Avalanche Advisory for Saturday, January 31, 2015

This advisory expires at midnight.

Very dangerous avalanche conditions exist in Tuckerman and Huntington Ravines. Travel in avalanche terrain, including low angle terrain in the floor of the Ravines, is not recommended.

Tuckerman Ravine has High, Considerable, and Moderate avalanche danger. Sluice, Lip, and Center Bowl have High avalanche danger. Natural avalanches are likely and human-triggered avalanches are very likely. Lobster Claw, Right Gully, Chute, Left Gully, and Hillman’s Highway have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Careful snowpack and weather evaluation, cautious route finding and conservative decision making are essential. Little Headwall and the Lower Snowfields have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanche are possible.

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

AVALANCHE PROBLEM: Wind slabs are the imminent threat today. New snow deposited on near calm winds yesterday will form a soft weak layer on which new wind slabs will form today. These slabs will continue to build through the day and could avalanche spontaneously from lee areas without a human to trigger them. Avalanche paths are developed to the point that avalanches will likely run out onto low angle and flat terrain therefore travel into the vicinity of the Fan in Huntington or into the floor of Tuckerman much beyond the Connection Rescue Cache is not recommended.

WEATHER: 5.5” (13.4cm) of new snow was observed on the 24 hour board this morning at the Hermit Lake snow plot. The summit recorded a similar figure that of 5% density snow which will be easily blown into our avalanche starting zones. It is a serious day to be in the mountains. High winds ramping up from 60ish mph to 75-95mph (121-153kph), gusting to 110mph (177kph), frigid temperatures around -5F (-21C), low visibility and elevated avalanche risk make it a very challenging day. I know I am only here so I won’t get fined.

SNOWPACK: Hopefully you are not thinking that areas rated Considerable are the better target for recreation today. Though the risk of natural avalanches in these areas is less than in areas rated High, you could still easily trigger a sizable avalanche. New snow over the past 24 hours has formed a sensitive weak layer with wind slabs on top that will be soft enough to trigger pretty easily. Today’s wind will ramp up and continue the process of creating denser slabs over a softer, weaker layer. Bear in mind too that there is still snow from the Tuesday event earlier in the week that will be available for transport due to the short period of time that high winds were able to effect it. Later today, wind velocities will increase to the point that snow deposited earlier during this storm cycle will begin to erode, especially in Huntington Ravine. Though the avalanche danger will diminish at that point, there many other factors that should make you consider your travel decisions very carefully.

The Lion Head Winter Route is open but will present a significant challenge today given the current weather conditions and forecast. A minor incident could turn into a life or death struggle.

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. January 31, 2015. 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

2015-01-31 print friendly

Avalanche Advisory for Friday, January 30, 2015

This advisory expires at midnight.

Tuckerman and Huntington Ravines have CONSIDERABLE avalanche danger.   Natural avalanches are possible and human-triggered avalanches are likely. Dangerous avalanche conditions will exist today. Careful snowpack and weather evaluation, cautious route-finding and conservative decision-making is essential.

AVALANCHE PROBLEM: Wind Slabs left over from the last storm coupled with the new Wind Slabs that are currently developing are the #1 problem today.  Up to +/-6″ (15cm) of new snow today will load new unstable slabs into the Ravines today.  Schizophrenic wind speeds and direction as well as a dropping temperature will create multiple density changes and snowpack layering effecting this problem.  Expect new windslab to develop on NE facing slopes first, then E, followed by SE facing aspects this afternoon.

WEATHER: Conflicting weather forecasts from a number of sources required a review of model outputs as well as phone calls to the Mount Washington Observatory staff to resolve conflicts in the wind direction forecast. The OBS staff’s latest model research indicates that wind will shift quickly from its current SW direction through the W before settling in to blow from the NW. This wind direction will more efficiently build dangerous wind slabs with the potential 6” (15cm) of snow during daylight hours than a shift through the E.  Some sources believe this counterclockwise E spin on the compass rose is possible, but we are most confident today with our local specialists. Winds are expected to diminish for a period mid-day before cranking up again. This creates the potential for a lighter layer of snow to build before higher winds create a slab on top.

SNOWPACK:  This morning we wrestled with a difficult weather scenario and expected wind directions.  These discrepancies relate directly to very different snowpack instabilities depending on what exactly plays out.  We have good confidence that winds will directly load new wind slabs across all our forecast areas as the flow moves from the SW, then W, and eventually from the NW.  This will initially load NE and E facing slopes such as start zones in Hillman’s, Left Gully and the Chute in Tuckerman as well as the Escape Hatch, South, and Odell gullies in Huntington. Expect direct loading of our most historically prolific avalanche producers this afternoon such as Tuckerman’s Center Bowl, Lip and Sluice along with Huntington’s Pinnacle, Central, and Yale.  New wind slab should layer into the terrain with various densities due to a dropping temperature and the up and down wind velocity over the next 12 hours.  If natural avalanches do occur they are most likely to fail on a weak layer of low density snow that develops during periods of light wind today, rather than directly on the interface with the old surface.  It is possible that avalanche activity may step down into left over windslab from the last storm.  Hard slab that was in place across most of the Tuckerman Center Bowl would likely propagate a long fracture leading to a more significant failure and avalanche.  This is quite plausible with the load of a natural, new, soft slab avalanche overrunning these older dense slabs today.  There is a lot of complexity to how things will exactly play out today which should force you to be conservative in your decision making.

