Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Fri, January 12th, 2018 - 7:00AM
Expires
Sat, January 13th, 2018 - 7:00AM
Forecaster
Heather Thamm
The Bottom Line

The avalanche danger is HIGH at all elevations above 1000′ due to a storm bringing new snow, strong winds and warm temperatures to our region. Natural and human triggered storm slabs 1-3′ deep will be likely today in avalanche terrain and may step down to an older more dangerous week layer. Travel is not recommended on slopes steeper than 30 degrees and in all runout zones.  

The avalanche danger is CONSIDERABLE below 1000′ where natural avalanches from above are possible in steep channeled terrain.  

**Portage and Whittier, outside of our advisory zone, are expected to receive double the amount of precipitation as Turnagain Pass. Avalanche activity in these zones may run to valley bottoms.    

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Fri, January 12th, 2018
Alpine
Above 2,500'
High (4)
Avalanche risk
Treeline
1,000'-2,500'
High (4)
Avalanche risk
Below Treeline
Below 1,000'
Considerable (3)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
High (4)
Treeline
1,000'-2,500'
Avalanche risk
High (4)
Below Treeline
Below 1,000'
Avalanche risk
Considerable (3)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Storm Slabs
    Storm Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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

Overnight a foot of new snow has fallen in the upper elevations of Turnagain Pass and Girdwood and another 10-20” of snow is expected today. This new snow combined with strong Easterly winds and warming temperatures will be forming unstable storm slabs and adding stress to preexisting weak layers within the snowpack. This new snow has fallen on surface hoar and near-surface facets and slabs are expected to be sensitive and easy to trigger. Below 2000’ these weak layers are sitting on a slick crust and could catch you by surprise in more protected areas and on small terrain features. Stormy weather today will be increasing the avalanche hazard, as slabs grown in size, and natural avalanches will become more likely as the day moves on.  Should you venture out today, stick it low angle slopes, less than 30 degrees and avoid being under the runout of larger slopes above. Shooting cracks and collapsing sounds “whumpfing” are expected and will be obvious signs the snow is unstable. This is a good day to ride in the flats and keep your terrain choices mellow. Don’t forget even small terrain feature can have high consequences. 

Shooting cracks observed yesterday during the beginning of the storm

 

 

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

Rapid loading due to new snow and winds will be adding stress to existing week layers within the snowpack. We have been tracking a layer of buried surface hoar from the New Year’s holiday, which still is showing propagation potential in test pits above 2500’. Triggering a storm slab could step down to this layer producing a large to very large avalanche depending on the size of the slope. In addition, a Deep Persistent Slab problem remains a concern in the upper elevations above 3000’, and serves as one of the many reason to not go into the alpine today. In fact – today is a great day to stay on low angle terrain and practice your rescue skills. 

 

Several week layers exist within the snowpack, additional reasons to avoid travel in avalanche terrain. 

 

Weather
Fri, January 12th, 2018

Snow started falling yesterday morning and continued overnight with 0.7 € of Snow Water  Equivalent  (SWE) at Center Ridge Snotel and 0.62 € SWE at Alyeska Midway station. Unfortunately the Snotel site was not recording height of snow this morning, but Alyeska midway station recored 11 € since yesterday.   Easterly ridgetop winds averaged in the 30’s mph with gusts reaching the 60’s mph on Sunburst. Gusty valley winds were also observed along the road corridor at Turnagain Pass. Temps gradually increased overnight with sea level temps reaching the mid 36F’s this morning and transitioning to rain just above sea level.  

Today 0.8 € SWE, another 10-12 € of snow is expected during the day and double this amount midnight. Winds will continue to blow from East, 20-40mph and temperatures are expected to continue to warm with high’s in the upper 30F’s at sea level. Rain/snow line is likely to bump up to 500′ by this afternoon.  

Tomorrow more rain and snow and Easterly winds are on tap as another front moves into our region. Temperatures are expected to increase into the 40Fs at sea level and rain/snow line will continue to move up in elevation, possibly as high as 1500′ by Sunday.

*New snow was estimated at Center Ridge Snotel based on similar SWE (Water inches) at Alyeska midway station.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 31   *12   0.7   *54  
Summit Lake (1400′) 29   0   0   15  
Alyeska Mid (1700′) 28   11   0.62   45  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 19   ENE   35   68  
Seattle Ridge (2400′) 23   SE   20   41  
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Riding Areas
Updated Mon, December 02nd, 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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