Post-nor’easter

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Avalanche Advisory for Saturday, December 31, 2016

This advisory expires at Midnight tonight.

All forecast areas in Huntington Ravine have MODERATE avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully.

 Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. Sluice, Lip, Center Bowl, Chute and Hillman’s Highway have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Lobster Claw, Right Gully and Left Gully have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Evaluate snow and terrain carefully. Lower Snowfields and Little Headwall are not rated due to a lack of snow but look for overhead hazard in Lower Snowfields which is remains tree covered except beneath Duchess.

AVALANCHE PROBLEM: Large, smooth but stiff and probably stubborn wind slabs exist throughout our Considerable rated terrain remain in the wake of the 24” of snow that fell in the past 36 hours. Our Considerable danger ratings are more likely straddling the line with a Moderate danger rating due to a somewhat reduced likelihood of natural avalanches. In Huntington, our danger rating of Moderate is edging towards Considerable in many areas like in Central, the approach and second pitch to Pinnacle, and low on approaches to northern gullies. It is worth remembering that remaining wind slabs may be sitting in top of an icy crust and probably not all that well bonded. Protect yourself with safe travel techniques and evaluate suspect snow and terrain features. Softer and more sensitive wind slabs are also something to look for and avoid. Steep but more protected terrain may hold sensitive pockets more easily triggered by a person.

WEATHER: The temperature on the summit is -8F with wind from the west around 60 mph. Wind transported snow continues to blow into our terrain, particularly in Tuckerman Ravine. Wind will shift to the SW today and decrease to 35-50 mph which will effectively stop wind transport of snow. Air temperature will rise to 10F on the summit. Visibility is already diminishing due to fog. Expect clouds to descend on the summit by nightfall as another round of precipitation begins, potentially bringing 3-6” more snow overnight.

SNOWPACK: While no crown lines exist to tell the tale of the avalanche cycle that occurred yesterday, it is only because of the continued loading of new and wind transported snow covered them all up. Debris is obvious and extended well out into the floor of Tuckerman Ravine and ran 200m beyond previous avalanches this season. The debris is very deep and ran across the trail and into the woods ending about 100 yards above the Connection Cache. This is a powerful reminder that you are well into avalanche terrain if you go beyond the Cache to “look around”. In Huntington, avalanche debris remains visible well below Central Gully and clearly rounded the corner in Hillman’s Highway. The ice crust remains a player in our stability picture even though it is buried most everywhere in our forecast area. Crusts serve not only as a slick bed surface, but also as a layer to develop weak, sugary facets just above and below.

The Lion Head Winter Route is open and the most direct route to the summit. The Tuckerman Ravine Trail bridge is completed enough to allow traffic again. Please be careful of construction debris near crossover 7 on the Sherburne Trail when skiing or riding.

Please Remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
  • Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
  • For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.
  • Posted 8:25 a.m., Saturday, December 31, 2016. A new advisory will be issued tomorrow.

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

2016-12-31

 

Avalanche Advisory for Friday, December 30, 2016

Huntington Ravine and Tuckerman Ravine have HIGH avalanche danger. All forecast areas will have HIGH avalanche danger today. Natural avalanches are likely and human-triggered avalanches very likely. Very dangerous avalanche conditions exist. Travel in avalanche terrain is not recommended.

AVALANCHE PROBLEM: Widespread and possibly large wind slab avalanches will almost certainly occur today in our forecast areas. Travel beneath steep open slopes and gullies will put you in the bullseye for being struck and buried by these avalanches. The existing icy bed surfaces and prior avalanche debris will allow these avalanches to slide well onto the floor of either ravine. It is likely that many slopes slid last night but there is plenty of snow remaining in the alpine fetch zone to continue building large and dangerous wind slabs through the day today. 2-4” more inches of snow this morning will only add to the avalanche problem.

WEATHER: Though a slightly more easterly storm track downgraded our snowpocalypse to a healthy snowstorm, we did receive 14” of new snow at Hermit Lake and Harvard Cabin snow study plots. Snow showers will continue today with 2-4” more snow this morning. Wind is currently from the west at around 80 mph with gusts to 110 mph and the air temperature is 9F. Wind will decrease slightly through the day to the 65-85 mph range before increasing again after dark. Expect the westerly wind direction to continue transporting snow into east facing terrain, and cross-loading other aspects, reducing visibility in the process.

