Avalanche Advisory for Sunday, December 31, 2017

Huntington Ravine has MODERATE and LOW avalanche danger. Central, Pinnacle, Odell, South, and Escape Hatch have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully, identify features of concern. North, Damnation, and Yale gullies have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

Tuckerman Ravine has MODERATE and LOW avalanche danger. Sluice, Lip, Center Bowl, Chute, Left, and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully, identify features of concern. Lobster Claw, Right Gully, Lower Snowfields, and the Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

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

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

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

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This bulletin is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
• Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast. For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or Harvard Cabin.
• Posted 7:40 a.m., Sunday, December 31, 2017. A new advisory will be issued tomorrow.

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

2017-12-31

Avalanche Advisory for Saturday, December 30, 2017

Huntington Ravine has MODERATE and LOW avalanche danger. Central, Pinnacle, Odell, South, and Escape Hatch have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully, identify features of concern. North, Damnation, and Yale gullies have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

Tuckerman Ravine has MODERATE and LOW avalanche danger. Sluice, Lip, Center Bowl, Chute, Left, and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully. Lobster Claw, Right Gully, Lower Snowfields, and the Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

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

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

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

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This bulletin is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
• Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast. For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or Harvard Cabin.
• Posted 7:45 a.m., Saturday, December 30, 2017. A new advisory will be issued tomorrow.

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

2017-12-30

Avalanche Advisory for Friday, December 29, 2017

Huntington Ravine has Moderate and Low avalanche danger. Central, Pinnacle, Odell, South, and Escape Hatch have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully, identify features of concern. North, Damnation, and Yale gullies have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

 Tuckerman Ravine has Moderate and Low avalanche danger. Sluice, Lip, Center Bowl, Chute, Left, and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human triggered avalanches are possible. Evaluate snow and terrain carefully, identify features of concern. Lobster Claw, Right Gully, Lower Snowfields, and the Little Headwall have Low avalanche danger. Natural and human triggered avalanches are unlikely. Watch for unstable snow on isolated terrain features.

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

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

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

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

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This bulletin is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
• Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast. For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or Harvard Cabin.
• Posted 8:00 a.m., Friday, December 29, 2017. A new advisory will be issued tomorrow.

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

2017-12-29

Avalanche Advisory for Thursday, December 28, 2017

This advisory expires at Midnight.

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

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

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

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

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

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This bulletin is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
• Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast. For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or Harvard Cabin.
• Posted 7:35 a.m., Thursday, December 28, 2017. A new advisory will be issued tomorrow.

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

2017-12-28

Avalanche Advisory for Wednesday, December 27, 2017

This advisory expires at Midnight.

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

 Tuckerman Ravine has CONSIDERABLE and MODERATE avalanche danger. Sluice, Lip, Center Bowl, and Chute have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential. Lobster Claw, Right Gully, Left Gully and Hillman’s Highway have Moderate avalanche danger. Natural avalanches are unlikely and human-triggered avalanches are possible. Lower Snowfields and Little Headwall in Tuckerman have Low avalanche danger due to lack of a developed snowpack. Watch for unstable snow on isolated terrain features such as Dead End and Duchess above the Lower Snowfields.

AVALANCHE PROBLEM: Wind slabs exist through the terrain today following 11” of new snow in the past 48 hours. Sustained 60 mph westerly wind continued to load new snow into our avalanche start zones yesterday and will likely continue to do so today as they are now. Expect a mix of densities in these slabs from finger hard and stubborn to four finger and more sensitive to triggering. Considerable rated areas have a history of prolonged wind loading due to available snow in a W or NW wind so remain elevated today. Natural avalanches are a little more unlikely than possible but careful assessment and snowpack evaluation would be required to confirm. Our slopes continue to grow in area, creating the opportunity for larger avalanches. If you plan to brave the cold today to climb or ride in the Ravines, bring your A game.

WEATHER: The cold temperatures that are making headlines will make for challenging conditions on the mountain today. It is currently -23F on the summit with winds from the west in the low 70 mph range. Temperatures will warm slightly as wind diminish a bit today before plummeting again tonight as wind from the NW increase to near 100 mph. That ugly sweater that was too much for Christmas may be just right today.

