Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sun, February 10th, 2019 - 7:00AM
Expires
Mon, February 11th, 2019 - 7:00AM
Forecaster
Heather Thamm
The Bottom Line

The avalanche danger is MODERATE in the Alpine and Treeline zones. Triggering a fresh wind slab 6-12 € thick is possible on steep terrain features. Active wind loading could add stress to a more dangerous problem where triggering a large slab avalanche 2-3′ thick remains possible on steep slopes above 2,000′. These slabs can be triggered remotely from ridgelines and will be large enough to bury, injure or kill a person. Be on the lookout for shooting cracks and blowing snow, identify wind loaded aspects and avoid high consequence terrain. Give cornices a wide berth, and avoid travel under glide cracks.

SUMMIT LAKE / JOHNSON PASS: Areas south of Turnagain Pass harbor a thinner, weaker snowpack with multiple weak layers present including the MLK buried surface hoar. Blowing snow, whumpfing, shooting cracks or any signs of avalanche activity are reminders to avoid avalanche terrain.

LOST LAKE / SEWARD: Thursday we received a report of a human triggered avalanche where someone was caught, carried and injured on the Harding Icefield trail and suffered a minor head injury. This avalanche occurred, February 2nd. For more details read the accident report HERE. This area has very little snowpack info and extra caution is advised.  

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Sun, February 10th, 2019
Alpine
Above 2,500'
Moderate (2)
Avalanche risk
Treeline
1,000'-2,500'
Moderate (2)
Avalanche risk
Below Treeline
Below 1,000'
Low (1)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Moderate (2)
Treeline
1,000'-2,500'
Avalanche risk
Moderate (2)
Below Treeline
Below 1,000'
Avalanche risk
Low (1)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Likelihood of Avalanches
This graphic depicts how likely you are to trigger avalanches or encounter natural avalanches while traveling on avalanche prone slopes. Unlikely means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. The chance of triggering or observing avalanches increases as we move up the scale. Certain means that humans will be able to trigger avalanches on many slopes, and natural avalanches should be expected.

Size of Avalanches
This graphic depicts the potential size and destructive force of expected avalanches. Small avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become large enough to bury, injure, or kill people, large enough to bury or destroy vehicles and break a few trees, and large enough to destroy railway cars, buildings, or a substantial amount of forest. Historic avalanches are massive events capable of destroying villages and gouging or altering the landscape.
More info at Avalanche.org

Sunburst weather station is already reporting Easterly winds 15-25 with gusts in the mid 30s to low 40s mph. Roughly 4-6” of loose snow is available for transport and a few addition inches may fall throughout the day. Expect wind slabs 6-12” to form on leeward aspects and cross load terrain features. Visibility will make travel challenging today. Avoid wind loaded features and pay attention to blowing snow and shooting cracks. Triggering even a small wind slab in the wrong place could have high consequences. Don’t forget about the deeper more dangerous avalanche problem where triggering a small wind slab could step down into a much bigger persistent slab avalanche.

Avalanche Problem 2
  • Persistent Slabs
    Persistent Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

Likelihood of Avalanches
This graphic depicts how likely you are to trigger avalanches or encounter natural avalanches while traveling on avalanche prone slopes. Unlikely means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. The chance of triggering or observing avalanches increases as we move up the scale. Certain means that humans will be able to trigger avalanches on many slopes, and natural avalanches should be expected.

Size of Avalanches
This graphic depicts the potential size and destructive force of expected avalanches. Small avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become large enough to bury, injure, or kill people, large enough to bury or destroy vehicles and break a few trees, and large enough to destroy railway cars, buildings, or a substantial amount of forest. Historic avalanches are massive events capable of destroying villages and gouging or altering the landscape.
More info at Avalanche.org

The MLK buried surface hoar is roughly 1-3′ deep has been responsible for 13 human triggered avalanches over the past two weeks. The last one was four days ago on Eddies. On that day snowpack tests were pointing toward a stabilizing weak layer and then the 2′-3′ deep avalanche was triggered remotely from the ridge on a steep, unsupported slope. This avalanche illustrates that snow pit tests are unreliable for the current problem. Furthermore, no signs of instability have been seen in conjunction with several of the large human triggered avalanches on this layer.

Moderate winds will be adding additional stress to the snowpack and it is possible a person or snowmachine could tip the balance. Over the last few days many people have been pushing into steeper terrain without incident, but don’t forget this is the kind of avalanche problem where several tracks may be on a slope before someone finds a trigger point and the whole slopes avalanches.

