Turnagain Pass Avalanche Forecast RSS

Archives
ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Tue, December 5th, 2017 - 7:00AM
Expires
Wed, December 6th, 2017 - 7:00AM
Forecaster
Aleph Johnston-Bloom
The Bottom Line

The avalanche danger is  CONSIDERABLE  at all elevations today. Triggering a slab 2-3+ feet thick will be likely on slopes steeper than 30 degrees and natural avalanches are possible as the next storm system moves into the region. Cautious route-finding and conservative decision-making are essential today. Pay attention to changing conditions. If today’s storm is more intense than forecasted the danger will bump back up to HIGH.  

Below 1,000′ where predominantly rain is falling, debris running into these lower elevations from avalanches remains possible along with wet loose avalanches on steep slopes.  

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Tue, December 5th, 2017
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
  • 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

The advisory area continues to be in an unsettled weather pattern. Snowfall, rain and wind will continue to add stress to the snowpack. Yesterday was a lull in intensity after 2-3′ of snow (2-3″ of rain at sea level) fell and winds gusted over 100mph on Saturday. There was evidence of an avalanche cycle during the storm observed yesterday. This was not quite as widespread as expected which leaves many slopes suspect and human triggered avalanches likely and additional natural avalanches possible. An example illustrating this point is that avalanche hazard mitigation in the Girdwood Valley yesterday produced avalanches running to ground on slopes adjacent to natural avalanches that had run in the storm. Translation: slopes that haven’t slid could be hanging in the balance waiting for a trigger. Don’t be that trigger. It might not be the 1st person on the slope. The slab depth has increased over the weak faceted snow. Remember the facets were very reactive prior to the storm. Staying off of slopes steeper than 30 degrees and avoiding runout zones will be important today. A small slide into a terrain trap could be consequential.  Additional snow and rain are forecasted to fall and winds could move snow at upper elevations increasing the load today.  This snowpack will need time to adjust. Be patient and be on the lookout for recent avalanches, cracking and collapsing, signs that the snowpack unstable. 

Natural avalanches on Sunburst that occurred during the storm Saturday.

 

Small avalanches and wind effect in along Seattle Ridge. 

 

Avalanche Problem 2
  • 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

Very high winds during the storm Saturday have loaded leeward slopes. In addition there is snow falling today and winds gusting into the 40s. Winds slabs are likely found along ridgelines as well as lower down slopes due to those high wind speeds on Saturday. Pay attention to cracking and hollow sounding snow. Wind slabs could be soft or hard depending on exposure to winds and if triggered could release a larger persistent slab lower down on the slope. Today is not the time to be pushing into steep terrain. Avoiding slopes greater than 30 degrees is recommended.

Wind loading on leeward slopes, Tincan.

Weather
Tue, December 5th, 2017

Yesterday was overcast with light rain and snow showers on and off throughout the day. Winds were easterly 15-25 mph with gusts as high as 60 mph. Upper elevations picked up an additional 2-5″ of snow and rain fell to around 1500′. Temperatures were as high as 40F at sea level and the mid to high 20s at upper elevations.  

Today will be mostly cloudy with .4″ of water (4-6″ snow) forecasted to fall. Today will start warmer and cool a bit this morning bringing the snow level down. Winds will be easterly 10-20 mph gusting into the 40s.Tonight into tomorrow a stronger wave of precipitation is forecasted to impact the area. The model runs on this are still uncertain this morning, however looking into the future NWS says “Much more confidence exists in the forecast for  Southcentral to remain well above normal for temperatures, and  continue to deal with round after round of moisture from the  subtropical Pacific.  Stay tuned!  

*Center Ridge SNOTEL is reporting erroneous temperature data. See  Turnagain Pass DOT weather station  for accurate temperature at 1000′.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 32*    0  .2 29  
Summit Lake (1400′) 33   0  .3  9
Alyeska Mid (1700′) 34   0  .2  18

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  24  ENE  26 60  
Seattle Ridge (2400′)  28  ESE    18 40
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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