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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sun, December 11th, 2016 - 7:00AM
Expires
Mon, December 12th, 2016 - 7:00AM
Forecaster
Heather Thamm
The Bottom Line

A generally  LOW  avalanche danger exists across all elevations bands for the Turnagain Pass zone. Triggering a 1-2′ avalanche is unlikely but not impossible. The most suspect slopes are in steep terrain at the high elevations where someone just might be able to break off an old wind slab or find a slope with the buried surface hoar that hasn’t slid. Good travel habits, such as exposing one person at a time, watching your partners and grouping up in safe zones are key ways to minimize risk.  Ease onto steep slopes and be prepared to change your plans if an area becomes too crowded.

There is snow to sea level, just enough to put a LOW danger rating on the Below Treeline Elevation band. If venturing into the ‘periphery’ forecast zones, such as Girdwood Valley, more caution is advised due to limited information about the snowpack in these areas.  This should also be part of the equation if you are heading to ice climb in  Portage where even  a small slide could have high consequences.

If headed to Summit Lake check out the Saturday Summit Lake Summary  HERE.  

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Sun, December 11th, 2016
Alpine
Above 2,500'
Low (1)
Avalanche risk
Treeline
1,000'-2,500'
Low (1)
Avalanche risk
Below Treeline
Below 1,000'
Low (1)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Low (1)
Treeline
1,000'-2,500'
Avalanche risk
Low (1)
Below Treeline
Below 1,000'
Avalanche risk
Low (1)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Normal Caution
    Normal Caution
Normal Caution
Normal Caution means triggering an avalanche is unlikely but not impossible.
More info at Avalanche.org

Remember LOW hazard doesn’t mean NO hazard! Yesterday lots of slope tester were observed and there were no human triggered avalanches reported. With a stable weather pattern dominating our region and very little changes affecting the snowpack we are in a Normal Caution phase for avalanche issues. These include:

1- Triggering an outlier avalanche. This would most likely be an ‘unsupported slab’ that sits above a cliff or steep rocky terrain. More on this below in ‘Additional Concerns.’

2- Triggering an old wind slab – Avoid hard stiff snow sitting in steep rocky terrain where a small isolated wind slab could have high consiquences.  

3- Triggering a cornice fall. Cornices maybe be small right now, but similar to wind slabs they could take you down somewhere you don’t want to go. Give cornices a wide berth.

4- Sluffs on steep slopes. Small sluffs were observed yesterday, and as the surface snow becomes weaker under clear skies the potential for bigger stuff will increase. 

Thin snow cover, limited access and high volumes of people will add another degree of challenge for making safe decisions. Before commiting to a route in steep avalanche terrain ensure that you are only exposing one person at a time. In places where you can not see the entire slope this may not be possible. Be prepared to change your objectives if an area becomes too crowded to manage.

An example of the crowds from yesterday, 15 people on the skin track on a SW aspect of Magnum. 

 

Additional Concern
  • Persistent Slabs
    Persistent Slabs
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
More info at Avalanche.org

Even with LOW avalanche danger it is still important to remember the weak layer 1-2′ below the surface i.e. the notorious Nov 16th buried surface hoar. Although we have not seen an avalanche release in this layer since last Saturday and the slab character has been changing due to the cold temperatures, there are many slopes away from the ‘popular’ zones that have yet to be tested. These are the areas most suspect over the weekend. Finding the spot that harbors this weak layer, still has a slab, and hasn’t been skied or slid already still could be dangerous… Triggering is unlikely but not impossible!

Weather
Sun, December 11th, 2016

Yesterday skies were clear with thick valley fog rolling in/out of Turnagain Arm. Temperatures were near zero (F) at lower elevations and in the alpine temperatures average around 15F. Winds were light and variable and no precipitation was recorded.  

Today looks very similar with slightly warmer temperatures, 15F-25F with a slight temperature inversion in the alpine. Winds are expected to remain light from the NW and no precipitation is expected.

Cold arctic air sitting over mainland, Alaska will continues to dominate our weather pattern over the next few days. The next chance for a pattern change/possibility of precipitation will be later in the week.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 15   0   0   21  
Summit Lake (1400′) 3   0   0   4  
Alyeska Mid (1700′) 16   0   0   10  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 19   Var.   6   17  
Seattle Ridge (2400′) 18   Var.   4   20  
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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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