Turnagain Pass Avalanche Forecast RSS

Archives
ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Fri, January 1st, 2016 - 7:00AM
Expires
Sat, January 2nd, 2016 - 7:00AM
Forecaster
Aleph Johnston-Bloom
The Bottom Line

A  CONSIDERABLE  avalanche danger exists both at Treeline and in the Alpine where human triggered  windslabs 1-4′ thick are likely on steep wind loaded features. The storm coming in today will bring new snow, rain and wind adding load and building sensitive storm slabs. Natural avalanches will be possible. Cautious route-finding and conservative terrain choices will be important.  Conditions may change rapidly in the afternoon into the evening, when the precipitation instensity is forecasted to be the heaviest.  

A  MODERATE  avalanche danger exists below 1000′ where a larger avalanche from above could run into this elevation band.

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Fri, January 1st, 2016
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
  • 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

After a break in the stormy weather for most of the day yesterday we are back in it today. The first storm of 2016 could bring another 2 inches of moisture to the advisory area today and tonight as well as ramping up the winds. Rain/snow line is forecasted to be around 1800′ again. There will be a variety of storm snow concerns today. Look for signs of instability while traveling: recent avalanches, cracking and whumpfing are all indications that the snowpack is becoming stressed. As always use safe travel protocols and don’t linger in runout zones. 

1) Storm slab: As the new snow falls today it may not initially bond to the existing snow surface and/or be wetter and heavier. This could create sensitive slabs in much of the terrain.

2) Wind slab: Triggering a wind slab 1-4’ thick is likely on steep wind loaded features where multiple layers of wind affected snow exist. Yesterday these wind loaded areas were easy to spot due to their pillow-like shape, but today another 10” of snow is expected and Easterly winds 30-50 mph will be transporting more new snow on top, thus adding additional stress to the snowpack and the potential for more wind slabs.

3) Cornices: With such strong winds and warm snow at ridgetops, we can expect cornices to be tender. These ‘backcountry bombs’ are likely to trigger a wind slab or step down to a deeper instability. Avoid ridgelines with large cornices and don’t put yourself below one.

4) Wet loose avalanches: More rain on snow will saturate the upper layers of the snowpack below 1800’. This is more of a concern in areas with terrain traps and in steep channeled terrain where an avalanche from above will be impossible to escape. 

Wind effected snow in Hippy Bowl yesterday: cornices, wind-pillows and sculpted ridgelines will all change with the additional snow and wind today. 

 

Avalanche Problem 2
  • Deep Persistent Slabs
    Deep Persistent Slabs
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
More info at Avalanche.org

The Thanksgiving Rain Crust (TRC)/small facet combo is getting more and more deeply buried but continues to be on our radar as a concern. Yesterday we received additional reports of avalanches breaking into older weak snow primarily in the periphery of our advisory area. As the snowpack gets yet another load we will be monitoring whether slides are breaking in old snow on this persistent weak layer. Cautious travel is already advised. Deep slab potential is another reason to not put more than one skier/rider or sledder on the slope in avalanche terrain and to watch out for thin spots where triggering may be easier. 

Pit from Tincan 2300′, SW aspect. Note: facets over the TRC buried over 3′ deep.

 

Weather
Fri, January 1st, 2016

Yesterday skies mostly cleared after a burst of precipitation favoring the Girdwood Valley in the early morning. Temperatures were in the mid 20Fs at ridgeline and warmer in the valleys. Winds were easterly and blew 10-20 mph throughout the day.

Clouds increased overnight as the next storm moved into the region. Today will be overcast with rain/snow falling. 5-10 inches of snow is forecasted for the mountains today. Rain/snow line should be approximately 1800′. Easterly winds will increase to 30-50 mph this afternoon. Temperatures will be in the high 20Fs-mid 30Fs. The storm will continue overnight with an additional 3-12 inches of snow forecasted to fall. The rain/snow line will be dropping as temperatures cool slightly.  

Rain/snow showers will continue through the weekend as the active pattern persists. The series of Low pressure systems continue to move into the Gulf in conjuntion with a moisture plume being pushed over the area by the jet.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 30    1 .1   71  
Summit Lake (1400′)  32  0  0 18  
Alyeska Mid (1700′)  31 4.5 .54   59  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 23   ENE    20 52  
Seattle Ridge (2400′) 25  n/a n/a   n/a  
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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