We are now using the Winter Lion Head Route which is marked by orange signs half way up to Hermit Lake at the bottom and at treeline up top.  Expect a post holing slog until it is packed out, snowshoes could be helpful.   The Sherburne Ski Trail has improved dramatically. Based on so many variables for the weekend we will do an over all conditions “Pit” post today getting into the nasty weather, the Sherburne, the newly opened Lion Head winter route, and what Frank forecasts for his beloved Patriots on Sunday.

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 8:35 a.m. January 30, 2015. A new advisory will be issued tomorrow.

Christopher Joosen and Frank Carus, Snow Rangers
USDA Forest Service
White Mountain National Forest
(603) 466-2713 TTY (603) 466-2856

2015-01-30 print friendly

Avalanche Advisory for Thursday, January 29, 2015

This advisory expires at midnight.

Tuckerman Ravine has Moderate and Low avalanche danger.  The Lobster Claw, Right Gully, Sluice, Lip, Center Bowl, and the Chute have Moderate avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible.  Left gully, Hillman’s Highway, the Lower Snowfields, and the Little Headwall have Low avalanche danger.  Natural and human triggered avalanches are unlikely except in isolated terrain features.

Huntington Ravine has Moderate and Low avalanche danger.  North, Damnation, and Yale gullies have Moderate avalanche danger.  Natural avalanches are unlikely and human triggered avalanches are possible.  Central, Pinnacle, Odell, South, and Escape Hatch have Low avalanche danger.  Natural and human triggered avalanches are unlikely except in isolated terrain features.

AVALANCHE PROBLEM: Wind Slabs that developed from about a foot of snow from the recent storm are the #1 problem today.  Wind slabs formed initially on very high winds with an easterly component.  This created very hard slabs initially as the Ravines were on the windward side of early storm winds.  The second half of the Tuesday/Wednesday storm came in on a diminishing NE and N wind.  This loaded softer wind slabs on S facing aspects.  Expect wind slabs to be softer and easier to trigger on these S facing slopes and anticipate slabs facing directly E and N to be harder, more difficult to trigger, but resulting in larger avalanches if they fail.

WEATHER: Wind loading shut down yesterday afternoon as winds fell to 50 mph resulting in excellent visibility.  Today very low winds and sun will dominate the day until late when a shifting wind moves from the NW to the S and increase.   Late in the day gusts may move into the 60’s mph. (96kph).  This may cause some light new loading on N facing slopes.  New snow moving in tonight and all day tomorrow is expected to bring 4-8” of new snow causing an increase in avalanche danger for Friday and perhaps Saturday.

SNOWPACK: There are some slopes, facing towards the E, which lost snow due to wind gusts over 100mph (160kph) during the early parts of the storm. As winds subsided a bit and moved to the NE, NNE and then N, some of these slopes were cross-loaded and wind packed. Meanwhile, S facing slopes became heavily loaded with soft wind slab.  As some examples, you can expect soft slabs in the upper start zones of Huntington’s Damnation and Yale gullies as well as Tuckerman’s Lobster Claw, Right Gully and the Sluice.  These are considered as having Moderate danger and should be easier to trigger than the harder slabs facing E and N.  A number of these harder slopes such as the Center Bowl and the Chute also harbor Moderate danger, but will be more stubborn and difficult to trigger. However if they fail expect these harder slabs to propagate farther resulting in larger avalanches.  So areas posted as Moderate have some different issues within the same definition.  Both issues may result in dire consequences, but softer slabs will be a bit more straight forward to manage for avalanche skilled users than firmer wind hardened slopes.  I would be wary traveling out into the middle of a large hard slab so soon after this storm.  In areas posted at Low danger keep your eyes open for isolated snow instabilities such as the mid slope sections of Hillman’s and Left gully.

Late in the day a shifting, increasing, wind from the S may pick up some snow in alpine areas that have been protected by terrain features during the recent N wind.  Look for plumes late this afternoon as clues that some light loading on N facing slopes may be occurring.  Saying this, the probability this will cause new problems is remote, but worthy to note.  Expect snow tonight and all day tomorrow, adding up to 4-8” (10-20cm), to increase the avalanche danger into the beginning of the weekend.

We are now using the Winter Lion Head Route which is marked by orange signs half way up to Hermit Lake at the bottom and at treeline up top.  Expect a post holing slog until it is packed out, snowshoes could be helpful.   The Sherburne Ski Trail has improved dramatically.

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 8:45 a.m. January 29, 2015. A new advisory will be issued tomorrow.

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

2015-1-29

Avalanche Advisory for Wednesday, January 28, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has HIGH and CONSIDERABLE avalanche danger. Lobster Claw, Right Gully, the Sluice, Lip, Center Bowl, and Chute have High avalanche danger. Natural avalanches are likely and human triggered avalanches are very likely. Left Gully, Hillman’s Highway, and Lower Snowfields have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. The Little Headwall has Moderate danger. Natural avalanches are unlikely and human triggered avalanches are possible.

Huntington Ravine has HIGH and CONSIDERABLE avalanche danger. North, Damnation, Yale, Central, and Pinnacle have High avalanche danger. Natural avalanches are likely and human triggered avalanches are very likely. Odell, South, and Escape Hatch have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely.

Although the Winter Storm Warning has expired, avalanche conditions will remain very dangerous. Travel in avalanche terrain is not recommended.

AVALANCHE PROBLEM: Wind slab is the primary avalanche threat today. These will continue to develop as winds redistribute recently fallen snow into the forecast areas. S-facing slopes will be the areas of greatest concern, such as North and Damnation in Huntington and Lobster Claw, Right Gully, and Sluice in Tuckerman. Anticipate large avalanches reaching farther into the lower portions of the ravines, as well as avalanche runouts crisscrossing in flat ground well before you enter anything steep. You don’t need to be on a steep slope to be at risk today!