SNOWPACK: If you are looking for clues to alert you to possible avalanche danger today, consider heavy snowfall in the past 18 hours, increasing wind speed and continued snow fall. Also consider the wind slabs on the Tuckerman Ravine trail. You’ll notice cracking underfoot as you posthole up any trail today as cracks propagate through the layers of wind slab. Lots of small, low consequence test slopes exist in the woods and along the trail to study. You will find medium hard to firm wind slabs built by strong winds over soft, weak layers of snow deposited on calm winds yesterday afternoon which are somewhat representative of conditions elsewhere in our avalanche terrain. Above treeline and in the Ravines, low visibility due to fog and blowing snow will challenge your navigational skills along with your ability to assess your position relative to avalanche runout zones. Though it is likely that we passed the peak period of natural avalanche activity last night, the high winds speeds that we are experiencing tend to continue loading our slopes and building more wind slabs. Later today and tonight, as winds again increase, anticipate scouring in some terrain, possibly down to the old icy crust in some areas, such as in the northern gullies of Huntington Ravine. Today is a good day to stick to below treeline ski terrain or go ice climbing at lower elevations outside of steep gullies.

The Lion Head Winter Route is open and the most direct route to the summit. The Tuckerman Ravine Trail bridge is completed enough to allow traffic again. Please be careful of construction debris near crossover 7 on the Sherburne Trail and watch out for machine traffic on the Tucks and Sherburne Trail today. You may have noticed a new messaging product that MWAC is using to communicate our avalanche safety message. While new for us, the NWS Avalanche Watch and Warning system has been in use at other centers for a while now. With this system, we hope to reach a wider audience of backcountry travelers and possibly forewarn those who aren’t aware of the risk of avalanches. The NWS products are meant to supplement not replace the avalanche advisory found here daily through the season.

Please Remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
  • Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
  • For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.
  • Posted 7:45 a.m., Friday, December 30, 2016. A new advisory will be issued tomorrow.

Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2716

2016-12-30

Avalanche Advisory for Thursday, December 29, 2016

This advisory expires at Midnight tonight.

Huntington Ravine and Tuckerman Ravine avalanche danger will increase from LOW to CONSIDERABLE today. All forecast areas will have CONSIDERABLE avalanche danger. Natural avalanches will be possible and human-triggered avalanches likely. Careful snowpack evaluation, cautious route-finding and conservative decision-making are essential.

Avalanche danger will rapidly increase through the afternoon and evening hours. Travel in avalanche terrain near and after dark is not recommended.

AVALANCHE PROBLEM: Wind Slab and Storm Slab will compete for the primary avalanche hazard position today. Snow will increase in intensity in the afternoon, increasing our avalanche hazard from the current Low rating towards Considerable as natural avalanches become possible and human-triggered avalanches become more likely. By evening and overnight, large or widespread natural avalanches will become likely as snowfall rates increase. Safe travel today will be all about timing and keeping an eye on rates of snowfall, ridgetop winds, and other people above you acting as triggers. A hard, icy bed surface will make self-arrest and escape from even a small avalanche very difficult.

 WEATHER: Though the MWObs summit forecast today is for calm E and NE winds in the 10 mph range, NWS predicts higher wind speeds at 30-40 mph from the SE. Model suites bear out the NWS forecast more closely as do the current summit wind speed and direction from the S at 33 mph. Either of these forecast wind directions and speeds will create cross-loading conditions to some degree in the lee aspects of a predominately easterly wind direction today. Anticipate visibility to deteriorate rapidly as summit fog and snow descend. The temperature will increase into the high teens in the afternoon. This warming will contribute to the unstable situation by increasing the density of new snow. Wind and snowfall rates will intensify this evening and overnight with large or widespread natural avalanches occurring.

