Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Fri, March 31st, 2017 - 7:00AM
Expires
Sat, April 1st, 2017 - 7:00AM
Forecaster
Aleph Johnston-Bloom
The Bottom Line

Snowfall, rain and strong winds are creating a  HIGH  avalanche danger at all elevations in Turnagain Pass,  Portage, Placer and Girdwood Valley where natural avalanches 2-3′ thick are likely today.  Travel is not recommended in avalanche terrain where natural avalanches are likely occurring due to rapid loading. Steer clear of gullies and the bottom of large and steep slopes in the event an avalanche occurs above you.

Hiking in Portage Valley:  Travel along, and past, the designated Byron Glacier trail is not recommended due to exposure to avalanche terrain. Natural avalanches are possible today that could send debris to valley floors.

Summit Lake:  The storm cycle brought 6-10″ of new snow and gusty winds. Read the  Saturday Summit Summary  HERE  and an observation from yesterday HERE.  

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Fri, March 31st, 2017
Alpine
Above 2,500'
High (4)
Avalanche risk
Treeline
1,000'-2,500'
High (4)
Avalanche risk
Below Treeline
Below 1,000'
High (4)
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
High (4)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Storm Slabs
    Storm Slabs
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.
More info at Avalanche.org

New snow and wind have combined to create very unstable slabs, 2-3’ thick. 6-12″ of snow fell in the last 24 hrs adding to the previous storm totals. Ridgetop winds from the East (SE to NE) picked up yesterday into the 30s and 40s mph and continued with several gusts in the 70s overnight at Sunburst weather station. Sustained winds are forecasted to continue today. Fresh cornices could fall and wind slabs will be found in leeward terrain. Rain started falling at lower elevations and rain/snow line is expected to rise to 2000′ today. An additional 6” of snow is forecasted for the higher elevations today.  Slabs will likely release naturally in steep terrain and could step down into older layers in some locations. Natural avalanches could run the full length of a slope, thus it will be extra important to avoid being near any runout zones today. Human triggered avalanches are likely.  An observer yesterday reported very touchy conditions in the Tincan trees. Storm slabs in areas protected from the wind continue to be a concern. Remember that prior to the storm starting Tuesday, the snow surface was surface hoar and/or near surface facets or a sun crust, not layers that new snow bonds well with. This is not a complicated situation.  Avoidance of avalanche terrain is the only way to “manage” the avalanche hazard today. 

New snow in Summit Lake not bonding to the surface hoar buried below.  Remember the Turnagain Advisory area has 2-3′ of snow on this same set-up. Photo: Conrad Chapman

 Turnagain motorized lot yesterday, Poor visibility due to snowfall and sustained winds. Photo: Conrad Chapman

Avalanche Problem 2
  • Wet Loose
    Wet Loose
Wet Loose
Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
More info at Avalanche.org

Rain falling on snow to 2,000’ will weaken the surface snow and possibly an older layer beneath. Temperatures are forecasted to rise to 40F at lower elevations today. Wet loose avalanches are likely and wet slab avalanches are possible due to a layer of buried surface hoar and/or near surface facets 2-3’ below the surface. In channeled terrain an avalanche from above will likely entrain weak snow in the lower elevations increasing overall volume. Triggering a wet avalanche in the lower elevations could have high consequences if pushed into or over terrain traps such as cliffs, gullies, or trees. Again it will be important to avoid steep terrain and maintain a conservative distance from all runout zones.  

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

Don’t forget that our snowpack harbors several old layers of weak snow. Avalanches releasing in the storm snow have the potential to ‘step down’ into these layers. Furthermore, as the new snow piles up and begins to stick to the old snow surface, avalanches breaking into them is possible as the load increases. Both of these situations can create a much larger avalanche – something to keep in mind as the storm cycle continues into the weekend. 

 

Weather
Fri, March 31st, 2017

Yesterday was stormy with SE-NE winds gusting into the 50s and snow falling throughout the day, a foot on Turnagain Pass and 6-8″ in Girdwood. Temperatures were in the 20Fs to low 30Fs.

Overnight winds increased with gusts into the 70s. Temperatures rose into the mid 30s and are slowly climbing this morning. Rain started falling at lower elevations. Today rain/snowline is forecasted to rise to 2000′ as warm air pushes into the region. Up to an additional 6″ of snow could fall today at higher elevations. Winds will continue from the SE-NE 20-30 mph with gusts into the 50s. Precipitation will continue tonight into tomorrow.  

The active weather pattern will continue into next week as a series of lows move into the Gulf.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 30   9   .9   78  
Summit Lake (1400′) 30 2   .2 34  
Alyeska Mid (1700′) 29 8 .5   80

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  20 ENE   35    80
Seattle Ridge (2400′) 23   SE 30    51  
Observations
Recent Observations for Turnagain Pass
Date Region Location
12/10/19 Turnagain Avalanche: Tincan and Sunburst from the air
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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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