Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Fri, December 11th, 2015 - 7:00AM
Expires
Sat, December 12th, 2015 - 7:00AM
Forecaster
Heather Thamm
The Bottom Line

Today a CONSIDERABLE avalanche danger exists in the Alpine and at Treeline.  Triggering a slab 2-3′ thick will be likely in steep terrain as additional loading will be adding stress to the snowpack.  If venturing into the mountains cautious route-finding and conservative decision-making are essential.

*On the Southern end of Turnagain Pass and near Summit Lake, slab depths are shallower, but triggering a slab 1-2′ thick is likely in avalanche terrain.

Below Treeline a MODERATE avalanche danger exists where an avalanche from above in steep channeled terrain is unlikely, but possible.

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Fri, December 11th, 2015
Alpine
Above 2,500'
Considerable (3)
Avalanche risk
Treeline
1,000'-2,500'
Considerable (3)
Avalanche risk
Below Treeline
Below 1,000'
Moderate (2)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Considerable (3)
Treeline
1,000'-2,500'
Avalanche risk
Considerable (3)
Below Treeline
Below 1,000'
Avalanche risk
Moderate (2)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
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.
More info at Avalanche.org

This morning snow showers combined with moderate winds are expected to bring another 5-7” of new snow to an already precarious snowpack. Yesterday 20″ of unconsolidated new snow was observed above 2000′ on Tincan Mountain. Unfortunately the additional snow today might not be enough to tip the balance naturally. However triggering a slab up to 3’ thick should be at the forefront of our minds as Easterly winds, 20-30mph will be transporting snow and creating more of a cohesive slab.

 

 

 

Yesterday’s Mid Elevation Storm Totals:

  • Girdwood ~9”
  • Northside of Turnigain ~13”
  • Southside of Turnigain ~3”
  • Summit Lake: ~3”

This set up will likely be more dangerous in the Alpine of Girdwood and the Northern side of Turnagain Pass where snow totals yesterday were much deeper. This does not mean triggering an avalanche in a shallower snowpack will be any less likely.Yesterday a D-2, natural slab avalanche was reported in Summit Lake on Butch Mountain and poor structure exists in all areas of our forecast zone. Pay attention for wind loading, shooting cracks, and “wumpfing” if you decide to go into the mountains. Avoiding avalanche terrain is recommended as more snow is expected to fall through out the weekend. Give this snowpack time to adjust and avoid slopes angles over 35°. 

Its always important to watch for deteriorating conditions. Should snowfall become intense or winds become stronger than forecasted, avalanche danger could increase beyond a CONSIDERABLE danger rating. 

Yesterday Tincan recieved an unexpected 20″ of new snow compared to smaller amounts on the Sourthern end of Turnagain Pass

Avalanche Problem 2
  • 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

It’s important to note the current snowpack structure we are dealing with. A persistent weak layer of faceted snow is sitting on a firm bed-surface below yesterday’s storm totals. Observations yesterday confirm that this new snow was warm and wet below 1500’, but in the upper elevations it was dryer and unconsolidated. As this new snow begins to settle it will likely become more cohesive and “slab like” in the upper elevations. Additional loading due to wind and new snow will increase this process over the next few days. Warm temperatures can also cause a slab to become more cohesive. The scary part about this current set-up is that incremental loading will likely not tip the balance, leaving the slopes primed for a human trigger. The current forecast for today is an additional 5-7” of new snow and more snow forecasted through the weekend. Patience and avoiding avalanche terrain will be the key to not triggering an avalanche while this snowpack adjusts to its new load. 

 

Weather
Fri, December 11th, 2015

Yesterday 20 € of new snow was observed in the upper elevations of Turnagain Pass. This snow favored the Northern side of the pass and arrived with warm temperatures. Rain/snow line was around 1000′ leaving heavy wet snow along the Turnagain Pass road corridor. Winds were light to moderate from the NE.

Overnight skies cleared and temperatures dropped into the upper 20F’s. No new snow was recorded overnight and winds were light 10-15mph from the Northeast.

5-7 € of new snow is expected to arrive late morning. Easterly winds have already picked up this morning and will remain moderate, 15-30mph with Gusts in the 40 through early evening. Temps will be slightly cooler today with rain/snow line estimated for about 500′.

Snow showers and moderate winds are expected throughout the weekend.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 29F   3   0.3   36  
Summit Lake (1400′) 27F   1   0.1    12
Alyeska Mid (1700′) 30F   1   0.08    25

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 23F   NE   14   46  
Seattle Ridge (2400′) 25F   E   11   25  
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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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