SNOWPACK: Our terrain is dominated by a wind scoured knife hard, icy melt-freeze crust with some pockets of pooled rimed crystals and graupel rounds resting on surprisingly steep benches. History has shown that new snow will bond on this type of crust, at least initially. If we receive the forecast 3-6” of snow today on relatively light easterly wind, it is quite likely that we will not see any natural avalanche activity during daylight hours. That said, I would expect quite a bit of spindrift or dry-loose avalanches on ice climbs due to low temperatures and a strong likelihood of dry light snow at the start of the storm. The small dry-loose avalanches will build the slabs we typically see beneath very steep (55 degrees or more) terrain such as the first pitch of Pinnacle and mid-slope Center Bowl. Lots of challenging weather with what is looking like a snowmageddon situation. Threading the needle today to play safely in the mountains may be possible but the margin for error is extremely slim. Expect avalanche danger to continue to increase tonight and through tomorrow as west winds ramp up and load the expected 20-30” of snow into east facing terrain.

The Lion Head Winter Route is open and the most direct route to the summit. The Tuckerman Ravine Trail bridge is completed enough to allow traffic again so you can avoid the detour. Please be careful of construction debris near crossover 7 on the Sherburne Trail and watch out for machine traffic on the Tucks and Sherburne Trail 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 the Harvard Cabin.
  • Posted 8:15 a.m., Thursday, December 29, 2016. A new advisory will be issued tomorrow.

Frank Carus, Snow Rangers
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2716

2016-12-29

Avalanche Advisory for Wednesday, December, 28, 2016

This advisory expires at midnight.

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

AVALANCHE PROBLEM: The avalanche problem today will be developing Wind Slab. This morning, these are almost nonexistent. Depending on what snow falls today, we may see these wind slabs grow in size, but expect them to remain isolated and easy to avoid by staying on the melt-freeze crust that formed during yesterday’s warm spell. The potential for long, sliding falls will be more of a threat throughout the day. Crampons and an ice axe will be crucial to safe travel.

WEATHER: Monday night and Tuesday brought warm temperatures and rain to the mountain. Yesterday, temperatures steadily declined ending the day with a trace of new snow. West and NW winds today in the 45-60mph range will decrease slightly.  We may see up to 2” of new snow today from lingering moisture. The big story is the upcoming 48 hours and the developing Nor’easter. Several models are calling for 24” along with strong winds.

SNOWPACK: Our snowpack hit the reset button yesterday. A ¼” of water percolated into the snow. This fell lightly and over an extended period of time, allowing the snowpack time to adjust to a new load.  Yesterday’s drop in temperature created a very firm snow surface.  Keep in mind that this firm potentially slick surface will become a bed surface after Thursday’s storm.  Light snow today will form small pockets under terrain features, but these will be easy to identify when compared to the dirty old surface.

The Lion Head Winter Route is open and the most direct route to the summit from the east side of the mountain. The bridge that is still under construction on Tuckerman Ravine Trail now allows traffic making this the preferred hiking route to gain elevation from Pinkham. Please be careful of construction debris near the top crossover when descending the Sherburne Trail and be on the lookout for heavy equipment as work continues.

Please Remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
  • Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
  • For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.
  • Posted 8:00 a.m., Wednesday, December 28, 2016. A new advisory will be issued tomorrow.

Helon Hoffer, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2716

2016-12-28

Avalanche Advisory for Tuesday, December 27, 2016

This advisory expires at midnight.

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

AVALANCHE PROBLEM: This morning, the avalanche problem will be Wet Slabs. The primary areas of concern would be the wind slab that formed in lee areas and under terrain features over the past weekend as these transition to wet slabs. Notoriously hard to predict, water may percolate lower into the snowpack and lubricate a layer farther down in the snowpack. Peak instability for wet slabs may already have passed as rain is no longer falling and temperatures begin their descent. As the snowpack freezes, beware of the potential for long, sliding falls. We may receive up to 2” of snow as the day progresses. Wind Slabs will develop, although depending on what time they form, they may bond well to the freezing snowpack.

WEATHER: Around dark last night, temperatures jumped to above freezing. Throughout the night, light rain, freezing rain, and ice pellets fell, delivering 0.26” of water. Today, strong W shifting NW winds have already reached the century mark and will linger there before decreasing to t the 70mph range by nightfall. With temperatures dropping today, and moisture lingering from the passing low pressure system, we may see up to 2” of upslope snow today and another 2” tonight.

