Avalanche Advisory for Thursday, March 31th, 2016.

This advisory expires tonight at 12:00 midnight.

Tuckerman and Huntington Ravines will have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely.  Dangerous avalanche conditions will exist.

AVALANCHE PROBLEM: The Wind Slab avalanche problem discussed yesterday will begin as the first issue today.  A rising temperature and rain showers will increase the potential for Wet Slab problems later this afternoon acting as the secondary problem.  Although coming second in timing it will be the first problem regarding hazard and is the main factor for the Considerable rating today.  Based on the current expectations of weather, the greatest potential for natural wet slab avalanches will be as we move through the late afternoon and into darkness when rainfall is expected to increase.  However, pay attention to warming and rain earlier in the day.  Warm air temperatures and rain on cold wind slab is a definite red flag requiring very careful terrain management to negotiate natural wet slab issues.

WEATHER: Temperatures are climbing quickly and the mid elevations are already deep into the 40’sF!  The 4000 foot level is already at almost 46F, with typical avalanche start zones hovering between 40-42F.  Rain is forecasted to work into our terrain in the afternoon and then pick up in potential around dinner time.  Periods of heavy rain are anticipated overnight with some thundershowers.  Very high winds are associated with this precipitation event, gusting over 100mph very late today.  Rain and high winds will continue tomorrow on the summits making for a very unpleasant day for alpine travel.

SNOWPACK:  The danger ratings for today are related to the near surface cold hard slabs that developed early Tuesday becoming warm and wet.  The rapid temperature increase and eventual rain will effect these areas of wind slab, causing the potential for natural avalanches to rise.  We have very little concern for the hard frozen snowpack that is below these recent wind slabs from 48 hours ago as they stabilized through earlier rain and several melt freeze cycles.   The new slabs we are concerned about today are not spatially widespread and several forecast area ratings are a bit conservative based on limited knowledge of new slab coverage.  We will be going through another “reset button” hit over the next 24 hours with about 0.5-.75″ of rain on our snowpack.  When we say “reset” it refers to an event that dramatically reduces or eliminates instability concerns in the current snowpack. However, until we make it through this rain event we must endure a spike in snow instability which we will see over the next 24 hours.  Having a conservative approach in these kind of weather conditions is important when considering to travel in avalanche terrain.  I would avoid the runouts under areas of recent slabs, likely being a brighter white than the older grey surface.

Other spring hazards that are significant threats today:   

  • Crevasses, moats and waterfall holes – Water flowing under the snow pack creates holes and thin spots in surface snow that are deep enough to injure or ….worse.
  • Falling Ice. Lunch Rocks and the floor are in the bullseye. Lunch Rocks, or “ICEFALL ROCKS”, gets hammered by ice every season it is not a good place to hang out. This location for many serious injuries over the years.

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 7:35 a.m., Thursday, March 31, 2016. A new advisory will be issued tomorrow.

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

2016-03-31

Avalanche Advisory for Wednesday, March 30th, 2016.

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has 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 to identify these features of concern.

Huntington Ravine has Low avalanche danger. Natural and human triggered avalanches are unlikely.

AVALANCHE PROBLEM: Hard Wind Slab is the avalanche problem today.  A period of snow, resulting in modest accumulations, ended about 28 hours ago culminating in very high winds gusting over 130mph (+208kph).  You can expect most areas to be scoured of new snow resulting in a patchwork of hard slab that survived in the strongest lee areas of W and WNW winds. Anticipate variable surfaces and stability based on your location.  Expect the easiest trigger point of hard slab to be on the outside edges where the depth is typically thinnest as well as shallow mid-slope spots that can be very hard to identify. Worldwide, these locations are classic triggering spots that users miss in their evaluations when skiing and riding.

WEATHER: On Monday the mountain received over 3/4″ of rain followed by 3.8″ of snow, which ended very early yesterday morning.  Winds raged between 90-133 mph for about 10 hours during the tail end of precipitation and in the hours following. Winds dropped through Tuesday, but blowing snow continued until the supply was exhausted after dark, even though winds remained over hurricane force.  Over the past 12 hours winds have fallen with high visibility from alpine terrain reaching 130 miles out.  Today, skies will be mostly clear with some building clouds, foreshadowing the approaching rain during the overnight, as spring temperatures and conditions return once again.  The mercury with climb today and eventually make it over the freezing point tonight, climbing to about 40F on the summits tomorrow, with….yup…. rain.