SNOWPACK: The summit recorded 1.5” in the past 24 hours. The new snow added to the wind loading that has occurred in the past 48 hours following 9” that fell on the 25th. Limited visibility denied us a view of the upper start zones in Huntington and the bowl in Tuckerman but did allow some other avalanche observations. As expected, the ice crust encasing the 9” of snow that fell on the 22nd/23rd broke down and contributed that snow to the most recent avalanche cycle. This allowed Hillman’s Highway to avalanche around the corner, and Central, Odell’s and South to push pretty far towards the floor. It seems likely that other forecast areas avalanched as well but limited visibility has made closer observations unsafe.

The Lion Head Winter Route is open and the preferred route to the summit from the east side. Remember that natural or human-triggered avalanches can run out onto the floor of Tuckerman Ravine. Keep a safe distance if hiking up to have a look around.

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This bulletin is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
• Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast. For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.
• Posted 8:05 a.m., Wednesday, December 27, 2017. A new Advisory will be issued tomorrow.

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

2017-12-27

Avalanche Advisory for Tuesday, December 26, 2017

Huntington and Tuckerman Ravines have CONSIDERABLE avalanche danger. Natural avalanches are possible and human triggered avalanches are likely. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route finding, and conservative decision making are essential. Lower Snowfields, and Little Headwall in Tuckerman are the exception with Moderate avalanche danger due to a less developed snowpack. Natural avalanches are unlikely and human triggered avalanches are possible. Heightened avalanche conditions on specific terrain features.

 AVALANCHE PROBLEM: Yesterday’s snow and wind has built wind slabs over much of our terrain that will vary in hardness and sensitivity. Wind transport is still occurring and will continue for any snow that falls today. Accordingly, our surface wind slabs will continue to change in distribution, size, and character through the day. If you brave cold and wind today you will likely find at least some areas of greater stability, but the dynamic nature of our current surface snow will combine with compromised visibility to make safe travel in avalanche terrain challenging.

 WEATHER: Our Christmas day storm brought 9” of new snow to the summit. W wind in the 60-90 mph range has dominated since yesterday afternoon and will continue today. Show showers today bringing up to 4 more inches of snow which will alternate with occasional partial clearing. Current temperatures in the negative single digits F should steadily creep down through tomorrow morning. The summit will approach -30F. Windchill values could bottom out near -80F. Remember, small problems quickly turn into big problems in this weather. As always, consider the realistic consequences of something going wrong.

SNOWPACK: Poor visibility limits our ability to make observations this morning, though we expect our snow surface is comprised of a variety of firm to very firm wind slabs, with pockets softer snow and exposed crust. The extended summit wind over 80 mph yesterday and forecast to remain high today will have easily transported and compacted much of the low density new snow. The potential for additional snow up to 4” today should be similarly transported. The high density wind slabs we see following these wind events is often supportable and heavily textured on the surface. Such slabs should be stubborn to a human trigger, but the pockets of softer and smoother snow that we skiers and riders seek will be more sensitive in all but select locations. Further, we still expect avalanches to break up the crust formed a few days ago and entrain softer snow beneath it. Below this crust and softer snow, widespread hard slabs that would likely take a massive load to trigger limit our concerns for deep instability. We likely had a widespread avalanche cycle in the last 24 hours, evidence of which we may or may not see today with limited visibility and active reloading of these same avalanche paths.

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

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This bulletin is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
• Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast. For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.
• Posted 8:00 a.m., Tuesday, December 26, 2017. A new Advisory will be issued tomorrow.

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

2017-12-26

Avalanche Advisory for Monday, December 25, 2017

Huntington Ravine has HIGH and CONSIDERABLE avalanche danger. Central, Pinnacle, Odell, and South Gullies will reach High avalanche danger. Natural avalanches likely and human triggered avalanches very likely. Travel in avalanche terrain is not recommended. All other areas in Huntington will reach Considerable avalanche danger. Natural avalanches are possible and human triggered avalanches are likely.

 Tuckerman Ravine has HIGH avalanche danger. Natural avalanches likely and human triggered avalanches very likely. Travel in avalanche terrain is not recommended. Lower Snowfields and Little Headwall in Tuckerman are the exception with Moderate avalanche danger due to a less developed snowpack. Heightened avalanche conditions on specific terrain features.