What to keep in mind today:
1- This weak layer is widespread in the region and seems to be particularly suspect between 2000′-2500′ due to a melt-freeze crust associated with it.
2- Use safe travel protocol. Expose only one person at a time (this includes paying attention to other groups in the area), watch partners, stop in safe zones and be rescue ready.
3- Wind loaded steep features, large connected and unsupported slopes are the most suspect. As always, one can simply avoid high conseqence terrain and stick to slopes under 35 degrees with nothing steeper above to avoid the issue. 

A remote triggered slab on Eddies released on a layer of buried surface hoar on Wednesday (2/6/19.) We have been refering to this layer as the MLK buried surface hoar. It was buried on Martin Luther King day. 

 

Good example of how stability tests have been showing unreliable results. Some tests show propagation potential while other are not reactive in the same pit location. Cornbiscuit on 2/8/19.

Additional Concern
  • Glide Avalanches
    Glide Avalanches
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
More info at Avalanche.org

Glide cracks continue to creep open and are scattered across the region. The last glide crack to release into an avalanche was over a week ago in the Summit zone just north of Manitoba. Glide cracks are unpredictable, not associated with human triggers, and can release without warning at any time. There are areas where cracks are growing larger in popular terrain. PMS Bowl on Magnum is a good example of where the normal up-track is directly under a massive glide. Avoiding a glide crack could mean putting yourself into steeper terrain and exposing yourself to another avalanche hazard. This adds an extra challenge when weighing consequences of the terrain vs the avalanche hazard. Avoidance is the best way to manage this problem, but minimizing exposure under a glide may be your next best option if you stumble upon an unexpected glide.

 

Navigating the large glide crack in PMS is very difficult to avoid without getting into steeper terrain that may present other avalanche hazards. Something to consider if you decide to go to this area. 

Weather
Sun, February 10th, 2019

Yesterday: Skies were overcast with valley fog. Ridgetop Temperatures were in the upper 20F’s and reached a high of 34F with a brief appearance from the sun. Overnight upper elevation temps dipped to the low 20F’s. Temps at sea level were in upper 20F’s yesterday and increased to mid 30F’s overnight. Winds were light and variable becoming Easterly early evening and increasing to 15 to 35mph overnight.

Today: Low pressure moving through the Gulf of Alaska has brought a change in weather. Expect ridgetop winds in the 15-35mph with gusts in the 40’s mph. Skies will be overcast. Snow showers may produce a few inches of new snow (.17 € SWE) near Turangain Pass, 1-2 € of snow. Precipitation will favor Prince William Sounds and Portage with up to 6 € in the upper elevations. Temperatures will be in the mid 30F’s at sea level and Rain/snow line will be around 600′. Temps in the upper elevations will remain in the mid 20Fs.

Tomorrow: Skies are expected to be partly cloudy. Ridgetop winds will diminish in the morning and shift to the South, 5-15mph. Temps at sea level will be in the upper 20Fs to mid 30Fs with daily warming. Temperatures near ridgetops will range from the mid to upper 20Fs with daily warming. Evening snow flurries possible.

*The Seattle Ridge anemometer (wind sensor) was destroyed. We have a replacement on the way and it should be operational by mid February.

PRECIPITATION 24-hour data (6am – 6am)

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 29   0   0   58  
Summit Lake (1400′) 23   0   0   25  
Alyeska Mid (1700′) 28   0   0   50  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 27   ENE   10   41  
Seattle Ridge (2400′) 28   *N/A   *N/A     *N/A    
Observations
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Riding Areas
Updated Wed, December 11th, 2019

Status of riding areas across the Chugach NF is managed by the Glacier and Seward Ranger Districts, not avalanche center staff. Riding area information is posted as a public service to our users and updated based on snow depth and snow density to prevent resource damage at trailhead locations. Riding area questions contact: mailroom_r10_chugach@fs.fed.us

Area Status Weather & Riding Conditions
Glacier District
Johnson Pass
Closed
Closed.
Placer River
Closed
Closed.
Skookum Drainage
Closed
Closed.
Turnagain Pass
Closed
Closed.
Twentymile
Closed
Closed.
Seward District
Carter Lake
Closed
Closed.
Lost Lake Trail
Closed
Closed.
Primrose Trail
Closed
Closed.
Resurrection Pass Trail
Closed
Closed. Will be open for the 2019/20 season pending adequate snow cover.
Snug Harbor
Closed
Closed.
South Fork Snow River Corridor
Closed
Closed.
Summit Lake
Closed
Closed.

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