WEATHER: It looks like we’re in a good pattern right now, with two more storms possible in the short term.  Yesterday’s winter storm was a good one, even if we didn’t get the 2+ feet that coastal towns received. The snow plot at Hermit Lake had 9.5″ (24.5cm) of 5% density snow. Given the wind speeds and drifting that complicate snow collection and measurement at various locations, this is the amount that I’ll hang my hat on. Other measurements such as the summit and at Pinkham show ~10% density snow, but I can tell you that what fell yesterday was not that dense. At Hermit Lake the snow was relatively unaffected by wind at the measurement site. Strong NE winds blew during the event yesterday, gusting to 111mph (179kph) on the summit (hence the challenge with measuring snow!). Today they will be shifting the the N and remaining strong, which will continue to load snow into avalanche paths around the mountain.

SNOWPACK: Once again your attention should be focused on what’s going on at the surface rather than looking for deeply buried weak layers. Obviously, we weren’t about to go poking around the ravines at the height of the storm yesterday, so at this time we don’t have much direct information about what actually happened. This is the kind of day where we rely on a long history and experience forecasting for this mountain. Today we expect continued loading of S and E facing aspects. Although it is very likely that these slopes have already had some avalanche activity, it remains likely that there will be more avalanches today. As one runs on top of the other, they often go farther down the slope than previous slides, extending the reach of avalanche terrain. It’s a good day to be cautious about where or when you decide to turn around.

We will begin to switch over to the Lion Head Winter Route. All signs should be swapped out and the summer trail closed by later this morning. If you are on either of these trails today, pay attention as they both will bring you very close to, or even into, avalanche paths. This will be especially true in the flat section from the Lion Head to the base of the summit cone. The John Sherburne Ski Trail improved tremendously with this storm, but remember that there may be some wind-exposed sections of thick ice crust.

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. January 28, 2015. A new advisory will be issued tomorrow.

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

2015-01-28

Avalanche Advisory for Tuesday, January 27, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has HIGH and CONSIDERABLE avalanche danger. Lobster Claw, Right Gully, the Sluice, Lip, Center Bowl, and Chute have High avalanche danger. Natural avalanches are likely and human triggered avalanches are very likely. Left Gully, Hillman’s Highway, the Lower Snowfields, and Little Headwall have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely.

Huntington Ravine has HIGH and CONSIDERABLE avalanche danger. North, Damnation, Yale, Central, and Pinnacle have High avalanche danger. Natural avalanches are likely and human triggered avalanches are very likely. Odell, South, and Escape Hatch have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely.

A Winter Storm Warning is in effect today. Avalanche conditions will be very dangerous. Travel in avalanche terrain is not recommended.

AVALANCHE PROBLEM: Storm Slabs and Wind Slabs are going to be forming rapidly and with gusto as this storm intensifies and moves northward. The aspects that will receive the greatest loading face to the SW and S. In our terrain, these are the lookers’ right side of Tuckerman and the northern gullies of Huntington. I am confident that naturally-triggered avalanches will take place in these forecast areas, and I would not be surprised to see avalanches in steep S-facing terrain that is outside of our forecasted avalanche paths.

WEATHER: This storm is what was needed to distract the news world from football inflation scandals, at least in New England anyway. While impacts are expected to be very strong up and down the east coast, what we are expecting here is simply a good old fashioned Nor’easter. It’s not going to be a storm for the ages up on Mt. Washington, but it will be a good one. We are expecting total storm accumulations of 12-20” (30-50cm), which includes snow overnight and tomorrow. Today’s amounts will hopefully fall into the 8-12” (20-30cm) range. Winds are one of the more interesting components to this event. Strong NE winds will persist through daylight, then a gradual shift to the NNE and N after dark. This directly impacts where avalanche danger will be greatest, so please read on…

SNOWPACK: All eyes are on the top of the snowpack for stability problems today. Generally good stability preceded this event. As snow is blown in on NE winds, some aspects will be directly on the windward side of the mountain. These are the areas forecasted at Considerable danger. They will not see nearly as much wind loading as the slopes facing to the S and E, and in some past storms, strong easterly winds actually removing snow from windward slopes in the Cutler River Drainage. While there will be a lesser concern in windward locations, I still would not recommend traveling here today given possibility of naturally triggered avalanches and the crisscrossing of runout paths. Areas posted at High can be expected to avalanche multiple times during the event and will probably push the runout zones farther than they have yet gone this season. Going up to the bottom of Tuckerman or Huntington Ravine will put you at risk of serious injury or death at the hands of a naturally triggered avalanche. This is true even if you are just “going to check it out” or “going to take a look,” two phrases people often say to us we watch them hike up into avalanche terrain.

Winds shift further to the N and NNW tonight. With additional snow, this will keep the danger elevated. Another storm is scheduled for arrival on Friday. It’ll be a good week to read the advisories before heading into the mountains.

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 8:40 a.m. January 27, 2015. A new advisory will be issued tomorrow.

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

2015-01-27b

Avalanche Advisory for Monday, January 26, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Moderate and Low avalanche danger. Lobster Claw, Right Gully, the Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Left Gully, Hillman’s Highway, the Lower Snowfields, and Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely.

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

AVALANCHE PROBLEM: In Tuckerman Ravine, you’ll be dealing with large snowfields with thick wind slab as your avalanche problem today. Huntington is mostly scoured of new snow, with the exceptions of down near the approaches and lower sections of Central, Pinnacle, and Odell. In these areas you may find softer dry loose deposits mixed with wind slab. In Tuckerman, the slabs will have a lot of strength in many locations, but remember that you only need to find a hidden weak spot and you could easily trigger a sizeable avalanche.