SNOWPACK: The quality soaking we received on Monday, with over 0.75″ of rain on the summit of Washington, gave us yet another factor to stabilize the mountain snowpack. We had a number of concerns prior to last weekend that were eventually reduced by Friday’s rain, warm conditions and skier compaction over the weekend, followed by more rain on Monday.  This stabilized the snowpack prior to new concerns that developed from the 3.8″ of snow falling from Monday night into very early Tuesday morning.  Currently, snowpack concerns remain solely from this new snow and not beneath the refrozen layers created by the warm up and rain from Friday to Monday.  Although limited in spatial distribution, assure you approach new slab with some respect and caution.  Skiers and riders may be tempted to seek out new snow but do so with conservative skepticism. These locales will most likely exist in the most protected areas below terrain features.  Examples include the roll over stretching from the Lip, through the left headwall, and including the Chute as you look up towards the south side of the ravine.  Besides avalanches, other spring hazards will come and go based on temperature and daily issues.  I would expect long sliding falls to be one of the main issues today with an increased threat of falling ice tomorrow with warm rain. These are the main factors to consider that historically have caused some tragic outcomes:    

  • Crevasses, moats and waterfall holes – Water flowing under the snow pack creates holes and thin spots in surface snow that are deep enough to injure or ….worse.
  • Long sliding falls are a significant threat today.Crampons, not Microspikes, are needed in most steep terrain. Arresting a fall on an icy steep slopes is practically impossible.
  • Falling Ice. Lunch Rocks and the floor are in the bullseye. Lunch Rocks, or “ICEFALL ROCKS”, gets hammered by ice every season it is not a good place to hang out. This location for many serious injuries over the years.

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., Wednesday, March 30, 2016. A new advisory will be issued tomorrow.

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

2016-03-30

Avalanche Advisory for Tuesday, March 29, 2016

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Considerable and Moderate avalanche danger. The Sluice, Lip, Center Bowl, and Chute have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. All other areas have Moderate avalanche danger.

All forecast areas of Huntington Ravine have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible.

AVALANCHE PROBLEM: Wind slab is the avalanche problem today. Hard wind slab may be building today in many areas due to very strong winds and overnight snowfall. The greatest concerns are in strongly sheltered lee areas which are rated Considerable today. Hard slabs are generally very strong, very dense, and run long distances when they release. This shifts the focus from human-triggering to natural avalanches. Venturing into the lower reaches of either ravine may put you within reach of a naturally-triggered slide.

WEATHER: Yesterday the mountain was subjected to yet another March rain, the fourth time this month. Precipitation transitioned to snow in the early evening, and snow continued to fall until the predawn hours, bringing 3.5″ of snow to the summit by the 7:50 a.m. measurement. W and WNW winds rose steadily during the snowfall, peaking at well over 100mph early this morning. Currently, we are experiencing what is likely the strongest winds we’ll see, as they are forecast to gradually decline throughout the day. By nightfall, summit winds should still be strong at 60-80mph. Upslope snow showers can be expected this morning, adding a little more to the totals before the air mass completely dries out. Blowing snow should be expected throughout the day.

SNOWPACK: With yesterday’s rain and overnight freezing temperatures, the underlying snowpack has stabilized to the point where today’s concerns are strongly focused on any slabs building at the surface. Winds gusting 110-130mph this morning lead us to suspect that none of the new snow is sticking in many of the forecast areas. This is most likely to be true in most of Huntington as well as Left Gully and Hillman’s Highway. However, as winds decrease today to speeds where snow can actually stick to the slopes, new slabs may develop if there is still a sufficient supply of snow in the alpine zone for loading to continue. The areas rated Considerable also may have been scoured or pounded into submission by the winds, but given their sheltered nature and being more protected from the winds, they are more likely to have developed deeper hard slabs. If this scenario is playing out, you will find strong hard snow that might have great stability relative to the impacts a person can generate, but the increasing weight of the slab caused by ongoing loading may be enough to trigger a spontaneous natural avalanche. This is the primary concern today, and it’s possible that it’s not actually a problem, but until we can get eyes and hands on the snow, making conservative decision is prudent.

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 8:10 a.m., Tuesday, March 29, 2016. A new advisory will be issued tomorrow.

