Wet avalanche in Tuckerman Ravine

2018-01-14 Lip avalanche in the Headwall of Tuckerman Ravine

Starting late on Thursday, January 11th, southwest flow brought a prolonged period of rain to the region. This rain saturated the thick snowpack that has developed from the 144” of total summit snowfall to date this winter. By Friday night, over 2” of rain had fallen on the summit with temperatures in the 40’s F and nearing 50 F lower on the mountain at Hermit Lake. Sometime Friday the 12th a large wet slab avalanche occurred in the Headwall area of Tuckerman Ravine on a ski run and forecast area known as the Lip. The avalanche forecast for the day warned that, “wet slab avalanches may slide naturally without a human trigger today”, as well as, “the floor of Tuckerman Ravine is particularly threatened by a natural avalanche from the Headwall area.” After inspecting the site, it seems likely that the firm snowpack, weakened by rain, burst like a dam as water pressure built up in the stream channel beneath. The avalanche measured 160’ across the 12-20’ crown and ran 2,000’ with a vertical fall of 500’. By the avalanche size and destructive potential scales, this avalanche is classified as R3D3.5 or medium relative to path and capable of easily destroying wood frame houses or a railroad car.

Aerial few of the debris. People are visible near the end of the debris pile on the left.

This isn’t the first time for this type of avalanche in the Lip. The waterfall here creates this type of avalanche regularly in spring months as snow on the upper mountain melts, flows downhill, and saturates the snowpack. The one pictured below occurred on a busy spring ski day with two people narrowly escaping capture.

VIDEO: 2018-01-14   Aerial of Lip avalanche in the Headwall of Tuckerman Ravine

 

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 Thursday, January 11, 2018

Huntington Ravine has MODERATE and LOW avalanche danger. All forecast areas have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully. North, Damnation and Yale have Low avalanche danger. Watch for unstable snow on isolated terrain features.

Tuckerman Ravine has MODERATE and LOW avalanche danger. All forecast areas have Moderate avalanche danger. Evaluate snow and terrain carefully today. The exceptions to this rating are Left Gully, Lower Snowfields and Little Headwall which have Low avalanche danger. Watch for unstable snow on isolated terrain features.

AVALANCHE PROBLEM: Warm temperatures penetrating existing wind slabs keep danger ratings elevated today. Wet slab and wet loose avalanches should be on your radar today. These avalanche types are notoriously hard to predict but human-triggered avalanches in our warming, softer slabs are possible in steep wind loaded terrain. Natural avalanches of this type seem unlikely but I would not hang around beneath larger slopes today. Low rated areas in Huntington harbor the potential for these problems; while an avalanche there would be small in size, the steepness of the terrain raises the stakes. Moderate rated areas in our terrain are also steep and contain thick enough soft wind slabs to generate an avalanche large enough to bury you. Evaluate snow and terrain carefully if you choose to go into the Ravines.

WEATHER: The summit temperature is currently 34F, Pinkham Notch 31F, with 43F at 4,000’. Light rain and drizzle began on the summit around 1am this morning as air temps pushed to the freezing mark. 3mm of rain was collected at Hermit Lake. Temperatures will continue to rise today as southwest flow brings a January thaw. Highs on the summit will reach 40F. Expect wids to shift SW late in the day from the current W and decrease slightly to the 50-70mph range. Fog will challenge visibility most of the day. Tonight rain will fall more heavily at all elevations with 1.8” of rain currently in the forecast. Expect elevated avalanche danger through the night and into tomorrow due to this rain.

SNOWPACK: Jeff and I took advantage of good visibility and moderate weather yesterday to make some field observations in Tuckerman Ravine. Signs of a widespread avalanche cycle were apparent still in Center Bowl, Chute and Left Gully though the Lip and Sluice areas had reloaded. The softer wind slab which developed primarily Monday and Tuesday was around 4F-1F and variable in thickness as well as density. Similar wind slabs appeared to be present in Central and other moderate rated gullies in Huntington. They proved to be unreactive with only a little graupel mixed into the softer areas of wind slab and no pooling observed in Right, Sluice, Chute or Left Gully. Lots of old pencil hard wind slabs were at the surface in more scoured locations. Snow temperatures 20cm down this morning have already reached -.5C at Hermit Lake.

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 8:10 a.m., Thursday, January 11, 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

2018-1-11

Avalanche Advisory for Wednesday, January 10, 2018

Huntington Ravine has MODERATE and LOW avalanche danger. Yale, Central and Pinnacle Gully have Moderate avalanche danger. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully. All other forecast areas have Low avalanche danger. Watch for unstable snow on isolated terrain features.

