Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Thu, January 3rd, 2019 - 7:00AM
Expires
Fri, January 4th, 2019 - 7:00AM
Forecaster
Heather Thamm
The Bottom Line

The avalanche danger is  MODERATE in the Alpine and Treeline zones for triggering a large slab 2+’ thick in steep terrain. Give cornices a wide berth and avoid being under glide cracks. Natural glide avalanches are possible today and could release without warning.

There is LOW avalanche danger below 1000′ where a surface crust has strengthened the snowpack.

SUMMIT LAKE / JOHNSON PASS / LYNX DRAINAGE:    South of Turnagain Pass, keep in mind old buried weak layers exist and there is potential for triggering a large slab avalanche that breaks near the ground.

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Thu, January 3rd, 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

UPDATE: We just recieved a report of a large remote triggered avalanche in the Seattle Creek drainage that occured yesterday. We don’t have much info at this time and its unknown what layer this avalanche failed on. We do know that remote triggered avalanches are a sign of a persistent slab problem and it may be buried surface hoar. Keep this new info on your mind if you’re heading to Turnagain Pass.  

Cooling temps and light winds are helping to improve stability of wind slabs since the New Year’s storm dumped 2-3’ of snow and blasted our snowpack with hurricane force winds. Clear and sunny weather today will make it easy to identify smooth pillowed convexities, cross-loaded gullies, and hollow sounding snow – wind slab habitat. What makes this avalanche problem challenging is it’s transition into becoming a persistent slab. As this storm snow problem strengthens, a layer of buried surface hoar from Christmas remains on our minds. Hand pits yesterday were challenging to find this layer due to how deeply buried (2+’) it is in places. Many observations over the last week have been documenting the location of buried surface hoar and its presence and reactivity have been variable. With that said – triggering a wind slab on a mid-storm density change or on buried surface hoar are both possible today.

If you’re headed out, ease into steeper terrain with a conservative mindset. Evaluate terrain and snow as you travel and remember ‘whumpfing’ is an obvious clue of instability.

CORNICES:  There are some very large cornices along many ridgelines across our region. Triggering a cornice with the weight of a person or snowmachine is possible today. Remember these can break further back than expected. Give cornice features lots of space and avoid being directly under them.

 

A storm triggered slab from the New Years storm below Hippy Bowl on SW aspect of Tincan. Also note the wind sculpted snow in the alpine and cornice along the ridgeline.  

 

Avalanche Problem 2
  • Glide Avalanches
    Glide Avalanches
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
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.

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

Glide cracks exist in popular ski and snowmachine terrain and a may be tricky to identify with new snow covering them. Several glide cracks have avalanched this week and it’s possible more will release in the coming days. The best way to manage this problem is to avoid being under slopes with cracks opening up. They can release at any time and are not typically associated with human triggers. Glide avalanche have occurred in Lynx Creek, on Lipps, and Seattle Ridge this week.

 

 

A glide avalanche on Lipps SW face that released just before the New Years Storm is not covered by new snow and looks very different

Photo of Lipps glide crack taken yesterday (1-2-19). Although part of this crack has released the additional portion can still avalanche without warning.  

 

Additional Concern
  • Persistent Slabs
    Persistent Slabs
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.
More info at Avalanche.org

South of Turnagain:  A shallow and poor snowpack structure exists in the Summit Lake zone. Buried weak layers of facets associated with crusts sit near the base of the snowpack. An observation from Lynx Creek on Friday also found a reactive layer of facets mid-pack. Keep in mind Summit Lake has received additional loading from the New Years storm – strong winds and a foot of new snow. Recent avalanche activity and ‘whumpfing’ will be good reminders to keep terrain choices conservative in these zones. Triggering a larger avalanche that releases near the ground is not out of the question. Check out the Summit observations HERE for the more snowpack details.

Weather
Thu, January 3rd, 2019

Yesterday: Snow showers were observed in the morning with a trace of new snow at Turnagain Pass. Rain/snow line was near 300′. Light to moderate ridgetop winds from the East shifted to a NW direction by mid-day. Temperatures cooled in the upper elevations to low 20F’s/upper teens (F) as skies cleared in the afternoon.  

Today: A cooling trend will continue today as a high-pressure system establishes itself over Southcentral, Alaska. Expect temps at 3000′ to reach low teens/upper single digits today. Temperatures near sea level will drop into low 20F’s to teens by this evening. Northwest ridgetop winds will be in 5-15mph range. No precipitation is expected.

Tomorrow: A similar pattern of clear skies, cold temps and light NW winds will continue into the weekend.

*Seattle Ridge weather station was heavily rimed and the anemometer (wind sensor) was destroyed.    

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 25   trace   0   63  
Summit Lake (1400′) 23   0   0   22  
Alyeska Mid (1700′) 25 1   0.12   50  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 16   NW   5   26  
Seattle Ridge (2400′) 21   *N/A   *N/A     *N/A    
Observations
Recent Observations for Turnagain Pass
Date Region Location
12/10/19 Turnagain Avalanche: Tincan and Sunburst from the air
12/10/19 Turnagain Observation: Tincan
12/08/19 Turnagain Avalanche: Tincan
12/06/19 Turnagain Avalanche: Sunburst
12/04/19 Turnagain Observation: Sunburst
12/03/19 Turnagain Observation: Hippy Bowl
12/01/19 Turnagain Observation: Tincan, All elevations
12/01/19 Turnagain Observation: Tincan
11/30/19 Turnagain Observation: Tincan Treeline Plateau/ Common Bowl/ Ridge
11/29/19 Turnagain Observation: Sunburst Ob #2
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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