 AVALANCHE PROBLEM: Today’s significant storm snow and wind will build reactive wind slab over terrain lee to W and NW wind and crossload other aspects by this evening. Lighter winds this morning coupled with heavy snowfall could allow a less cohesive storm slab to briefly develop. Before this becomes much of a concern, wind speeds will rise and build the more cohesive and reactive slabs that are our primary avalanche problem. Instability will likely peak this evening before sustained extreme wind overnight scours many areas and builds firmer and more stubborn slabs. There is a strong chance that avalanches today will break up Saturday’s crust and entrain soft snow below, resulting in a larger slide than surface slabs might suggest. Areas not receiving a High danger rating today lack the snowpack development to produce a large avalanche, though the likely but smaller human triggered avalanches in these areas could still have dire consequences.

 WEATHER: We’re all getting a heap of snow for Christmas! It’s coming down already and by tomorrow we will likely have over a foot of new snow on the mountain, with heaviest snowfall earlier in the day today. Southerly wind in the mid-30’s mph range during the heaviest precipitation will increase and shift through W to NW as snowfall tapers but continues through today and tonight. Sustained wind speeds over 70 mph with gusts nearing 100 mph can be expected. Summit temperatures will trend downwards from single digits above to single digits below zero. Light snow will continue tomorrow as W to NW wind continues to push the century mark. This weather follows a major crust building event on Friday and a subsequently unremarkable Christmas Eve. Limited snow was available for wind transport yesterday, but plenty will be today.

SNOWPACK: Today’s storm will be deposited on a layer of 1-2 cm breakable crust that formed Friday evening and exists on most of our terrain. The snow that fell earlier on Friday remains soft and dry beneath this crust. We expect avalanches today to occur above the crust, but realize that any sizable avalanche will break up this crust and entrain Friday’s storm snow below it. The avalanches that are likely to occur today will likely be large relative to current path development. It’s a great day to recreate in the snow without exposing yourself to avalanche terrain. The John Sherburne Ski Trail now has good coverage and should ski well as the new snow accumulates!

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

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This bulletin is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
• Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast. For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.
• Posted 8:00 a.m., Monday, December 25, 2017. A new Advisory will be issued tomorrow.

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

2017-12-25

Avalanche Advisory for Sunday, December 24, 2017

Huntington and Tuckerman Ravines have MODERATE avalanche danger. All forecast areas have Moderate avalanche danger. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully to identify features of concern. Lower Snowfields and Little Headwall in Tuckerman are the exception with Low avalanche danger due to lack of a developed snowpack. Natural and human triggered avalanches are unlikely there.

 AVALANCHE PROBLEM: Previously existing wind slab and sluff piles beneath steep features were encased in ice yesterday afternoon. A brief visit to Hillman’s this morning in low visibility conditions revealed that you could find, and posthole into, areas of soft, dry snow beneath a glaze of ice in lots of areas. One of the concerns that would be on my radar today would be some of the large piles of sluff sitting beneath funnel points in our steepest terrain. An outside chance of perforated the ice and being the trigger on one of these wind slab/sluff piles would be enough to keep me from traveling alone or leaving my beacon, probe and shovel in the car. Additionally, light snow fall continues this morning and may build small wind slabs in lee areas.

 WEATHER: It should be no secret that we saw a mixed bag of precipitation yesterday. At Hermit Lake, around 5” of snow fell before the storm switched over a crust building rain and frozen precipitation mix in the afternoon. Temperatures hovered just below freezing with southerly wind around 40 mph through the bulk of this storm. Precipitation tapered off overnight, summit temperature dipped to the current single digits above zero F, and wind shifted through W to NW increasing to the current 70 mph. Today’s break between storms should be accompanied by temperatures in the teens, mostly cloudy skies, and a wind that will eventually decrease as it shifts through W and S to SE as snowfall begins tonight. A significant storm in the next 36 hours looks to bring a storm total of around a foot of new snow on southerly wind that will shift NW and elevate as snowfall tapers off. It certainly looks like a white Christmas!

SNOWPACK: A breakable freezing rain crust of 1-2 cm thickness is our primary surface from the lower mountain up to the floor of the ravines. We believe that this crust is pervasive through our upper terrain, though visibility limits our current ability to confirm this. Beneath this crust formed yesterday afternoon much of our terrain will hold the comparatively dry snow that fell prior to crust formation. This snow will vary in thickness from several inches to more than a foot. Though you would be hard pressed to trigger an avalanche today in this snow it will likely be a player in tomorrow’s avalanches. The significant snow and wind coming Monday could produce avalanches on this crust that would ultimately break it apart and entrain the soft snow below.

