Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sun, March 4th, 2018 - 7:00AM
Expires
Mon, March 5th, 2018 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

The avalanche danger is  MODERATE  above 1000′ on all aspects. Lingering wind slabs (up to a foot thick) will be possible to trigger along with a larger slab avalanche (up to 2′ or more thick) that breaks in weak layers deeper in the snowpack. Sunshine today may trigger small wet loose avalanches on steep Southerly aspects.  

**If headed South of Turnagain Pass be aware of recent avalanche activity in Summit Lake and Lost Lake areas. Click  HERE  for the Summit Summary and click  HERE  for several observations from Lost Lake.  

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Sun, March 4th, 2018
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
  • 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

Finding and triggering a slab avalanche that breaks in weak snow 1-2+’ deep in the pack remains a concern. This could be in the form of a lingering wind slab or a much older slab that sits on weak layers in the mid-pack. Although today’s clear skies should reveal a dusting of new snow from yesterday, this is likely only enough to obscure a generally variable and wind affected surface through the region. With a longer sunny day ahead, here are the things to keep in mind:

Lingering wind slabs:  Strong Northwest winds impacted the region last week and due to unusual wind loading patterns, formed hard wind slabs on a variety of aspects. Watch for steep areas harboring stiff snow over softer snow and cracks that shoot out from you. Old wind slabs can be found along ridgelines and in steep rocky terrain, but also mid-slope in cross-loaded gullies. Even a small slab can have high consequences in steep and committing terrain. 

Persistent slabs:  Several weak layers sit in the middle and base of the snowpack and as recent as last Tuesday, skiers triggered a large ‘persistent slab’ in the Summit Lake area. This problem has shown to be more pronounced on the Southern end of Turnagain Pass and Summit Lake where the snowpack is shallower (areas to the North, such as Crow Pass, could also be suspect). Wednesday, during the wind event, numerous large avalanches released naturally near Silvertip Creek and in Summit Lake, most likely due to winds overloading these various weak layers. In short, buried 1-2 feet deep are facets sitting on a crust at the mid-elevations and buried surface hoar at the higher elevationsWhumpfing has been widely reported in the mid elevation band region-wide. If headed out for a long day in the mountains, remember these layers are there and no red flags may be present before a slab releases. 

Solar warming/effects:  Sunshine today along with light winds may allow for enough warming to initiate small wet loose avalanches on steep Southerly aspects. Warming may also cause slabs to be more reactive; something to keep in mind as we choose our late afternoon terrain.  


A wide angle view of Sunburst, Magnum, Cornbiscuit and Lipps – it may be March, but a generally thin snow cover remains

 

Weak layers in the snowpack at the mid-elevations on the South end of Seattle Ridge

 

Weather
Sun, March 4th, 2018

Overcast skies and snow flurries were over the region yesterday, with a trace of snow accumulating. Temperatures were in the upper 20’sF at 1,000′ and around 20F along ridgelines. Ridgetop winds were light and variable during the day before shifting Northwesterly overnight and picking up to the 5-10mph range. Temperatures also cooled to the teens overnight with colder air moving in.

Today, Sunday, we are expecting mostly sunny skies with light Northwest ridgetop winds (5-10mph). Temperatures are expected to rise to 30F at 1,000′ and to the mid-20’sF along ridgelines.  

Tomorrow, Monday, clouds move back in with another chance for snow flurries (little accumulation). The big news is later this week, a larger low-pressure system is forecast to move into the Gulf of Alaska. This could bring a much better chance for snowfall to the Turnagain area and Western Prince William Sound. Stay tuned!

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 28   trace   0   68  
Summit Lake (1400′) 18   0   0   28  
Alyeska Mid (1700′) 23   trace    0.02 60  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 16   W   6    21
Seattle Ridge (2400′) 20   NW   7     20  
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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