WEATHER: It’s pretty hard to ignore the hyperbole around the “historic” winter storm that is poised “bury the Northeast from New Jersey to Maine.” This will begin tonight, but won’t be affecting today’s avalanche issues. Later today, I’ll take a look at this storm in more detail in The Pit on our website. But for today, you will want to know that Mt. Washington received just under 4” (10cm) of new snow in the past 3 days at the upper elevations. Down at Hermit Lake, we received less than half of this amount. Yesterday winds blew from the NW at 60-90mph throughout much of the day before diminishing overnight. Today begins with gorgeous calm, cold weather and clear skies…a perfectly cliché calm before the storm.

SNOWPACK: As mentioned, Huntington was mostly scoured of the new snow, leaving behind a lot of old surface including some old, gray crust in some spots. Areas at the base of Central, Pinnacle, and Odell have caught our eye as where you might find isolated pockets of unstable snow. Often strong winds carry snow lower down into the terrain and sluffing contributes to this as well. If you’re alert, you should be able to avoid or manage these issues without too much difficulty.

In Tuckerman Ravine, Hillman’s and Left Gully are also mostly scoured. The biggest issues in Tuckerman are found in locations strongly protected from NW winds, such as the Sluice and Lip. The crown line left behind from Tuesday’s avalanche in the Sluice and Lip has been fully reloaded. Looking farther left, the Center Bowl and Chute show lesser amounts of loading, but are not scoured as Left Gully is. Expect slabs in this area to be thick and reasonably strong, but to hold the potential for a large avalanche if they were to be triggered.

We continue to hear reports of just how bad the skiing is on the Sherburne. I drove down it yesterday and can confirm these reports to be true. Let’s hope there is enough snow to bury the current ice layer so deeply that it doesn’t reappear until May. The Lion Head Winter Route remains closed; use the summertime Lion Head Trail if going this way. Trees on the traverse section at treeline are still standing tall and proud, so we’ll see how the coming storm develops this avalanche path and reassess it later.

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. January 26, 2015. A new advisory will be issued tomorrow.

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

2015-01-26

Avalanche Advisory for Sunday, January 25, 2015

This advisory expires tonight at 12:00 midnight.

All forecast areas of Tuckerman Ravine and Huntington Ravine have CONSIDERABLE avalanche danger. Dangerous avalanche conditions exist. Natural avalanches are possible and human triggered avalanches are likely. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential. The only exception to this is the Little Headwall in Tuckerman which has Moderate danger. Natural avalanches are unlikely and human triggered avalanches are possible in this forecast area.

AVALANCHE PROBLEM: Wind slab will be developing today, causing avalanche danger to be on the rise in all forecast areas. Some locations will be directly loaded from blowing snow being deposited on strongly sheltered slopes. The areas of greatest concern include the Sluice, Lip, and Center Bowl in Tuckerman as well as Central and Pinnacle Gullies of Huntington. Other adjacent locations will also have new slab development, and although not quite as quickly, the avalanche danger will rise in these areas to the Considerable level.

WEATHER: Yesterday evening Mt. Washington picked up some more new snow totaling just less than 3” (7.5cm) by 6am. Additional snow will continue through this morning. When it’s all said and done, 4-6” of new snow will be available for 65-85mph (105-139kph) NW winds to pick up and deliver to the eastern-facing ravines. You can expect falling temperatures through today along with the possibility of clearing out of the fog later. Until then, visibility will be quite poor due to fog and blowing snow.

SNOWPACK: Your primary focus on the snowpack today should be on the upper layer of slab that is developing. Some deeper issues may be of interest to serious snow geeks, but from the recreational perspective you can keep your attention at the surface and in the air above. Winds at 65-85mph have the capacity to pick up and move snow that has fallen far away from the ravines. Even if this morning’s forecasted 2-4” comes in at the lower end, we expect all areas to be loaded to a point where we have concerns of naturally triggered avalanches. If we do get the upper end of forecasted snowfall, in some locations we might be moving from naturally triggered avalanches being “possible” toward “likely.” Ultimately, today you should know that there are concerns about stability today, particularly with regards to human triggered avalanches if people are out in the avalanche start zones.

If you’re expecting boot-deep powder on the Sherburne, you’ll have a disappointing day. There may be drifts where it’s gotten that deep, but from Hermit Lake down to Pinkham there is less new snow that up above treeline.

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. January 25, 2015. A new advisory will be issued tomorrow.

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

2015-01-25

Avalanche Advisory for Saturday, January 24, 2015

This advisory expire at midnight.

All forecast areas of Tuckerman Ravine and Huntington Ravine have MODERATE avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Evaluate snow, terrain and weather conditions carefully. Dangerous avalanche conditions may develop after dark and overnight!

AVALANCHE PROBLEM: Be thinking about Persistent Slabs scattered around in the Ravines as your primary avalanche hazard if you are planning to thread the weather needle today in the Ravines. This hazard earns a Low rating this morning. New snow on increasing winds beginning around noon will begin to create a Wind Slab hazard. The rate of new snowfall will determine the likelihood and size of the new, unstable wind slabs as well as how soon we reach the Moderate hazard rating. As the day progresses, the likelihood of natural and human-triggered avalanches will become increasingly possible, particularly in lee areas such as Central and Pinnacle Gully and where the Tuckerman Ravine trail enters Tuckerman Ravine (the Lip and Sluice forecast areas). We may reach a Considerable danger rating after dark.