Tuckerman Ravine has MODERATE and LOW avalanche danger. All forecast areas have Moderate avalanche danger. Evaluate snow and terrain carefully today. The exceptions to this rating are Lower Snowfields and Little Headwall which have Low avalanche danger. Watch for unstable snow on isolated terrain features. The Little Headwall is skiable out of the bowl though open water in the stream above makes it challenging.

AVALANCHE PROBLEM: Wind slabs which developed in the past couple of days will be the primary avalanche hazard. Widespread, though variable in density, wind slab is the primary hazard due to the larger potential size of an avalanche. These slabs are largest across the Headwall from Sluice to Chute in Tuckerman Ravine and in Central Gully, around the Fan and beneath and in the mid-section of Yale. A new crown line high in Duchess points to the potential danger today. Also on the list of concerns are the snow pellets which fell mid-morning yesterday which pooled and formed a slab in places. These are probably very sensitive to a human trigger. These are more than likely only capable of generating a small avalanche but could be consequential above steep terrain or if they catch you by surprise. Graupel can create sizable slabs beneath steeper ice in Pinnacle, Odell and South as well. Move carefully in the terrain today to stay above both of these hazards and be wary of committing to larger slopes.

WEATHER: It’s a balmy 20 F at Hermit Lake this morning under clear skies. The temperature will continue to rise today, reaching the mid-20s F on the summit. Wind will shift NW to W and increase slightly to the 30-45 mph range which is not likely to transport any more snow into our terrain. Temperatures in our forecast area will likely rise close to the freezing mark though won’t likely contribute to any instabilities. The main concern stems from the 7” of snow which has fallen on loading speed winds in the past 3 days. Looking ahead, expect the dreaded January thaw to strike this week with an ugly ice crust creating slide for life on tap for the weekend.

SNOWPACK: New snow and the resulting wind slabs built over the past several days are mostly sitting above firm slabs. The exception to this would be across the Headwall and in some upper start zones where some softer but unreactive snow had blown in over last weekend. Though not likely to be the weak layer in an avalanche today, this snow could contribute to the volume of snow in an avalanche. Strong wind yesterday moved lots of snow but the wind speeds were not high enough to do a lot of scouring or pack the snow into strong and unreactive slabs like we can get in a prolonged blow. If you plan to take advantage if this nice weather window, bring a solid partner and assess the snow carefully before committing to the slope.

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 8:10 a.m., Wednesday, January 10, 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

2018-1-10

Avalanche Advisory for Tuesday, January 9, 2018

Huntington Ravine has Moderate avalanche danger. Heightened avalanche conditions exist and will continue to develop on specific terrain features. Evaluate snow and terrain carefully to identify features of concern.

 Tuckerman Ravine has Considerable and Moderate avalanche danger. Sluice, Lip, Center Bowl, and Chute will reach Considerable avalanche danger. Careful snowpack evaluation and cautious route finding are essential. Lobster Claw, Right, Left, and Hillman’s Highway have Moderate avalanche danger. Heightened avalanche conditions exist and will continue to develop on specific terrain features. Evaluate snow and terrain carefully to identify features of concern. Lower Snowfields and Little Headwall are the exceptions with a Low rating. Watch for unstable snow on isolated terrain features.

 AVALANCHE PROBLEM: Continued snow showers and wind loading today will continue development of our fresh wind slabs. A lack of visibility this morning following yesterday’s new snow and wind limits our ability to precisely determine size and distribution of these slabs. They will continue to develop today as slab building wind speeds continue and shift NW. We expect human triggered avalanches of small to medium size to be likely today in areas with greatest loading. With visibility possible this afternoon, your field observations of size and distribution for new wind slabs are crucial to determining how and where to minimize your exposure to today’s avalanche problem.

WEATHER: Consistent west wind of 60-70 mph on the summit has been transporting the 2-3” of new snow over the past 24 hours. Snowfall continues this morning and should taper through the day, giving us another 1-2” while wind shifts NW and increases slightly by the end of the day. A partial clearing of cloud cover is forecast for this afternoon. Temperature approached 20F at the summit and exceeded that at Hermit Lake yesterday. We should see slightly colder temperatures today that will drop this afternoon through tonight to just above 0F. Tomorrow temperatures will rise to around the freezing point in the ravines, with partial cloud cover and no measurable precipitation.