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

2016-03-29

Avalanche Advisory for Monday, March 28, 2016

All forecast areas of Tuckerman and Huntington Ravines have LOW avalanche danger. Natural and human-triggered avalanches are unlikely. Lobster Claw, the Lower Snowfields, and Little Headwall are not posted due to a lack of snow in these areas.

AVALANCHE PROBLEM: A remote threat of Wet Slab avalanches is the primary concern later this morning due to rain further saturating our snowpack or waterfalls spilling out of their channels and into the snow. Our snowpack warmed and settled quite a bit over the past few days, but heavy rain could lead to a waterfall blowout or a deeper wet slab on an ice crust. Sluice through Chute in Tuckerman Ravine, along with the floor of the Ravine would be a good place to not linger today despite the low likelihood of a wet slab. Depending on how soon precipitation changes over to snow, some wind slabs may develop in the late afternoon.

Ice fall hazard, undermined snow and widening crevasses emerged as more significant threats particularly in the Lip area. Heavy rain today will again increase the risk of these potential threats. New snow can cover and hide crevasses and waterfall holes.

WEATHER: Rain will begin to fall mid to late-morning as a Low pressure passes through the area while temperatures remain above freezing. Rainfall is likely to be heavy at times before changing over to frozen precipitation types. Temps will drop through the day as cold air nudges in beneath warm upper level air. A period of freezing rain will result mid-day before a cold front becomes established over the mountains. Moderate southerly winds, in the 40 mph range on the summits, will ramp up and shift to the west later in the afternoon as snow develops. A combination of weather factors is in place for a solid upslope snowfall tonight and tomorrow on the heels of the cold frontal passage. High winds will develop through the night.

SNOWPACK: Warm daytime temperatures and sunny skies led to great corn skiing for folks over the weekend with even shady aspects softening yesterday. The prolonged warm temperatures and rain on Friday on our well settled snowpack reduced the concerns we had last week about deeper buried weak layers being players in our avalanche problems. Today’s weather will make it a worthwhile day to find something to do besides spending time in the mountains. Soaking heavy rain will make things pretty miserable though the day and freezing rain in the afternoon won’t make things much better. Trails in the area will return to their season default of wall-to-wall ice before some snow cover improves things though it is uncertain how low in elevation this will happen.

The Lion Head Winter Route is closed. Please use the Summer Lion Head Trail.

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., Monday, March 28, 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

2016-03-28

Avalanche Advisory for Sunday, March 27th, 2016

This advisory expires at Midnight.

Tuckerman and Huntington Ravines have LOW avalanche danger. Natural and human-triggered avalanches are unlikely.

AVALANCHE PROBLEM: Yesterday, we had some lingering wet slab and wet loose concerns in a couple of places with the expected warm up for Saturday. With another day for the snowpack to go through the melt freeze process, and lots of ski traffic compacting heavy slushy early corn in specific locations, this concern is even more remote today. The avalanche hazard today is taking a back seat to the other spring issues mentioned below.

WEATHER:  Today will start in the clear with increasing clouds filtering in, which should limit afternoon heating of the snowpack compared to yesterday.  Temperatures will rise to the mid 30’sF on the higher summits with winds from the S, shifting around to the W, and slowing increasing to 35mph.  For the prepared, it will be a nice day to be in the mountains.  Tonight, moisture will move into the region with rain expected all the way to the Washington summit on Monday.

SNOWPACK: Following Friday’s warm up, rain, natural avalanche activity in left Center Bowl, cold nights, and yesterday’s ski traffic, the snowpack has consolidated and stabilized. We have good confidence that we have made it through the vast majority of lingering stability concerns. There are a few locations that did not see ski traffic yesterday. These locales will be obvious with good visibility today. Keep the potential for a skier induced wet loose sluff in the back of your mind, albeit a remote possibility. Avalanche potential or the chance of minor waterfall blowout will rise tomorrow with rain, potentially heavy at times.  However, the snowpack should handle this water infiltration well if we stay to the forecasted water amounts in the Quantitative Precipitation Forecast (QPF).  The wet snowpack will then freeze again Monday night with 1-3” of snow to follow, perhaps creating some pockets of instability for Tuesday.

