Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sat, December 24th, 2016 - 7:00AM
Expires
Sun, December 25th, 2016 - 7:00AM
Forecaster
Aleph Johnston-Bloom
The Bottom Line

The avalanche danger is MODERATE this morning in the Alpine due to the possibility of fresh wind slabs on leeward aspects as winds have picked up and there is snow available for transport. At Treeline and below the danger is  LOW. The danger level may rise to CONSIDERABLE at all elevations  as a warm, wet and windy storm impacts the advisory area today. Watch for rapidly changing conditions, have a conservative mindset and adjust travel choices appropriately. Natural avalanches may be possible as the day progresses and human triggered likely.  

Check out the Summit Lake Summary HERE.  

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Sat, December 24th, 2016
Alpine
Above 2,500'
Considerable (3)
Avalanche risk
Treeline
1,000'-2,500'
Considerable (3)
Avalanche risk
Below Treeline
Below 1,000'
Considerable (3)
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
Considerable (3)
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

Soft settled snow will easily move as winds pick up in advance of the approaching storm. Wind slabs may be tender and easily triggered in the Alpine. As the snow starts today this will only become more likely. Wind speeds are forecasted to be easterly 25-45 mph gusting to 60 mph. Look for cracking, drifting and blowing snow. Cornices may also grow and become more tender with increasing wind, new snow and rising temperatures. 

 

Avalanche Problem 2
  • 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

As the snow starts to fall today it will land on very weak surface snow and is not expected to bond well. It is important to remember there is widespread surface hoar as well as small facets on almost surfaces from road level high into the alpine. Expect new snow to act as a slab fairly quickly due to this interface. As temperatures warm throughout the storm and the wind blows this may become even more pronounced. Rain or rain/snow mix falling on the old snow may produce avalanches as well at lower elevations. Look for red flags i.e. recent avalanches, cracking and collapsing (whumpfing). Pay attention to changing conditions!

 

Rimed surface hoar over soft settled (faceting) snow on Sunburst ridge. Photo: Kevan Dee

 

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

We have been tracking a couple of weak layers this season. Buried surface hoar from November 16th and December 15th have both produced avalanches. These layers are still buried in the snowpack in some terrain. In addition there is faceted surface snow and new surface hoar waiting to get buried. New snow load may cause avalanches that step down into old weak layers. This may not happen initially as the storm starts but should be a factor that is remembered as it progresses. We have a weak foundation/snowpack structure. Patience will be key in the next couple of days. We could see a large avalanche cycle if this storm really does it’s thing. 

Weather
Sat, December 24th, 2016

Yesterday was clear with some valley fog. Temperatures were inverted with single digits in the valleys and high teens at ridge tops. Winds were light. Last night the temperatures rose into the 20s and winds picked up this morning gusting into the 30s.  

Today there is a Winter Weather Advisory for the forecast area due to a warm wet storm that is forecasted to move into the region late this morning. Easterly winds will increase with gusting into the 60s and 3-7 inches of snow is expected today. Snow may be heavy at times and there is uncertainty with how warm it will be. Rain may fall below 1000′. The storm is forecasted to continue tonight into tomorrow with an additional 6-10 inches of snow overnight and 4-6″ tomorrow. The brunt of the storm is forecasted to be this evening.  

...WINTER WEATHER ADVISORY REMAINS IN EFFECT FROM NOON TODAY TO
9 AM AKST SUNDAY FOR TURNAGAIN PASS AND PORTAGE VALLEY...

* LOCATION...TURNAGAIN PASS AND PORTAGE VALLEY.

* SNOW...12 TO 19 INCHES FOR TURNAGAIN PASS. 8 TO 15 INCHES FOR
  PORTAGE VALLEY.

* VISIBILITY...ONE HALF MILE OR LESS AT TIMES.

* WIND...EAST WINDS 25 TO 45 MPH WITH GUSTS TO 60 MPH.

 Snow showers will continue into early next week with a clearing and cooling trend towards the weekend.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 15    0  0 24  
Summit Lake (1400′)  7  1  .1  8
Alyeska Mid (1700′)  16  0  0  16

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) Under repair      Under repair   Under repair     Under repair    
Seattle Ridge (2400′) 15    SE 21   27  
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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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