SNOWPACK: Seven inches of snow fell since the previous melt/freeze cycle on December 17th and 18th. Strong winds over the past week scoured much of the terrain and left firm, well-bonded wind slabs in other areas. These wind slabs were not reactive in tests; they produced Q3 shears and did not propagate during ECTs. Rain last night soaked these slabs and old surface. As the temperatures drop, be on the lookout for hard icy surfaces to abound. Upslope snow showers will arrive later today on prime loading wind speeds, but I expect this snow to bond well to a simultaneously freezing surface. That being said, if we see the upper end of 4” today and tonight, beware of wind slabs forming quickly and be prepared to evaluate terrain with care if on the mountain early tomorrow.

The Lion Head Winter Route is open and the most direct route to the summit from the east side of the mountain. The bridge that is still under construction on Tuckerman Ravine Trail now allows traffic making this the preferred hiking route to gain elevation from Pinkham. Please be careful of construction debris near the top crossover when descending the Sherburne Trail and be on the lookout for heavy equipment as work continues.

Please Remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
  • Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
  • For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.
  • Posted 8:15 a.m., Monday, December 26, 2016. A new advisory will be issued tomorrow.

Helon Hoffer, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2716

2016-12-27

Avalanche Advisory for Monday, December 26, 2016

This advisory expires at Midnight tonight.

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

All forecast areas in Tuckerman Ravine have LOW avalanche danger. Natural and human-triggered avalanches are unlikely. The exceptions are Lobster Claw, Lower Snowfields and Little Headwall which are not rated due to a lack of snow.

Watch for unstable snow on isolated terrain features in both Ravines. Low danger does not mean no danger.

AVALANCHE PROBLEM: Stubborn wind slab will be the avalanche problem to concern yourself with today. High west winds the past two days repeatedly moved snow around in the terrain, scouring many areas and redepositing snow in others. In general, the snow took a beating as you would expect with gusts to 100 mph. Pockets of smooth but firm wind slab that escaped this pounding should hold your attention in the steepest terrain. While stubborn, these wind slabs could be triggered if loaded in the right spot. Assess and avoid large smooth pillows of snow whenever possible.

WEATHER: A scant .5” of snow fell early yesterday morning but otherwise no new snow was recorded in the past 24 hours. Sustained WNW winds in the 75-90 mph range on Christmas Eve moderated by mid-day yesterday. This morning the wind has died completely at lower elevations with 20 mph west winds on the summit. Winds will increase today to 50-70 mph by nightfall as low pressure moves in. Precipitation will start out as freezing rain after dark followed by rain before turning back to snow by morning.

SNOWPACK: Our snowpack has grown more slowly in the past week than it did earlier in the month when four distinct and widespread avalanche cycle quickly filled in our avalanche paths with debris. The majority of the 67” of snow recorded so far this December fell during the first half of the month. Since that time we received one rain event followed by small amounts of snow that built the stiff wind slabs that currently pepper our terrain. These upper wind slabs, while generally discontinuous and not exceptionally weak, should hold your attention in the steepest terrain. Plenty of old surface is still providing safe travel options that should allow you to avoid suspected unstable areas. The refrozen crust that dominates is hard enough to warrant crampons as terrain steepens but is breakable over faceted snow off trail and in the bushes so expect post-holing conditions in less frequently travelled terrain. Steep terrain is generally very firm and as such will resist efforts at self-arrest.

The Lion Head Winter Route is open and the most direct route to the summit. The Tuckerman Ravine Trail bridge is completed enough to allow traffic again so you can avoid the detour. Please be careful of construction debris near crossover 7 on the Sherburne Trail and watch out for machine traffic since the Tuckerman Ravine Trail is still not really passable for snow machines. Thanks for your continued patience!

Please Remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
  • Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
  • For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.
  • Posted 8:20 a.m., Monday, December 26, 2016. A new advisory will be issued tomorrow.

Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2716

2016-12-26

Avalanche Advisory for Sunday, December 25, 2016

This advisory expires at Midnight tonight.

Huntington Ravine has MODERATE and LOW avalanche danger. Central, Pinnacle, Odell and South have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. North, Damnation, Yale, and Escape Hatch have Low avalanche danger, Natural and human-triggered avalanches are unlikely. Evaluate snow and terrain features carefully.