WEATHER: Clouds will thicken and descend this afternoon as the storm system to our east brushes by the area. 1 to 3” (2.5 to7.5 cm) of new snowfall is forecast this afternoon and evening followed by 1-3” more snow overnight. NW winds will ramp up as the storm moves through, building unstable wind slabs in the process.  Temperatures will drop back towards 0F (-18C) tonight with strong winds complicating travel.

SNOWPACK: A generally hard, wind packed surface (P) in most areas is bridging over discontinuous areas of weak layers (4F-F) on some benches and in some lee areas which were not scoured out by avalanche activity last week end or Tuesday morning. Also, some pockets of softer slab that developed on Tuesday may remain in lee pockets. It is also worth remembering that the wet snow Sunday may be hiding some ice flows and may not be well bonded, at least in areas that did not already avalanche on Sunday. Skiers in Right Gully and Hillman’s the last couple of days have found the surface carvable but firm and worthy of crampons on the ascent. Overall, the snowpack is pretty thin with lots of ice still exposed in Center Bowl and around the Open Book. The recent avalanche activity in Huntington has covered more shrubs on the approach to Odell and the firm snow has made for good cramponing and easier approaches. Ice is still somewhat thin on Pinnacle Gully.

The Sherburne Ski trail is icy on the upper half due to the freezing rain last weekend. Lots of bumps and waterbars are still around. A “dust on crust” situation will develop as the afternoon wears on. We are running the snow cat on the Tuckerman Ravine trail to Hermit Lake and part way into Huntington to try to improve SAR access so please be aware that a large steel object may be descending in the middle of the trail this afternoon.

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 8:40 a.m. January 23, 2015. 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

2015-01-24

Avalanche Advisory for Friday, January 23, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman and Huntington Ravines have Low avalanche danger.   Natural and human-triggered avalanches are unlikely, but watch for unstable snow in isolated terrain features. It is important to realize these pockets do exist and can produce smaller avalanches in remote steep locations.  This is a greater concern in Tuckerman than in the wind scoured gullies of Huntington.

AVALANCHE PROBLEM: Persistent Slabs are the primary avalanche concern today. These slabs exist as both as hangfire from the natural avalanche cycles on Sunday and as pencil hard slabs from the wind loading on Tuesday. These are most likely to be found beneath the highly wind protected upper ice flows in the Tuckerman Headwall area. The second threat is from softer wind slab that developed as winds died down on Tuesday. Look for these smaller, but touchier slabs (1F hardness) behind terrain features in strong lee areas such as lookers left at the top of Right Gully, and along steep buttresses.

WEATHER: Weather will start transitioning late today from the clear high pressure system to increasing clouds with the approaching low pressure from the south. However, nice weather will continue for a day in the mountains and should not affect snow stability. An increasing wind may move just a little alpine snow, but not enough to load in as a new problem. Late tomorrow and into the early Sunday morning we will pick up some new snow, albeit scant.

SNOWPACK: Field time yesterday and a lot of discussion led us to settle on a Low rating today despite the fact that Persistent Slabs more often than not for us earn a Moderate rating. The main driver behind the Low rating is that the persistent weak layer of facets in question was discontinuous in nature even before this last avalanche cycle. Persistent slabs are typically hard, stubborn and therefore resistant to a human acting as a trigger.  Although this is true for our current situation we also have limited weak layers keeping us from moving our concern to a higher rating.  In addition, we believe the tensile slab strength of varying depth is bridging over an occasional deeper facet layer or isolated graupel pool.  Intense spatial variability and the discontinuous nature of the slabs and weak layers lead us to believe isolated pockets of concern most accurately describe our snowpack. While you may find some smooth Q2 shovel shears among the wind slab layers you will generally find them “hard” and stubborn. There is a lot of bridging power in hard slabs like these. That said, I would be careful of any of these slabs sitting on top of ice flows such as in the Center Bowl area. As always, mitigate your exposure to avalanche threats by careful route selection.

Look for more terrain/conditions photos today on our Facebook page and possibly the new Flickr account if all goes well on the technology front. The Sherburne is not particularly enjoyable skiing unless you like hard snow and water bars. It is currently plagued with a brutal frozen rain crust on it’s upper half. Right Gully saw a half dozen skiers yesterday on firm but smooth and carvable snow. Many other areas such as Left Gully were much more bumpy due to wind whipped sastrugi. Chris is writing what may be his last weekend update today….look for that later 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 8:40 a.m. January 23, 2015. A new advisory will be issued tomorrow.

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

2015-01-23 print friendly

Avalanche Advisory for Thursday, January 22, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Moderate and Low avalanche danger. Right Gully, the Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanche are possible. Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully to identify features of concern. The Lobster Claw, Lower Snowfields and the Little Headwall have Low avalanche danger. In these areas, natural and human-triggered avalanches are unlikely, but watch for unstable snow in isolated terrain features.

Huntington Ravine has Moderate and Low avalanche danger. Central and Pinnacle Gullies have Moderate 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. All other forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely; however, watch for unstable snow in isolated terrain features.

AVALANCHE PROBLEM: Wind Slabs that developed on Tuesday coupled with the hang fire from the avalanche cycle on Sunday night are the primary concerns today. Of particular concern would be the upper start zone of Right Gully, Sluice and the Lip. Most of the wind slabs are likely to be stubborn and resistant to triggering. A close second to these wind slabs are sluff piles beneath steep features which did not avalanche or were reloaded on Tuesday such as in Center Bowl and Chute. Huntington was more scoured by these winds, which were near 100 mph (160 km/h), on Tuesday. That said, Central and Pinnacle should be assessed for remaining wind slabs.