Other typical spring hazards include:         

  • Crevasses, moats and waterfall holes – Water flowing under the snow pack creates holes and thin spots in surface snow that are deep enough to injure or kill you.
  • Long sliding fallsare a significant threat today. Crampons are needed in most steep terrain. Microspikes are not adequate on anything steeper than a casual hiking trail. Arresting a fall on an icy steep slopes is practically impossible. Soft skiing conditions will be entirely dependent on direct solar exposure, low wind speeds and air temperatures rising above freezing.
  • Falling ice This hazard is reemerging as warm days return. Lunch Rocks and the floor remain in the bullseye. A better name for Lunch Rocks is “ICEFALL ROCKS” as it get hammered by ice every season it is not a good place to hang out and the location for many serious injuries over the years.

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 am, Sunday, March 27, 2016. A new advisory will be issued tomorrow.

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

2016-03-27

Avalanche Advisory for March 26, 2016

All areas of Tuckerman and Huntington Ravines have LOW avalanche danger. Natural and human-triggered avalanches are unlikely.

AVALANCHE PROBLEM: The snowpack is locked up by a variable density rain crust that developed overnight. A remote threat of a deep weak layers creating a wet slab avalanche exists but would take a big trigger like water flowing into a slab, icefall or lots of people on a slope like the Lip or Sluice. It is unlikely given today’s weather forecast that today’s warming will reach far enough into the snowpack to cause stability issues like wet loose larger than a pocket in most other areas.

Long sliding falls are a significant threat today. Crampons are needed in most steep terrain. Microspikes are not adequate on anything steeper than a casual hiking trail. Refrozen, icy snow surfaces from recent rain are spread throughout our terrain. Arresting a fall on an icy 30+ degree slope is practically impossible. Soft skiing conditions will be entirely dependent on direct solar exposure, low wind speeds and air temperatures rising above freezing.

WEATHER: Today’s weather forecast is looking good for surface snow conditions to soften a bit in the sun in areas like Right Gully through the Lip in the mid-day timeframe. Unfortunately, the weather forecast indicates a really good chance for the surface snow to refreeze in the afternoon due shadows cast by intermittent cloud cover, increasing winds from the east or simply by slopes passing into shade as the sun travels across it’s low, early spring path across the sky. Timing is critical today as is the ability to choose an alternative route should conditions be different than you were expecting.

SNOWPACK: New, thin wind slabs avalanched sometime during the rain event in the left side of Center Bowl. Deeper down, our snowpack contained weak layers of graupel and early facets which did not release during the .48” of rain yesterday. The upper meter of snowpack is variable with strong, refrozen pencil hard slabs along with much lower density snow that recrystallized during last night’s clear sky with cold temperatures. Strong spatial variability will create a variety of conditions for riding and climbing. It will be a good day to stay fully engaged by picking safer travel lines considering the fact that spring hazards are emerging with some lingering winter concerns.

Other typical spring hazards include:

Crevasses, moats and waterfall holes – Warm water flowing under the snow pack creates holes and thin spots in surface snow that are deep enough to injure or kill you.

 Falling ice – This hazard is reemerging as warm days return. Lunch Rocks and the floor remain in the bullseye. Reduce your hazard by reducing time spent in these fall lines.

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 8:45a.m., Saturday, March 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

2016-03-26 print friendly

 

Avalanche Advisory for Friday, March 25, 2016

All forecast areas of Tuckerman and Huntington Ravines will have CONSIDERABLE avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Lobster Claw, the Lower Snowfields, and Little Headwall are not posted due to a lack of snow in these areas.

AVALANCHE PROBLEM: The threat of Wet Slab avalanches is the main concern today. Warming temperatures will weaken existing slabs, many of them 2-3’ thick or more, while up to ½” of rain may overload them, potentially causing them to fail. The largest, most destructive avalanche activity would likely occur in Sluice through Chute, and Central Gully in Huntington. These are areas with the largest continuous wind slab with known weak layers beneath. Terrain like northern Huntington gullies, Odells and South could also spawn wet slabs and shouldn’t be underestimated.

WEATHER: Cold air dammed against the mountains and pooled in the valleys is creating conditions for a nasty glaze of ice to grow on surfaces. Meanwhile, mid-elevations on Mount Washington are above freezing and are expected to remain there for the next 12 hours or so for a total of 18-20 hours above freezing in our forecast areas. The warm front bringing today’s precipitation will be followed by a cold front with dry conditions. Temperatures will dip down below freezing in the early evening hours, improving snow stability in the process, but not before exposing our snowpack to warm temperatures and rain.