Tuckerman Ravine has MODERATE and LOW avalanche danger. Sluice, The Lip, Center Bowl, Chute, Left Gully and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Right Gully has Low avalanche danger. Natural and human-triggered avalanches are unlikely. Lobster Claw, Lower Snowfields and Little Headwall are not rated due to a lack of snow.

AVALANCHE PROBLEM: In the past 24 hours, 2.3” of new snow fell with increasing wind speeds that created wind slabs in our forecast areas. Most of this snow fell in the morning through mid-day hours yesterday and was followed by strong WNW winds which loaded this snow into lee areas. These wind slabs are generally stiff and strong and therefore stubborn but weaker layers exist above the old icy crust. The greatest concern for a human-triggered avalanche is in the Lip and Center Bowl area of Tuckerman Ravine and in Central Gully in Huntington. Smaller but still potentially consequential pockets exist in many other areas so travel carefully and protect yourself before climbing into these pockets or avoid them altogether by staying on the old crust.

WEATHER: Temperatures in the teen’s this morning will fall further into the single digits as winds ramp up into the 70-90 mph range this afternoon. Wind will shift from west to north with gusts to 115 mph possible on the summit. Snow continues to be blown around as scouring and wind-packing of snow particles continues. Today would be good day to try out the new googles and balaclava Santa brought you, though staying home and roasting chestnuts by an open fire sounds even better.

SNOWPACK: Wind slabs which developed Thursday and Friday were unreactive Friday. Warm temperatures (38F at Hermit Lake) yesterday morning helped snow to settle further. The surface wind slab built yesterday was variable in thickness and tough enough to resist sustaining a crack for any great distance. That said, a weak layer of rimed snow from Friday created planar shears yesterday afternoon. The fact that the wind slabs are widely scattered through disconnected slopes is keeping our avalanche danger down. Plenty of old surface is still providing safe travel options to avoid suspect areas. This refrozen crust is hard enough to warrant crampons as terrain steepens but is breakable over faceted snow off trail so expect post-holing conditions in less frequently travelled terrain.

The Lion Head Winter Route is open and the most direct route to the summit. The Tuckerman Ravine Trail bridge is completed enough to allow traffic again so you can avoid the detour. Please be careful of construction debris near crossover 7 on the Sherburne Trail and watch out for machine traffic since the Tuckerman Ravine trail is still not really passable for snow machines. Thanks for your continued patience!

Please Remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
  • Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
  • For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.
  • Posted 7:55 a.m., Sunday, December 25, 2016. A new advisory will be issued tomorrow.

Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2716

2016-12-25

Avalanche Advisory for Saturday, December 24, 2016

Huntington Ravine has MODERATE avalanche danger. All forecast areas have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Evaluate snow and terrain features carefully to identify features of concern.

 Tuckerman Ravine has MODERATE and LOW avalanche danger. Sluice, The Lip, Center Bowl, Chute, Left Gully and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Right Gully has Low avalanche danger. Natural and human-triggered avalanches are unlikely. Lobster Claw, Lower Snowfields and the Little Headwall are not rated due to a lack of snow.

AVALANCHE PROBLEM: 1-3” of new snow today with increasing wind speeds will create wind slabs in our forecast areas. The size of these wind slabs will depend on the total snow received. If the upper end of the forecast amount falls, expect some medium sized human-triggered avalanches to be possible in areas like the Lip, under the ice in Center Bowl and above the choke in Chute and in good sized portions of Central Gully. If we receive 3” of new snow, anticipate natural avalanches becoming more possible than unlikely later in the afternoon and evening as winds ramp up into the 60-80 mph range. There is a possibility that our forecast elevations will receive some of this precipitation as rain, but it is unlikely that enough rain will fall to create a wet slab problem.

WEATHER: Though the summit weather forecast is calling for snow today, current temperatures lower on the mountain have us crossing our fingers that temperatures will cool sooner than hourly forecasts currently indicate. Temperatures on the mountain continue to rise this morning and are approaching 40F at Hermit Lake. Light snow shower activity should begin in the morning and continue during daylight hours as a weak low passes. Temperatures will drop later in the afternoon with winds increasing to the 60-80 mph range.