WEATHER: Highs in the teens F today coupled with light winds out of the west will do little to affect snow stability in either direction today. Winds are expected to shift from the W to NW and ramp up a bit from it’s current calm 5 mph (8 km/h) to around 30 mph (50 km/h) with higher gusts through the afternoon and evening.

SNOWPACK:  As Chris discussed yesterday, a wide range of snowpack issues exist in the Ravines. Not much has happened since then to either increase or decrease stability. A wet snow and freezing rain storm on Sunday was responsible for a widespread avalanche event on slopes and gullies with a more northerly facing aspect. The good news is that in many areas the cycle swept out the older persistent grain types associated with the January 4 crust.  However, Sundays snow/freezing rain line was right around the bottom of the Ravines and is already producing another layer of facets. A frozen crust also capable of producing these facets may have developed in some slightly higher elevations in the Ravines as well but its extent remains to be fully understood. Travellers should remember that firm or hard wind slabs that exist in many areas now can still be triggered if the right sweet spot is found. Often that spot is a thinner part of the slab. Multiple quick hand pits and continual assessment of your position relative to the hazard are more helpful in cases like these than one deep pit.

Sections of the Sherburne trail are very icy due to the freezing rain on Sunday.

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. January 22, 2015. 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

2015-01-22 print friendly

Avalanche Advisory for Wednesday, January 21, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Moderate and Low avalanche danger. Right Gully, the Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway have Moderate avalanche danger.  Natural avalanches are unlikely and human-triggered avalanche are possible.   Heightened avalanche conditions exist on specific terrain features. Evaluate snow and terrain carefully to identify features of concern.   The Lobster Claw, Lower Snowfields and the Little Headwall have Low avalanche danger. In these areas, natural and human-triggered avalanches are unlikely, but watch for unstable snow in isolated terrain features. Varying levels of instability exists within the Moderate rating.

Huntington Ravine has Moderate and Low avalanche danger. Central and Pinnacle Gullies have Moderate 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. All other forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely; however, watch for unstable snow in isolated terrain features. These pockets do exist. 

AVALANCHE PROBLEM: New Wind Slabs that developed over the past 24-48 hours are the #1 problem today. High winds yesterday continued to move snow from alpine areas down into both Ravines. Some of this was left over treeline snow still available from the main storm event Sunday night.  This mixed with new graupel and rimed stellars that fell during upslope snowfall Monday afternoon and very early Tuesday morning. The graupel may have pooled on some benches and other holding locations acting as a weak layer.  Older Wind Slab that survived a widespread avalanche cycle Sunday night is avalanche problem #2.  A number of areas that developed slab during Sunday night still exist intact.  These may be found either as hangfire above crown lines, such as in the Sluice, or some larger areas that did not avalanche such as in Right Gully.  A number of locations such as across the Tuckerman Headwall have these 2 problems combined with recent slabs over slabs that are +/- 60 hours old.

WEATHER: A storm Sunday night and Monday morning brought approximately 13″ (32.5cm) of snow to upper elevations, melting down to 2.5″ (6.25cm) of water.  This high density snow has plastered the landscape creating a very wintry scene indeed. High winds yesterday, peaking at 94mph (150kph), continued new loading into the afternoon.  Slackening wind speeds overnight shut down snow movement revealing a crisp morning view of the mountain.  Today, winds will continue falling, perhaps below 20mph (32kph), under clear warming skies.  This may help some consolidation of the snowpack, particularly on S facing slopes.  This tranquil trend should persist through tomorrow

SNOWPACK:  Yesterday’s sluffing that triggered an avalanche from Sluice down into the lower Center Bowl is a good indicator that instabilities still exist from this last precipitation event.  The Moderate ratings in many locations have just come down from the Considerable danger last night.  The spatial variability that exists have some Moderate forecast areas being on the lower end of the rating and others bumping the ceiling of the definition, but in both scenario’s “Moderate” is the appropriate call. Within the Moderate forecast areas you will find varying levels of unstable snow so it continues to be “Heads Up” conditions, demanding respect and frequent assessments.  Tuckerman’s “Lip” and “Center Bowl”, under the main headwall ice, are locations that harbor more propagation potential and issues than others, such as Right and Left gully.   Adding complexity to the equation is the question of surviving facets.  The avalanche cycle from this last storm has cleared out some of the facets we have been watching since the January 4th wet event.  However, where they still exist, avoiding the avalanche cycle clean out, may be trigger spots that are very difficult to recognize.  A number of debris piles are noticeable under chutes and snowfields providing clues to facet locations, although don’t give us all the answers.  Above these piles many fracture lines were reloaded during the storm.  This makes it difficult to assess where some facet weaknesses still exist in the hangfire above old crown lines, which are now indiscernible.  I kept this facet topic and persistent concern out of the avalanche problem discussion because it is a distant #3 issue.  That said, it is important to understand as a complicating factor for the skilled user to plug into their spatial variability assessments and travel decisions.  In Huntington, the majority of areas are posted at Low which is appropriate, but it is important to pick out isolated instabilities.  Odell and the Fan, approaching North, Damnation, and Yale gullies, are a couple of examples that have pockets of concern that can be avoided by adjusting your route. The temperate weather conditions over the next 48 hours will likely draw people into the hills.  It will be very important to stay vigilant in assessing mountain hazards such as avalanche potential to recognize lingering cold unstable wind slab and deeper weaknesses.

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. January 21, 2015. A new advisory will be issued tomorrow.