The Lion Head Winter Route is open and the preferred route to the summit from the east side. Daylight hours are short today…don’t forget to adjust your turn around time and headlamp. Expect to posthole into soft snow beneath the crust if travelling off the beaten path.

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This bulletin is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
• Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast. For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.
• Posted 8:00 a.m., Sunday, December 24, 2017. A new Advisory will be issued tomorrow.

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

2017-12-24

Volunteer help needed

As some of you may know already, our avalanche forecasting operation involves much more than snow study field work and sipping coffee while studying weather data on the internet. Our work is complicated by maintaining the equipment and trails necessary to provide for search and rescue response as well. Not only does this equipment, need maintenance, it also breaks down or is inefficient. We have some upgrades in the works that we hope will make the logistics of gathering and posting information more streamlined, which should free us up to pursue other important projects, like more in-person and virtual outreach and education efforts. Put we need a reliable power supply to do it.

One of the current projects that will help us out alot is to upgrade our electrical situation in the cabin at Hermit Lake. We have a recently purchased inverter and some batteries to pair with our generator and existing wiring and breaker panel that we’d like to install, but we haven’t the time, or frankly, the skills to do it. If you or someone you know is an electrician and could help us out, we’d love it. Please email me at mwactucks@gmail.com. -Frank

Avalanche Advisory for Saturday, December 23, 2017

Huntington and Tuckerman Ravine have CONSIDERABLE avalanche danger. All forecast areas have Considerable avalanche danger. Natural avalanches are possible and human-triggered avalanches are likely. Dangerous avalanche conditions exist. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential. Lower Snowfields and Little Headwall in Tuckerman have Low avalanche danger due to lack of a developed snowpack. Natural and human triggered avalanches are unlikely there. Watch for unstable snow on isolated terrain features such as Dead End and Duchess above the Lower Snowfields.

AVALANCHE PROBLEM: New snow yesterday created some wind slabs throughout the terrain. These slabs were built from low density snow on light to moderate winds and will remain touchy this morning. Furthermore, this snow comes with a lump of coal in your stocking. Warming temperatures, sleet and possibly a bit of rain will begin to load the new snow and wind slabs making them even more sensitive to a human-trigger and increasing the likelihood of natural avalanches. There are enough areas of softer snow from earlier in the week so it’s possible that an avalanche could entrain more snow than just yesterday’s snowfall. If you survive the freezing rain glazed roads to get to the mountain, you’ll have your hands full staying safe due to this mix of avalanche problems!

WEATHER: Snow will continue this morning before warm air overriding cold air at ground level brings sleet, then freezing rain to all elevations.  We may even see a greater variety in precipitation types, including plain old rain, as today’s weather brings nearly 0.5” water. Wind should remain moderate out of the S to SW through daylight hours. As precipitation winds down tonight, expect wind to shift to W then NW and increase to around 60 mph. This wind is forecast to continue through tomorrow, when we will also see a break in precipitation, partial cloud cover, and temperatures back down into the teens.

SNOWPACK: In the past 24 hours, the snowplots at 3800’ recorded around 15cm of 5.5% density snow with 8” recorded on the summit. Steady light to moderate snow (S-1 to S1) fell through yesterday starting at around 9am. The low density snow provided lots of good skiing on lower angled areas low in Left and Hillman’s and in Huntington. All parties wisely avoided the steeper, and more wind loaded upper start zones where loading was happening and some instabilities lingered from previous snow this week. As is often the case with light snow in steep terrain, dry loose avalanches, a.k.a. sluffing, occurred and was reported to be sizeable in Yale Gully in the afternoon. This recent avalanche activity highlights the potential danger today.

The Lion Head Winter Route is open and the preferred route to the summit from the east side. Daylight hours are short today…don’t forget to adjust your turn around time and bring your headlamp!

Please Remember:
• Safe travel in avalanche terrain requires training and experience. This bulletin is just one tool to help you make your own decisions in avalanche terrain. You control your own risk by choosing where, when, and how you travel.
• Anticipate a changing avalanche danger when actual weather differs from the higher summits forecast. For more information contact the Forest Service Snow Rangers, the AMC at the Pinkham Notch Visitor Center, or the caretakers at Hermit Lake Shelters or the Harvard Cabin.
• Posted 8:00 a.m., Saturday, December 23, 2017. A new Advisory will be issued tomorrow.

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

2017-12-23