SNOWPACK: The old wind slabs, mentioned in the avalanche problem section above, have weak layers consisting of rimed particles and graupel with some early, developing near crust facets depending on aspect and thickness of overlying slab. These slabs can almost be called persistent slabs at this point due to their longevity. Our avalanche activity will likely peak today due to the rain and warmth on the slabs above these weak layers. It is conceivable that the settlement of the snowpack that began last night will reduce the threat of smaller avalanches in lighter density snow nearer the surface but I still consider wet loose avalanche if I was out this morning due to the heavy rain currently falling on the mountain. The real concern is the notoriously hard to predict wet slab activity today. Fortunately, our weather today is not the kind of weather that will drive people out into our terrain because human triggered avalanches in our snowpack today are likely.

Please use the Summer Lion Head Trail. The Sherburne Ski trail is closed ½ mile from the parking lot.

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 8:15a.m., Friday, March 25, 2016. A new advisory will be issued tomorrow.

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

2016-03-25 printer friendly

Today’s (Friday) Rain and the Weekend outlook

This is a quick post in prelude to the afternoon “Weekend Update” which we’ll post between 3 and 6pm. The weather maker moving through the area today will give us up to 0.45-.5″ of total melt water, primarily rain in the mountains.  Currently the valleys and the summits are colder than avalanche terrain at the mid elevations, which have been above freezing for many hours already. There is a chance for a period of heavy rain this morning with even a clap or two of thunder.  As this system moves through a cold front will usher in dry cold air.  The weekend should offer fairly clear skies, albeit a bit cool.  As for surface conditions and the existing cold snow that exists…..well…we need to wait a bit to see how much rain we get but generally we’re thinking this:

  1. Rain today will increase avalanche danger quickly with natural wet slab avalanche potential.
  2. The cold front, falling into the teens F on the summits, will begin locking up the snow pack from the surface down decreasing the avalanche danger, but creating slick surface conditions.
  3. Saturday morning will start cold with icy surfaces, but sun and and very light winds from the north will allow for softening on S and SE faces.
  4. The avalanche danger over the weekend will depend a lot on the amount of rain we get today, how deeply free water can percolate into the snowpack, and in part how much warming we get on Saturday and Sunday.  We will be in a general decreasing avalanche danger but we may have some aspects higher than others (Moderate and Low). Again depends on rain today and how hard a “reset button” our snow pack goes through.  See Today’s avalanche advisory discussing the Considerable rating for Friday, don’t forget to check the weekend update later today, and certainly the Saturday Avalanche advisory in the morning.  Chris

 

Avalanche Advisory for Thursday, March 24, 2016

This advisory expires tonight at 12:00 midnight.

Tuckerman and Huntington Ravines have Moderate avalanche danger.  Natural avalanches are unlikely and human-triggered avalanches are possible.  Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully to identify features of concern.

AVALANCHE PROBLEM: Wind slab is going to be the #1 problem again today.  Only about one inch of snow fell during the morning hours yesterday, but snow began again during the predawn hours on a light W wind. Continued snow this morning will taper to showers in the afternoon on a building wind.  Expect the avalanche danger to build through the day with new loading to accelerate as wind velocities increase late in the day.  New wind slab will load on a variety of snowpack instabilities that already exist in both Ravines, but primarily in Tuckerman. Many E facing slopes were rated Moderate yesterday so today’s weather event will push some areas to the upper ceiling of the definition, edging towards Considerable.  The Lip area of Tuckerman is in the bullseye to have natural avalanche potential first.

WEATHER: Snow this morning will taper to snow showers and fog this afternoon as temperatures warm from the current 16F up to the mid 20’sF by nightfall. Expect precipitation, up to 3″ (7.5cm), to increase in density slightly. Calm to light west winds this morning will increase and shift to the southwest ultimately blowing in the 40-55 mph (64-88kph) range. Expect reduced visibility through the day as precipitation is replaced by summit fog this afternoon due to incoming moist airmass.

SNOWPACK: As Jeff stated in yesterday’s advisory from his field work on Tuesday, spatial variability is the dominate personality of the Ravines right now. There are old icy surfaces, wind sculpted snow, and numerous density slabs as soft as 1 finger hard. Some of these slabs failed on several weak layers over crusts.  Some thin slabs near the surface, up to 30cm (12″) deep, failed upon isolation.  Although this was not the norm, compression test scores to CT8 produced concern.  Moving deeper, to around 75cm, stability increased, but with extended column scores between ECTP14 and 20 indicating a potential for crack propagation.

