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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Fri, January 13th, 2017 - 7:00AM
Expires
Sat, January 14th, 2017 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

The avalanche danger is expected to rise to  CONSIDERABLE  by the end of the day on upper elevation slopes receiving over 8″ of new snow accompanied by strong wind. In this case, wind slabs 10-16″ thick are likely to be triggered by people on leeward slopes and may release naturally. In areas unaffected by winds and receiving less snow (4-6″ ish) the danger will be MODERATE  where small shallow storm slabs and sluffs in the new snow may be triggered on the steeper slopes.  

*Today’s avalanche danger is dependent upon how much snow this storm produces.

Ice climbers and hikers:  In Portage Valley and other areas where climbing routes and trails sit under avalanche paths, be aware that debris from a naturally occurring slide above may run to these lower elevations.

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Fri, January 13th, 2017
Alpine
Above 2,500'
Considerable (3)
Avalanche risk
Treeline
1,000'-2,500'
Moderate (2)
Avalanche risk
Below Treeline
Below 1,000'
Moderate (2)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Considerable (3)
Treeline
1,000'-2,500'
Avalanche risk
Moderate (2)
Below Treeline
Below 1,000'
Avalanche risk
Moderate (2)
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

It’s official – after a two-week dry spell, snow is falling this morning!! Although there’s only been around an inch so far, by this evening we could get up to 8-10″ in favored locations and 4-6″ in un-favored locations. Plus, an additional 4-6″ is possible overnight tonight. It will be one of those days to keep close tabs on how much new snow has fallen and how hard is it snowing. This will directly influence the avalanche hazard. The new snow is falling on a variety of old surfaces, including slick hard wind slabs/crust and soft faceted snow. Despite the myriad of different surfaces, expect bonding of the new snow to initially be poor.

Upper-elevation slopes in the Alpine are likely to be obscured today, but this is the terrain most suspect for receiving enough snow (up to 8+”) along with winds strong enough to form wind slabs that release naturally. If you find yourself in this situation, expert level snowpack assessment is necessary for entering avalanche terrain. Mid-elevation slopes and areas in the trees are more likely to receive less snow (4-6″) and little wind. In this terrain, naturally occurring avalanches are unlikely but human triggered shallow soft slabs and sluffs, the depth of the new snow, may be possible on the steeper slopes. 

What to watch for:

  1. How much new snow are you traveling through?
  2. Heavy snowfall, strong winds?
  3. Cracking in the new snow?
  4. Are you traveling under an avalanche path that may be loading with snow above you?

Stepping off the skin track or jumping off your snowmachine to do quick hand pits will be a great tool for sussing out new snow depth and bonding. If skies are clear enough, look for loose snow avalanches in the steep terrain and keep your situational awareness up as the day progresses! 

Photo below: An example of the pre-existing snow surface that the new snow is falling on – old hard wind slabs/crusts. Very weak faceted snow sits under these hard slabs and crusts. Once the storm snow bonds with the crust we could see avalanches breaking in the faceted snow beneath (will we get enough of a load for this? a focused question for this weekend).
 

Additional Concern
  • Glide Avalanches
    Glide Avalanches
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
More info at Avalanche.org

Warming temperatures associated with the Southerly flow may enhance glide activity. Glide cracks have been slowing opening this week; though we have not seen/heard of any new cracks releasing. Keep an eye out for cracks, which is difficult with new snow and wind, and limit time underneath them.

Weather
Fri, January 13th, 2017

Yesterday was our last clear sky day with temperatures in the single digits in valley bottoms and the teens-20’s in the upper elevations. Ridgetop winds picked up later in the day from the Southeast to the 10mph range.

Overnight, clouds filled in and light snowfall began around 3-4am. Roughly a trace to an inch is being reported at stations this morning, including snow to sea level. Ridgetop winds have bumped up to 15-20mph with gusts into the 30’s. Temperatures have climbed dramatically at sea level as the inversion has been scoured away (28-30F at sea level, mid-20’s at the mid-elevations and mid-teens at the Ridgetops).

Today, we are expecting anywhere from 4-8+” of new snow and another 4-6″ tonight. Although temperatures have warmed dramatically, we should still see mostly snow to sea level with this event. Ridgetop temperatures will be in the mid-20’s F. Ridgetop winds are likely to increase more today into the 20-40mph range with gusts into the 50’s.

Tomorrow the system looks to move out and skies begin to break up as a cold and dryer North flow heads our way.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 21   trace   0   33  
Summit Lake (1400′) 10   0   0   11  
Alyeska Mid (1700′) 20   0.3   0.1   21  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  16 E   9   30  
Seattle Ridge (2400′)  17   SE   17   35  
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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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