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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Thu, December 4th, 2014 - 7:00AM
Expires
Fri, December 5th, 2014 - 7:00AM
Forecaster
Wendy Wagner
Avalanche risk The Bottom Line

The avalanche danger is expected to rise to MODERATE today in the Alpine terrain as 3-5″ of new snow is forecast accompanied by moderate Easterly winds. In areas with new snow and wind, fresh wind slabs 6-10″ in depth will be possible to trigger on leeward slopes off ridgelines and other exposed terrain features. Loose snow sluffs on steep slopes should also be expected in areas seeing new snow. A continued lack of snow cover below treeline results in No Rating at this low elevation.

In the event only a trace of new snow falls, watch for old wind slabs in steep exposed terrain. Otherwise, triggering an avalanche will be unlikely.

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Thu, December 4th, 2014
Alpine
Above 2,500'
Moderate (2)
Avalanche risk
Treeline
1,000'-2,500'
Low (1)
Avalanche risk
Below Treeline
Below 1,000'
No Rating (0)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Moderate (2)
Treeline
1,000'-2,500'
Avalanche risk
Low (1)
Below Treeline
Below 1,000'
Avalanche risk
No Rating (0)
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

There is uncertainty as to how much new snow the Eastern Turnagain Arm will see today. Likely, some areas will get several inches while a couple ridgelines over may see only a trace. In areas seeing several inches or more of new snow, fresh wind slab avalanches will be the main concern. The winds are forecast to average between 15-25mph, which are ideal wind loading speeds. The Seattle Ridge weather station is reading in this range this morning while the Sunburst weather station is quieter (~10mph) with speeds increasing through the day.

The good news is, the warm temperatures (mid 20’s F) above treeline will help to stabilize the new snow relatively quickly. Your best bet at triggering an avalanche is to step on a very fresh wind loaded slope. Watch for wind loading in action and areas where the snow is more cohesive and cracking around you. These slabs should be in the 5-10″ range and fairly soft.

Below is a look at yesterday’s surface. This area, in the Summit Lake region, is quite wind affected, however many areas still harbor soft settled powder.    
                 

Avalanche Problem 2
  • Dry Loose
    Dry Loose
Dry Loose
Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.
More info at Avalanche.org

Dry snow sluffs at the upper elevations are possible while wet, or moist, snow sluffs are possible near treeline. Temperatures look to climb to 32F near treeline, which will moisten any new snow that falls. These should be low volume and something to keep in mind on steep slopes over 40 degrees.

Weather
Thu, December 4th, 2014

Weather yesterday was mostly cloudy with light to moderate Easterly winds. A trace of snow was picked up at Turnagain Pass with the rain/snow line near sea level. Overnight, temperatures have warmed a few degrees to the mid 20’sF on the ridgetops and 30F at treeline. This is associated with a large scale Southeasterly flow that is pumping warm air our way from the South.  

Today, we are expecting a pulse of moisture embedded in the Southerly flow to add 3-5″ of new snow with slightly warming temperatures (up to 32F at treeline and the upper 20’sF on the ridgetops). Rain (and maybe a rain/snow mix) is expected at sea level. Winds should remain 15-25mph from the East.

This general pattern is expected to continue into the weekend with off-and-on snow showers above 1,000′ and rain below – amounts of snow are uncertain but look to be only a few inches here and there. We could see a break in cloud cover and precipitation tomorrow, Friday.

                     

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 28   1   0.1   19  
Summit Lake (1400′) 24   0   0   5  
Alyeska Mid (1700′) 29   1   0.1   17  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 21   E   10   30  
Seattle Ridge (2400′) 24   NE   15   26  
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Riding Areas
Updated Tue, April 20th, 2021

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
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No parking in turnaround at end of the road near the outhouse.
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Open
Please do not ride along Railroad tracks. Cross tracks at 90 degree angle and clear the right of way.
Skookum Drainage
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The Skookum Valley is closed to snowmachines. This closure occurs annually on April 1 as per the CNF Forest Plan.
Turnagain Pass
Open
Twentymile
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Closed for the 2020/21 winter season.
Snug Harbor
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Summit Lake
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This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area. This advisory does not apply to highways, railroads or operating ski areas.