Today’s snowfall, between 1-3″ (2.5-7.5cm), will load on an increasing W wind, shifting from the SW.  Snow will load primarily on E and NE facing aspects in both Ravines.  The Lip, Centerbowl, Chute, Left Gully and Hillman’s will be most affected in Tuckerman while in Huntington, I would have most concern in Central, Pinnacle, Odell and South Gullies.  Showers will continue after dark with an additional 1-2″ expected overnight while winds increase from 60mph (96kph) late this afternoon towards 85mph (136kph) after midnight.  For today’s recreation activities expect avalanche likelihood and peak instability to come late in the day towards darkness.  Sometime during the overnight we will likely get beyond the highest probability window, into an increasing stability trend briefly before rising quickly tomorrow as rain is expected at all elevations.

The bottom line is E and NE facing slopes will move through the Moderate rating definition through the day, many being responsive to human triggers.  I have fair confidence that later today, as winds increase, a number of these will edge closer to a Considerable rating definition.  However, in most cases this reality should hold off until after dark.

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 8:15a.m., Thursday, March 24, 2016. A new advisory will be issued tomorrow.

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

2016-03-24

Avalanche Advisory for Wednesday, March 23, 2016

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Moderate and Low avalanche danger. The Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s 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. Watch for unstable snow in isolated terrain features.

Huntington Ravine Moderate and Low avalanche danger. Central Gully has Moderate avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. All other areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely. Watch for unstable snow in isolated terrain features.

AVALANCHE PROBLEM: Wind slab is going to be the #1 problem again today, although the amount of snow we get this morning will determine whether we are dealing with primarily older slabs or if we also have new slab problems developing today. The worst stability in either old or new slab rated at Moderate will be found in locations from Sluice through Chute in Tuckerman and Central in Huntington. Other areas rated with the same rating should be treated with caution as well, as you may find smaller areas of very touchy snow or larger expanses of more stubborn and difficult-to-trigger slab. Expect isolated pockets of instability in Low-rated areas such as Right Gully or much of Huntington. New snow will be increasing the overall avalanche hazard!

WEATHER: While the summit recorded 3.5” Monday night, lower elevations on the mountain weren’t so fortunate. We saw only 1” that morning at Hermit Lake and our field time in Tucks led us to believe that even Bigelow Lawn only saw a light snowfall. Last night, snow began around midnight on WSW winds which are diminishing gradually over time. For today, 1-2” of new snow is forecast. Temperatures around ravine elevations may flirt with heading above freezing, but with cloudy skies I don’t expect much in the way of heating.

SNOWPACK: As is often the case, spatial variability is quite strong right now. There are a mix of surfaces, including scratchy hard crust, e.g. in much of Right Gully; heavily wind-effected snow, e.g. up high above the steepest pitches of Chute and Center Bowl; and recently formed 1F+ (1 finger hardness) slab, which is found in pockets scattered throughout the ravines and larger sections of the Lip, Center Bowl, and Central Gully. Some locations also have sun crusts and/or melt-freeze crusts in the upper portions, e.g. in Sluice’s midsection. The most concerning situation is where smooth new wind slabs have built over the March 16 rain crust or over sun crusts on S-facing slopes. Weak snow sits just above the rain crust, with an overlying slab of variable thickness comprised of a couple weak interfaces. In one pit yesterday, the surface slab yielded CT0 and CT8 compression test scores in the upper 1 ft. of snowpack, while the entire slab failed at ECTP14 and ECTP21 above the rain crust. The most significant finding, which shouldn’t be much of a surprise, is that the snow was more stable in test locations with thicker, more wind-effected slab.

Today, new snow will be adding additional load above existing weak layers, making them more susceptible to human-triggered releases. If we get more than the forecasted 2” and winds stay strong, we may exceed the day’s hazard rating. In the large cone of windblown snow in the lower part of Chute, as well as under the headwall ice, in much of the Lip, and in the open midsection of Sluice are where this would be most likely. Don’t be lulled into complacency if your routes involve smaller snowfields. If an area has anything other than the hard icy crust, expect it to be unstable until you can determine otherwise.

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 8:15a.m., Wednesday, March 23, 2016. A new advisory will be issued tomorrow.

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

2016-03-23