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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Thu, November 29th, 2018 - 7:00AM
Expires
Fri, November 30th, 2018 - 7:00AM
Forecaster
Heather Thamm
The Bottom Line

The avalanche danger is  MODERATE  in the Alpine where triggering a slab avalanche is possible on all aspects. Below 2500′ the danger is  LOW where freezing temperature are helping a thin and wet snowpack form a crust.  

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Thu, November 29th, 2018
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
  • 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
This graphic depicts how likely you are to trigger avalanches or encounter natural avalanches while traveling on avalanche prone slopes. Unlikely means that few avalanches could be triggered in avalanche terrain and natural avalanches are not expected. The chance of triggering or observing avalanches increases as we move up the scale. Certain means that humans will be able to trigger avalanches on many slopes, and natural avalanches should be expected.

Size of Avalanches
This graphic depicts the potential size and destructive force of expected avalanches. 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, large enough to bury or destroy vehicles and break a few trees, and large enough to destroy railway cars, buildings, or a substantial amount of forest. Historic avalanches are massive events capable of destroying villages and gouging or altering the landscape.
More info at Avalanche.org

Last night was the first freeze in five days since a series of warm and wet storms ended yesterday morning.  Not much snow exists below 2000′ due to heavy rain that may have reached ridgetops at times. We don’t have a lot of information from the upper elevations, above 2500’, at this point. We know 4+’ of snow fell over a four-day period and strong Easterly winds have loaded leeward features and cross-loaded other aspects. Prior to this storm a melt-freeze crust and surface hoar formed in the upper elevations. We don’t know how much avalanche activity occurred during the storm and if this poor structure is lingering in places that haven’t avalanched.

Today triggering an avalanche is possible in the Alpine and could be large enough to bury a person. If you hike into the Alpine where there is enough snow to slide ease into avalanche terrain with a cautious mindset. We are still in the 48-hour period since heavy snow and strong winds formed storm slabs. Avoid avalanche terrain if you observe any signs of instability: recent avalanches, shooting cracks, or whumpfing

Webcam pictures from DOT weather station provided our first glimpse into the Alpine yesterday afternoon – Northern and Western aspects of Tincan above 2000′. 

 

 

Brief clearing in the afternoon provided a nice glimpse of an Eastern aspect of Seattle Ridge. Note how little snow exists in the lower elevations.

 

 

West aspect of Butch in foreground and Northern aspects of Tenderfoot and Tri-Tip in the background. Photo from Mon Nov. 26  at Lower Summit Lake.

Weather
Thu, November 29th, 2018

Yesterday: Moderate Easterly ridgetop winds diminished yesterday morning becoming light by early evening. Skies were obscure most of the day a broken period late afternoon. Temperatures dropped below freezing last night allowing 0.1 € of snow water equivalent to fall as an inch of snow to sea level from Girdwood to Turnagain Pass last night.

Today: Scattered snow showers and a trace of snow are possible this morning with clearing skies in the forecast this afternoon. In the upper elevations temps will average in the low 20Fs and upper 20Fs near sea level.   Winds will remain light and variable.

Tomorrow: Temperatures will start to increase as another storm moves into our region Friday into Saturday. This storm will have a Southwesterly flow, which typically favors Hatcher Pass for precipitation. Temperatures are expected to reach above freezing and rain is likely in the mid and lower elevations. Increasing temps and winds are expected in the Western Chugach and Kenai Mountain.

 *Seattle Ridge weather station stopped collecting wind data at 10 pm on Nov 27, 2018.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 29    1″ 0.1   10  
Summit Lake (1400′) 27   0   0   0  
Alyeska Mid (1700′) 30   1″ 0.16   *N/A  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 21   ENE   5   27  
Seattle Ridge (2400′) 26   *N/A   *N/A     *N/A    
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Riding Areas
Updated Mon, December 02nd, 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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