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

2015-01-21

Avalanche Advisory for Tuesday, January 20, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Considerable, Moderate, and Low avalanche danger. Right Gully, Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Lobster Claw has Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanche are possible. Lower Snowfield and Little Headwall have Low avalanche danger. In these areas, natural and human-triggered avalanches are unlikely, but watch for unstable snow in isolated terrain features.

Huntington Ravine has Moderate and Low avalanche danger. Central and Pinnacle Gullies have Moderate danger. Natural avalanches are unlikely and human-triggered avalanches are possible. All other forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely; however, watch for unstable snow in isolated terrain features.

AVALANCHE PROBLEM: Wind slabs are the greatest threats today, as well as slabs formed from piles of recent sluffing found near the transitions from steep terrain to slightly less steep terrain. Examples of where you may see the sluff-slabs are at the base of Pinnacle Gully or beneath the ice in the Sluice. In fact, as I write this, the slab beneath the Sluice just avalanched. That’s “bulls-eye” information about the existence of stability problems. Wind slabs can be found in a variety of locations. There is currently a large amount of snow being blown around the tops of both ravines; you’ll want to know the extent to which this is contributing to development of unstable slabs.

WEATHER: A storm Sunday night and Monday morning brought a lot of moisture to the mountains. At Hermit Lake we measured 2.3” (5.9cm) of water equivalent, which was a bit more than forecast. The type of precipitation that fell varied greatly at different elevations. A stout ice crust is found at elevations around Harvard Cabin, from Hermit Lake up to Lion Head the crust is more like refrozen ice pellets, and above Lion Head precip fell as mostly heavy dense snow. It seems as though the dividing line between all snow and mixed precip was somewhere around the tops of the ravines, so the surfaces in the ravines themselves did not escape without some mixing and crust formation. Also, an inch or two of (2.5-5cm) of rimed stellars fell mid-day yesterday. Today’s wind at 70-90mph with higher gusts will continue to fetch this snow from the alpine zone and redistribute it around the mountain.

SNOWPACK: Much of the terrain in locations rated Low already shows signs of being scoured and hammered by strong winds. In these areas, keep an eye out for protected pockets that may have held onto wind-loaded snow and formed smaller unstable slabs.

In the Considerable rated areas, you may find that a lot of the snow is encapsulated in the crust. Where this is the surface condition, the snow will be relatively stable, although in the thinner spots it is possible that you’ll encounter some of the worst breakable crust imaginable. What you need to be alert for are the locations that held onto snow as it loaded into avalanche start zones. We found this yesterday at the top gullies along the Lion Head Trail, where soft slabs over 1m deep had been able to form. Additional loading is definitely taking place today, at least in protected locations.

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 9:00 a.m. January 20, 2015. A new advisory will be issued tomorrow.

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

2015-01-20-FINAL

 

Avalanche Advisory for Monday, January 19, 2015

This advisory expires tonight at 12:00 midnight.

All forecast areas of Tuckerman Ravine and Huntington Ravine have CONSIDERABLE avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Careful snowpack and weather evaluation, cautious route finding and conservative decision-making are essential. Lobster Claw, Lower Snowfields and the Little Headwall are not posted due to lack of snow coverage.

AVALANCHE PROBLEM: Wind slab avalanches are threat #1 today. 1-3” of new snow plus 8” in the past 24 hours with increasing winds today will build wind slabs which are likely to be reactive to human triggers or become thick and heavy enough to avalanche naturally. Persistent slabs, which were weakened by yesterday’s warming trend, are a distant second to the primary threat but could easily contribute to the mass of snow available to an avalanche in the wind slab.

WEATHER: WNW then NW winds are expected to increase into the 100 mph (160 kph) range later today and into the night. Before we reach that high velocity, which often scours out much of Huntington and many areas in Tuckerman, we will pass through velocities ideal for loading lighter, new snow into the ravines. Visibility will be limited by summit fog and blowing and drifting snow. Temperatures will reach down to around 10F (-12C).

SNOWPACK: Recreationalists and our snowpack dodged a bullet yesterday when precipitation fell as snow instead of rain above the 3800’ level. Due to the heavy nature of the 8” (20cm) which fell yesterday and yesterday evening, the wind loading period today may be prolonged. The 4” of snow yesterday afternoon was around 25% density and fell on top of the earlier 4” of 20% density snow. The new snow falling through the day today will be much lighter than the snow being wind loaded into the terrain later. This structure will be a classic “upside down” structure as the denser snow is loaded on top of an already inverted snowpack.

Yesterday’s snow was dense enough at Hermit Lake to form a firm crust but lower temperatures on the summit and Alpine Garden yesterday allowed this snow to remain drier and therefore more prone to be moved by the wind today. It will be worth considering the weak layer of facets widely distributed through the terrain as well as areas of older wind slab in Sluice through Chute that could be activated by an increased load of new wind slab. It will be a heads up day for making field assessments or traveling around in either ravine.

The Sherburne had picked up a couple inches of new snow overnight but some of the water bars and stream crossing are just beginning to refreeze.

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 9:00 a.m. January 19, 2015. 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

2015-01-19

Avalanche Advisory for Sunday, January 18, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine will have Considerable and Moderate avalanche danger today. The Sluice, Lip, Center Bowl, Chute, Left Gully, and Hillman’s Highway will have Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Right Gully will have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Natural and human triggered avalanches are unlikely. The Lobster Claw, Lower Snowfields and Little Headwall are not posted due to a lack of snow.