SNOWPACK: The new wind slabs that have developed over the past 24 hours, and continue to develop now, lie on firm and more stable slabs formed late last week. Uncertainty is the defining characteristic of today’s avalanche advisory, with a lack of visibility preventing us from determining size and distribution of slabs built since yesterday morning. Snow and NW wind this morning will continue this slab development, and we’re hopeful that increased visibility later today will bring more clarity to our current avalanche problem. We do know that recent and current wind speeds are ideal for turning the handful of inches of new snow into much thicker slabs that would be sensitive to a human trigger. If you have visibility of our avalanche paths today, make thorough observations to determine where and how large these new wind slabs are.

You will see changes to the advisory in the coming weeks and months as we try to find more effective ways to present the avalanche and mountain safety message in an efficient and helpful way. Today’s danger rating section purposely lacks likelihood of avalanche information which you will find in the problem section or in the North American Public Avalanche danger scale posted on kiosks or at the link on this page below the map.

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., Tuesday, January 9, 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

2018-1-9

Avalanche Advisory for Monday, January 8, 2018

Huntington Ravine will reach Considerable and Moderate avalanche danger. Central Gully will reach Considerable avalanche danger. Careful snowpack evaluation and cautious route finding are essential. All other areas will reach Moderate avalanche danger. Heightened avalanche conditions will develop on specific terrain features.

 Tuckerman Ravine will reach Considerable and Moderate avalanche danger today. Sluice, Lip, Center Bowl, and Chute will reach Considerable avalanche danger. Careful snowpack evaluation and cautious route finding are essential. Lobster Claw, Right, Left, and Hillman’s Highway will reach Moderate avalanche danger. Heightened avalanche conditions will develop on specific terrain features. Lower Snowfields and Little Headwall are the exceptions with a Low rating. Watch for unstable snow on isolated terrain features.

 AVALANCHE PROBLEM: New wind slabs building later today and tonight are our primary concern. The few inches of snow will be transported by ideal wind speeds to create sensitive slabs in lee areas by the end of the day. If we receive the higher end of forecast snowfall, human triggered avalanches should become likely in areas receiving the greatest wind loading by the end of the forecast period. Your likelihood of triggering an avalanche in the dense and supportable older surface slab that precedes today’s storm remains unlikely in all but highest rated areas.

WEATHER: Snow showers which began last night should intensify slightly through the day. Mixed forecasts lead us to expect 3” or more of snow accumulation today on W wind of around 60 mph that will increase slightly into tonight. Temperatures have been slowly climbing since yesterday and will likely hit the upper teens or warmer this afternoon. Snowfall is forecast to taper off late tonight to at least a partial clearing tomorrow afternoon. Wind should remain constant with only slightly cooler temperatures tomorrow.

SNOWPACK: Today’s snow falls on a largely firm surface layer that has been hammered by sustained wind speeds in the neighborhood of 100 mph over the past few days. Potential for you to trigger an avalanche in the older layer remains possible at best, and avoiding travel on or below any significant new wind slabs developing today will provide a safer alternative as hazards increase. It’s worth noting snow total forecasts for today vary widely and that today’s danger ratings reflect potential for a wind slab avalanche problem developing through the forecast period which ends at midnight tonight. If we see the lower end of forecast snowfall our avalanche danger will not increase to as great a degree. That said, blowing snow and limited visibility could hamper your ability to judge wind slab development in terrain above you.

You will see changes to the advisory in the coming weeks and months as we try to find more effective ways to present the avalanche and mountain safety message in an efficient and helpful way. Today’s danger rating section purposely lacks likelihood of avalanche information which you will find in the problem section or in the North American Public Avalanche danger scale posted on kiosks or at the link on this page below the map.

2018-1-8

Avalanche Advisory for Sunday, January 7, 2018

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

Tuckerman Ravine has MODERATE and LOW avalanche danger. Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Evaluate snow and terrain carefully. All other forecast areas have Low avalanche danger. Watch for unstable snow on isolated terrain features. The Little Headwall may still have open water.

 

AVALANCHE PROBLEM: Moderate rated slopes contain firm wind slabs. These slabs are mostly firm (1F-P) and probably stubborn but, as always, careful evaluation before committing to a slope would be good practice today. Lots of visual cues exist to indicate slopes are wind hammered due to the continuous wind transport of snow grains on the ground. Low rated areas are more eroded down to older hard slabs due to the scouring action of avalanches followed by strong winds. The same smooth slabs are also present in Low rated areas but are smaller and present more opportunities to get around them. Natural avalanche activity in unlikely in all areas today but evaluate snow and travel carefully, even in areas with a Low danger rating.