SNOWPACK: Wind slabs which developed Thursday and Friday were unreactive yesterday.  Warm temperatures (38F at Hermit Lake) this morning are helping this layer to settle further. Stability tests also revealed that snow was bonded pretty well to the old melt/freeze crust with density changes in the snow serving as the weak layer. The surface skin of wind slab was variable in thickness and tough enough to resist sustaining a crack for any distance. These wind slabs were widely scattered thorough the terrain with lots of old surface providing safe travel options for avoiding suspect areas. Given today’s wind speeds and snow fall totals, expect a similar picture today and tomorrow, though visibility will be challenging as clouds descend and blowing snow flattens light. The refrozen crust is hard enough to warrant crampons as terrain steepens but is breakable off trail so expect post-holing in less travelled terrain.

The Lion Head Winter Route is open and the most direct route to the summit. The Tuckerman Ravine Trail bridge is completed enough to allow traffic again so you can avoid the detour. Please be careful of construction debris near crossover 7 on the Sherburne Trail and watch out for machine traffic since the Tuckerman Ravine trail is still not really passable for snow machines. Thanks for your continued patience!

Please Remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
  • Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
  • For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.
  • Posted 7:45 a.m., Saturday, December 24, 2016. A new advisory will be issued tomorrow.

Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2716

2016-12-24

Avalanche Advisory for Friday, December 23, 2016

Huntington Ravine has MODERATE avalanche danger. All forecast areas have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Evaluate snow and terrain features carefully to identify features of concern.

 Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. Sluice, The Lip, Center Bowl, and Chute have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Lobster Claw, Right Gully, Left Gully and Hillmans Highway have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Lower Snowfields and Little Headwall are not rated due to a lack of snow.

AVALANCHE PROBLEM: Wind speed and direction today are favorable for building wind slabs as wind accesses recent snow in the alpine fetch zone. Our danger rating today straddles the line between Moderate and Considerable ratings due to a combination of factors. Though the likelihood of natural avalanches is bordering on unlikely in our Considerable rated terrain, I wouldn’t assume that a natural could not happen based on increasing wind speeds. Human-triggered avalanches are certainly possible in lots of our terrain so travel carefully, protect yourself when entering deeper or hollow sounding snow on climbs in Huntington. If skiing in Tuckerman’s, consider the icy bed surface and high consequence, early season terrain with lots of boulders, small cliffs and trees in your path. Careful assessment of new wind slab will be crucial for safe travel today.

WEATHER: The summit recorded around 3” of new snow in the past 24 hours with totals diminishing rapidly as you descend in elevation to around an inch at Pinkham Notch. Winds began yesterday morning on the lighter side (35-45 mph) from the SW then shifted west and slackened for a few hours. Light snow showers continued through the night as winds increased to the 50-60 mph range from the WNW. Wind today will shift slightly to the west at 50-70 mph with gusts to 80 mph and summit temperatures in the upper teens.

SNOWPACK: Low wind speeds during the early and heaviest period of snowfall yesterday sits on top of an icy melt/freeze crust from the rain on December 18th. This fast sliding surface will make self-arresting extremely difficult whether caused by a slip and fall or even a small avalanche sweeping you off your feet. Variable wind speeds and direction over the past 24 hours have built wind slabs which should be clearly identifiable even from a distance today as visibility improves. Wind slabs will grow in density today and may exist over a weaker layer of softer snow deposited during yesterday relatively low wind speeds. We will try to post pictures today if visibility improves as forecast.

The Lion Head Winter Route is open and the most direct route to the summit. The Tuckerman Ravine Trail bridge is completed enough to allow traffic again so you can avoid the detour. Please be careful of construction debris near crossover 7 on the Sherburne Trail and watch out for machine traffic since the Tuckerman Ravine trail is still not really passable for snow machines. Thanks for your continued patience!

Please Remember:

  • Safe travel in avalanche terrain requires training and experience. This advisory is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
  • Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast.
  • For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.
  • Posted 7:50 a.m., Friday, December 23, 2016. A new advisory will be issued tomorrow.

Frank Carus, Snow Ranger
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2716

2016-12-23