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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Mon, November 26th, 2018 - 7:00AM
Expires
Tue, November 27th, 2018 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

Continued snowfall and wind above 2,500′ will keep the avalanche danger at HIGH in the Alpine. Storm snow avalanches are expected again today at these upper elevations. At the mid-mountain elevations, rain falling up to 2,500′ will continue to wash away the snowpack and initiate wet avalanches on steep slopes where enough snow still exists.  The avalanche danger remains  CONSIDERABLE  in the treeline band as avalanches from above may run into these mid-elevations.  Travel above treeline is NOT recommended.

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Mon, November 26th, 2018
Alpine
Above 2,500'
High (4)
Avalanche risk
Treeline
1,000'-2,500'
Considerable (3)
Avalanche risk
Below Treeline
Below 1,000'
No Rating (0)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
High (4)
Treeline
1,000'-2,500'
Avalanche risk
Considerable (3)
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
  • Storm Slabs
    Storm Slabs
  • Almost Certain
    Very Likely
    Likely
    Possible
    Unlikely
    Likelihood
  • Historic
    Very Large
    Large
    Small
    Size
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.

Likelihood of Avalanches
Terms such as "unlikely", "likely", and "certain" are used to define the scale, with the chance of triggering or observing avalanches increasing as we move up the scale. For our purposes, "Unlikely" means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. "Certain" means that humans will be able to trigger avalanches on many slopes, and natural avalanches are expected.

Size of Avalanches
Avalanche size is defined by the largest potential avalanche, or expected range of sizes related to the problem in question. Assigned size is a qualitative estimate based on the destructive classification system and requires specialists to estimate the harm avalanches may cause to hypothetical objects located in the avalanche track (AAA 2016, CAA 2014). Under this schema, "Small" avalanches are not large enough to bury humans and are relatively harmless unless they carry people over cliffs or through trees or rocks. Moving up the scale, avalanches become "Large" enough to bury, injure, or kill people. "Very Large" avalanches may bury or destroy vehicles or houses, and "Historic" avalanches are massive events capable of altering the landscape.

Signal Word Size (D scale) Simple Descriptor
Small 1 Unlikely to bury a person
Large 2 Can bury a person
Very Large 3 Can destroy a house
Historic 4 & 5 Can destroy part or all of a village
More info at Avalanche.org

Today we should see the third pulse in a series of warm storms impact the region. Temperatures climbed to 32F at 2,500′ yesterday, bringing rain as high as 2,200′. Today those numbers are expected to increase. Another 0.5″ of rain up to 2,500′ is forecast with 0.7″ tonight. In the alpine (above 2,500′) an additional 6-8″ of snow should fall today and 8-10″ tonight. Snow will be accompanied with winds in the 30’s and 40’s along the ridgetops from the east.

It is unknown the extent of the avalanche activity yesterday at the upper elevations due to limited visibility, but we did get a photo sent in to us of wet loose avalanches on the west face of Magnum at Turnagain Pass (thank you!). These avalanches were due to rain on snow, which will be expected again today. Obscured in the clouds at the high elevations we are expecting storm snow avalanche activity to continue. The new snow is piling up on a slick hard surface left from last week – which was a hard crust likely topped with surface hoar. This set up should be producing slab avalanches and as soon as the clouds part we’ll be doing our best to take stock. 

Storm totals at the mid-elevation snow stations for this soggy storm cycle:

  • Girdwood Valley at 1,700′:  4″ wet snow, 2,4″ of water equivalent (mostly in the form of rain)
  • Turnagain Pass at 1,880′:  16″ wet snow, 2.2″ of water equivalent (also seeing some rain)
  • Summit Lake at 1,400′:  2″ wet snow, 0.5″ of water equivalent (also seeing rain)

State of the snowpack? Although the snowpack is thickening in the high mountain terrain we are loosing the little snow that was there at the mid-elevations. Before this storm there was roughly 2-3′ of snow depth at 3,300′, that should be close to doubling after today’s snowfall. At 2,200′ and getting higher … bare ground is taking over as rain is washing away the few inches of snow remaining. 

 

Hard to see, but there are wet loose point release avalanches on the west face of Magnum, seen from the Center Ridge trail (Photo: Jacob Swartz).

Weather
Mon, November 26th, 2018

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 35   3″ wet snow (with some rain) 1.2 15  
Summit Lake (1400′) 35   1   0.3   0  
Alyeska Mid (1700′) 35   Rain   1.9   0  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 28   NE   27   75  
Seattle Ridge (2400′) 32   SE   20    57
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Riding Areas
Updated Fri, May 01st, 2020

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
Placer River
Closed
Skookum Drainage
Closed
Turnagain Pass
Closed
Closed as of May 1. Thanks for a fun, safe season!
Twentymile
Closed
Seward District
Carter Lake
Closed
Lost Lake Trail
Closed
Primrose Trail
Closed
Resurrection Pass Trail
Closed
Snug Harbor
Closed
South Fork Snow River Corridor
Closed
Summit Lake
Closed

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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.