROBLEM: Firm and relatively stubborn to trigger wind slabs that exist over much of our terrain are our primary avalanche problem today. Realize that this layer will be easiest to trigger in thinner and/or softer areas, which is difficult to visually discern when route finding. Today remains a low probability, high consequence risk situation for a number of reasons. Bitterly cold weather will complicate any problem and a number of our avalanche paths continue to have nasty runouts. Continue to realistically consider “what if” scenarios in your travel planning.

 WEATHER: It’s cold and will remain so through the forecast period. The summit is currently experiencing a slight respite from negative double digits, with temperatures hovering just above 0F, though the mercury will drop towards the teens below zero through the day. NW wind below 30 mph will push higher this evening, possibly exceeding 50 mph overnight. Increasing clouds should produce snow showers that will bring a trace to 2” of new snow. Tomorrow will bring similar temperatures and NW wind with a lesser chance of snow accumulation.

SNOWPACK: Precipitation and wind over the past week has resulted in further progression of our terrain towards full winter snow cover. Wind loading and the resulting avalanches have contributed significantly towards filling in the lower portions of our avalanche paths. We expect that many of the avalanches in the past week wiped out the 1-2 cm crust which formed last Saturday, though exceptions can likely be found. Where avalanches did not occur, the crust which lies over soft snow (4F-F hardness) still exists under our current firm surface slabs. These current firm and relatively stubborn slabs are our primary avalanche problem today. We do still harbor concern for deeper instability in the form of the soft layer under last Saturday’s crust. If the surface slab was triggered, the possibility remains for an avalanche to step down and entrain significant snow.

The Lion Head Winter Route is open and the preferred route to the summit from the east side.

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This bulletin 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., Friday, December 29, 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

2017-12-29

Avalanche Advisory for Thursday, December 28, 2017

This advisory expires at Midnight.

Huntington and Tuckerman Ravine have MODERATE avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible in all forecast areas. Evaluate snow and terrain carefully. Lower Snowfields and Little Headwall in Tuckerman have Low avalanche danger due to lack of a developed snowpack. Watch for unstable snow on isolated terrain features such as Dead End and Duchess above the Lower Snowfields.

 AVALANCHE PROBLEM: High winds overnight continued to transport snow into our forecast area. Sustained NW wind in the 80s and 90s mph worked over the snow last night. These wind speeds have a history of scouring the northern gullies in Huntington and packing dense and stubborn wind slabs in other areas of both Ravines. Unfortunately, limited visibility this morning gives us no opportunity to confirm. Many areas like the northern gullies in Huntington and many forecast zones in Tuckerman are probably closer to a Low rating due to the density and stubbornness of wind slabs. If you chose to travel into the terrain today, be on the lookout for these dense slabs which may have formed over a weaker layer of storm snow.

 WEATHER: Very cold temperatures will make for challenging conditions today. Harvard Cabin temperature is currently -13F with a low reached last night of -17F. Summit temps have rebounded to -31 F from an overnight low of -33 F. Wind speeds are currently in the mid-80’s mph from the NW. Wind should relax to the 35-50 mph range this afternoon reaching mid 40’s mph by sundown. Anticipate the mercury climbing slowly towards -10 F or so on the summit in the afternoon.

SNOWPACK: The summit recorded no new snow yesterday though a brief visit to Tucks yesterday confirmed that moderate wind transport of snow on the ground continued. For those who haven’t been keeping track, the summit has recorded 80” of snowfall this month. Currently there is 76cm on the ground at the Harvard Cabin snow plot. If you are inclined to multiple winter sports, the pendulum seems to be swinging from skiing and riding and back towards mountaineering and ice climbing, though soft snow can probably still be ferreted out in the trees.

 The Lion Head Winter Route is open and the preferred route to the summit from the east side. The John Sherburne ski trail has good coverage with limited areas scoured down to the icy base. There are still a few rocks just submerged in the snow so easy turns are advisable.

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This bulletin 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 7:35 a.m., Thursday, December 28, 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

2017-12-28