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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Mon, December 26th, 2016 - 7:00AM
Expires
Tue, December 27th, 2016 - 7:00AM
Forecaster
Aleph Johnston-Bloom
Avalanche risk The Bottom Line

A  BACKCOUNTRY AVALANCHE WARNING was issued through the National Weather Service yesterday  and remains in effect until 6 pm today  for the Turnagain Pass area and surrounding mountains.  

Heavy snowfall and strong winds have created a  HIGH avalanche danger  in the mountains surrounding Turnagain Pass, Girdwood Valley, Portage Valley and areas on the Kenai seeing heavy snowfall.  Dangerous avalanche conditions are expected on all slopes  30 degrees and steeper – including runout zones. Large avalanches are expected to release naturally, be easily triggered by people and could run to elevations below 1,000′.  

Travel in avalanche terrain is NOT recommended.  

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Mon, December 26th, 2016
Alpine
Above 2,500'
High (4)
Avalanche risk
Treeline
1,000'-2,500'
High (4)
Avalanche risk
Below Treeline
Below 1,000'
Considerable (3)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
High (4)
Treeline
1,000'-2,500'
Avalanche risk
High (4)
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

Yesterday natural avalanches 2 ft. deep were observed. These were long running and large enough to bury and kill a person. Cracking and collapsing (whumpfing) were also observed.

Red flags… Rapid loading = Expect dangerous avalanches.

STORM TOTALS in the upper elevations so far:

Turnagain Pass:     30+” and counting, 2.8″ of H2O
Girdwood Valley:    20+” and counting,  1.6″ of H2O
Summit Lake:         4-6″, .4″ of H2O

Snow continues to fall with another 1-4″ inches expected today.  16″- 20″ of snow was measured yesterday on Turngagain Pass. An additional 10+ inches has fallen since then. All of this new snow is forming thick slabs, especially in the alpine where consistent easterly winds have been blowing into the 40’s. The weak surface snow and weak snowpack have been rapidly loaded. Expect natural avalanches today and that triggering an avalanche is very likely on any slopes over 30 degrees. Avalanches have the potential to be long running and could be remotely triggered. Avoid travel underneath avalanche terrain as well. This includes the Seattle Ridge up-track and all slopes, gullies and runout zones. 

This needs to be highlighted again today:

Treed areas such as the Tincan Trees:  Storm snow slab avalanches 2-3′ thick are likely to be triggered in the trees. The new snow is denser than the underlying old snow – creating an upside down and unstable snowpack. Avoiding slopes over 30 degrees in treed areas is also recommended. Due to the weak faceted snow below the new snow the snowpack is “bottomless”. Movement through the snow was challenging yesterday and will only be more of a struggle today. 

Travel in avalanche terrain is NOT recommended. Deep, dangerous avalanches are likely. BE PATIENT. 

Natural avalanche in the Snake Pit on Tincan, 12.25.16. The next gully over also slid. 

Weather
Mon, December 26th, 2016

Yesterday skies were obscured and it snowed or rained depending on elevation throughout the day with periods of heavy precipitation. Easterly winds were in 20s gusting into the 40s. Temperatures were in the 20Fs at ridge tops and in 30s in the valleys. Rain/snowline fluctuated around 500′. The storm continued overnight and temperatures are rising slightly this am.  

Today will be cloudy and another 1-4″ of snow is forecasted to fall, rain below 400′. Temperatures are forecasted to hover around freezing, either above or below depending on elevation. Winds will remain easterly 5-15 mph with higher gusts in the alpine. The snow showers are forecasted to continue overnight into tomorrow with temperatures cooling and winds becoming calm.  

Tomorrow is forecasted to be cloudy with a slight chance of snow showers, temperatures in the low 20Fs and light NW winds.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 29    20  2  50 + (estimate)
Summit Lake (1400′)  31  2 .2    10
Alyeska Mid (1700′) 31    10  .9  32

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′) 24   rimed   rimed   rimed  
Observations
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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
Glacier District
Johnson Pass
Open
No parking in turnaround at end of the road near the outhouse.
Placer River
Open
Please do not ride along Railroad tracks. Cross tracks at 90 degree angle and clear the right of way.
Skookum Drainage
Closed
The Skookum Valley is closed to snowmachines. This closure occurs annually on April 1 as per the CNF Forest Plan.
Turnagain Pass
Open
Twentymile
Closed
Seward District
Carter Lake
Open
Lost Lake Trail
Open
Primrose Trail
Open
Resurrection Pass Trail
Closed
Closed for the 2020/21 winter season.
Snug Harbor
Open
South Fork Snow River Corridor
Open
Summit Lake
Open

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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.