 

WEATHER: The temperature is currently -17F on the summit with northwest winds at 80 mph range. Winds have blown steadily from the west-northwest and northwest in the 80-100 mph range over the past 24 hours with even higher gusts. No new snow was recorded in the past 24 hours on the summit. Skies are currently clear with some thin summit fog and wind transported snow at the ridgetops. Winds will diminish further to the 50-70 mph range today and shift to the west. The temperature at the summit will climb to near 0F through the day under sunny skies.

 

SNOWPACK: So far, early morning light has revealed possible signs of avalanche activity in Chute and Left Gully in Tucks and Central Gully in Huntington. Debris isn’t obvious though due to the continuous wind hammering that our terrain has received in the past 24 hours. The Lip has a distinct crown line but has reloaded quite a bit. Our low rating comes today with a reminder that low avalanche danger doesn’t mean no avalanche danger. We are still dealing with a midwinter snowpack with lots of variability across slopes and elevations. Use safe travel practices and only expose one person at a time and carry your avalanche rescue equipment just in case. A crown line in one of the gullies (Main?) in Gulf of Slides just above the mid slope choke point was also observed this morning.

 

You will see changes to the advisory in the coming weeks and months as we try to find more effective ways to present the avalanche and mountain safety message in an efficient and helpful way. Today’s danger rating section purposely lacks likelihood of avalanche information which you will find in the problem section or in the North American Pubic Avalanche danger scale posted on kiosks or at the link on this page below the map.

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 7, 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

2018-1-7

Avalanche Advisory for Friday, January 5, 2018

Huntington Ravine has CONSIDERABLE and MODERATE avalanche danger. Central, Pinnacle, Odell, Escape Hatch and South have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. North, Damnation and Yale have Moderate avalanche danger. Natural avalanches are unlikely and human- triggered avalanches are possible.

Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. Lobster Claw, Right, Sluice, Lip, Center Bowl, Chute, Left and Hillman’s Highway have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Lower Snowfields has Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. The Little Headwall may still have open water. 

AVALANCHE PROBLEM: Wind shifting to the west today will create more wind slab in our terrain. Much of the 16” of new snow yesterday remains tucked in lee features in the alpine zone and will be transported by today’s west wind. This wind shift has a history of prolonged loading and today’s forecast is no different. Anticipate significant loading to continue from a new direction as the wind increases today and digs into the drifts and snowfields deposited by yesterday’s wind. Another concern are the dense wind slabs pounded into our terrain by last night’s howling wind. Those slabs remain a concern, especially in areas of Tuckerman Ravine with a more southerly aspect. These more stubborn slabs may fail under the weight of wind loaded snow today, with or without a human trigger. 

WEATHER: Snowfall totals collected from two snow study plots just below treeline show 13” to 16” of snow fell in the past 24 hours. During that period, wind wrapped around from the east through the north and ramped up into the 70’s and 80’s mph as it shifted though the northwest with a peak gust of 122 mph from the NNW. As the low pressure system pulls away today, wind will increase again and shift west. 1-3” inches of upslope snow, available low density snow on the ground and the shifting and increasing wind are the primary drivers of our avalanche problem today. Temperatures will fall into the -25F range on the summit today which will create a different set of problems.

SNOWPACK: Limited visibility is hampering our ability to observe recent avalanche activity but it isn’t too much of a stretch to assume the weak layer was yesterday’s new snow. Ice crust from the Christmas storm was largely swept out in many areas or is deeply buried and so is not much of a player at present in our steep terrain. The bed surface for yesterday’s activity was likely the firm, squeaky pencil hardness slab which were prevalent in our terrain and seen in our recent video posts. Some previously existing softer snow in the Sluice, Lip and Center Bowl could contribute to the volume of snow from an avalanche in the Bowl, if it hasn’t slid already. Yesterday’s wind direction most likely filled in areas low in the forecast area such as the Fan in Huntington and Lower Snowfields in Tuckerman so remain heads up even in this lower angled terrain. As mentioned above, Lobster Claw and Right Gully, which are often quick to stabilize, received a good wind loading and should be evaluated carefully.

The Lion Head Winter Route is the safer route to the summit on the east side. Both the Tuckerman and Huntington Ravine Trails as well as the Lion Head Summer Route pass through several avalanche paths and are challenging mountaineering routes with significant avalanche hazard.

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 8:23 a.m., Friday, January 5, 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

2018-1-5