Huntington Ravine will have Considerable and Moderate avalanche danger. Central, Pinnacle, Odell, and South gullies will have Considerable danger. Natural avalanches are possible and human triggered avalanches are likely. North Gully, Damnation, Yale and the Escape Hatch will have Moderate danger. Natural avalanches are unlikely and human triggered avalanches are possible.

AVALANCHE PROBLEM: Today’s ratings are primarily based on incoming snow late today, therefore storm slabs are threat number one. The new snow is expected to fall mainly in the afternoon and overnight, so the storm slab problem will be causing the avalanche danger to rise up to their posted ratings near the end of daylight or slightly beyond, from where they are starting the day, i.e. Low or Moderate. This problem is going to impact N, NE, and E aspects the most, such as Hillman’s, Left Gully, and Chute in Tuckerman or South, Odell, Pinnacle, and Central in Huntington.

Early birds getting out before any new accumulations and slab development should be alert for existing wind slabs and persistent slabs that we have discussed in previous avalanche advisories. These problems are dispersed around the terrain with a great deal of spatial variability. Tuckerman’s Lip and Sluice yesterday held the most newly developed wind slab followed by the north side of the Huntington Fan, whereas in all other areas persistent slabs existed.

WEATHER: It’s been a slow month for snowfall in the White Mountains, which leads to eager anticipation of the incoming weather. I’ll leave you to read the forecast for yourself, but the avalanche-related highlights include 0.2-0.4″ (5-10mm) of water equivalent forecasted through 7pm today and another 0.8-1.35″ (20-34mm) from 7pm to 7am. If temperatures were colder, this would be a lot of snow. Much to our dismay, warmth will prevent us from choking on powdery face shots. Most of this precipitation is coming in overnight, but how much falls during the day and early evening will determine how far the actual hazard goes up the danger rating scale. Another key factor will be whether or not it remains snow, mixes with sleet, or becomes either freezing rain or plain rain. Through today, winds will be slowly shifting from the WSW to the S at good speeds for loading snow and creating slab.

SNOWPACK: Prior to incoming snow, much of the avalanche terrain consisted of strong, wind-scoured snow. Some locations had stiff persistent slab as well, and in other areas there were a varying amount of faceting taking place beneath the surface snow. The extent of the faceting and the strength of the snow above had led us to danger ratings in the Moderate to Low range, depending on the location. As usual, the ravines offer a wide variety of snowpack situations, especially if you were to put in the effort to get to some of the harder to reach locations.

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 8:30 a.m. January 18, 2015. A new advisory will be issued tomorrow.

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

2015-01-18

Avalanche Advisory for Saturday, January 17, 2015

This advisory expires tonight at 12:00 midnight.

Tuckerman Ravine has Moderate and Low avalanche danger. The Sluice, Lip, Center Bowl, and Chute have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. All other forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely, although unstable snow in isolated terrain features may exist.

Huntington Ravine has Low avalanche danger. All forecast areas have Low avalanche danger. Natural and human-triggered avalanches are unlikely, although unstable snow in isolated terrain features may exist.

AVALANCHE PROBLEM: Persistent Slabs and Wind Slabs are jockeying for position as the greatest threat depending on your location. Huntington was mostly scoured by high winds yesterday leaving pockets of wind slab on approaches through the Fan with a smattering Persistent Slabs elsewhere. Central Gully is well worth making a careful assessment for a weak layer of facets beneath harder, old slabs. Tuckerman Ravine received more snow and less scouring yesterday, with softer wind slabs a potential problem in the entrance of Right, the Sluice bowl, the Lip area where the trail traverses, across the Bowl and lower Chute. Persistent Slabs in these locations are still a threat, particularly in areas which picked up an additional load of wind slab. Left Gully is mostly scoured, particularly at the top above the choke point. Hillmans is still lacking snow, though the upper third has the most wind loaded area and, like any other Low rated area, should be assessed carefully. Lobster Claw, Lower Snowfields and the Little Headwall have very little snow.

WEATHER: Good visibility and pinkish-orange alpenglow is the reward for suffering through the well below zero F temperatures this morning which were -11F (-24C) at 7am and -24F (-31C) at 5am. Clouds will return to the summits this afternoon with temperatures rebounding to 5F (-15C) on the summit, a bit warmer below treeline. Wind speeds in the 60 mph (85 kph) range with gusts to near 80 mph (120 mph) this morning will diminish a bit this afternoon but will remain challenging for folks above treeline. Winds may then increase again later this evening.

SNOWPACK: Intense snow squalls yesterday morning dropped about an inch and a half (3.8cm) of new snow over the course of a few hours. High winds yesterday scoured most of this new snow out of Huntington Ravine and unloaded or hammered down the existing wind slabs. Over the past ten days, small amounts of accumulated snow from snow shower activity was slow to stabilize. Favorable conditions for the development of weak faceted snow beneath the Jan 4th ice crust resulted in older wind slabs becoming a persistent slab problem. Widely variable slab thicknesses and the stubborn and strong nature of these slabs combined with a lack of human-triggers in much of the terrain has allowed us to avoid avalanche activity so far this week but has done little to ease our minds about this weak layer. Avalanche conditions such as these don’t shout danger but definitely remain a threat, particularly to the unwary.  Tuckerman, being slightly lower and more leeward than Huntington, gained more wind slabs yesterday than it lost. This new loading adds to the stress and strain on existing persistent slabs as well as increasing the potential consequence if a slab is triggered. The stronger lee position of the Moderate rated areas of Tuckerman is conducive to making these slabs more touchy and prone to human triggering so be wary of people above you and assess your exposure to these slabs.

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 8:30 a.m. January 17, 2015. 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

2015-01-17 print friendly