Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sat, February 25th, 2017 - 7:00AM
Expires
Sun, February 26th, 2017 - 7:00AM
Forecaster
Aleph Johnston-Bloom
The Bottom Line

The avalanche danger is  MODERATE  above 2,000′ in the Alpine where triggering a 2-3′ slab avalanche on slopes steeper than  35 degrees is still a possibility on all aspects. In addition, there are a handful of other avalanche concerns including shallow wind slabs, cornice falls, sluffs and glide avalanches.  

Below 2,000′ there is a  LOW  danger where triggering an avalanche is unlikely due to a snowpack consisting of hard crusts.

In Summit Lake, Girdwood, and on the southern end of Turnagain near Johnson Pass triggering a deeper more dangerous avalanche near the ground is still possible, but will be hard to trigger.

Check out the Saturday Summit Summary HERE.

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Sat, February 25th, 2017
Alpine
Above 2,500'
Moderate (2)
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
Moderate (2)
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
  • 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

Above 2000′ where the rain crusts disappear the layer of surface hoar that was buried by the mid February storms is lingering as a concern in the advisory area. Relatively calm weather has been over the region for a few days now. This has allowed for folks to push further into the mountains with no reports of avalanche activity since last Saturday. However, this weekend it is important remember that poor snowpack structure still exists with this thin layer of buried surface hoar sitting 2-3′ below the surface and the slab is large enough that the consequences could be high if you find the wrong spot. Triggering an avalanche breaking on this layer is becoming tougher by the day as the snowpack slowly stabilizes and adjusts but the possibility shouldn’t be forgotten. 

The most likely place to find one of these larger slides is on steep slopes with thin areas and rock bands. Trigger points are often these thin areas, near rocks and zones that may have been scoured slightly by winds. Also, these slabs can break above you, and release after several tracks are on a slope. Be aware that snow pits and stability tests may not be representative of the actual slope you are trying to assess. A helpful way to think about this problem is to consider the consequences of a slope if it slides and identify and avoid terrain traps (gullies, cliffs, or trees below).

Deep Persistent Slab: Various layers of weak faceted snow sits at the bottom of the pack in certain areas. In the Summit Lake zone and some areas in Girdwood Valley and towards the southern end of Turnagain near Johnson Pass depth hoar has been found. Similar to the problem above, these layers will be very tough to trigger, but a possibility remains in places with this structure. 

Snow pit profile from Sunburst on Tuesday. Note the structure: buried surface hoar sandwiched below a stiff slab and stiff potential bed surface.

 

Snow pit on Thursday showed similar stucture across the road on Seattle Ridge.  In both locations tests showed that the layer was harder to trigger but still a possibility.

 

Avalanche Problem 2
  • Wind Slabs
    Wind Slabs
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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

Wind slabs: Loose surface snow combined with W-NW ridgetop winds in the 10-20 mph range gusting into the 30s overnight may have formed shallow wind slabs on leeward features. The snow may feel “upside down” with slightly stiffer snow over softer snow. Look for areas of pillowed or drifted snow and identify steep features like convexities or gullies where the snow may be more loaded.  Blowing snow and shooting cracks will be obvious clues to look for today. 

Loose snow avalanches: The top 6” of surface snow is loose and sluffs may be easy to initiate and fast moving on steep terrain features protected from the winds. 

Cornices: Remember these unpredictable hazards can break farther back onto a ridge than expected and have the potential to trigger an avalanche on the slope below. Give cornices extra space and avoid being under them. 

Glide avalanches: There is a new glide crack above the flats along Seattle Ridge, just looker’s left of the up-track and Repeat Offender slide path. Avoid hanging out under this crack and any others you may see – these release without warning and are very destructive.

Sunshine: Today skies may be be partly sunny and solar warming may trigger loose snow avalanches in steep Southerly aspects. 

Wind effect just South of Pyramid Peak on Thursday.

 

Weather
Sat, February 25th, 2017

Yesterday was mostly cloudy with a few light snow showers during the day favoring Girdwood. Temperatures were in the mid to high 20Fs with a few low elevation stations seeing above freezing for a few hours. Winds were light during the day and then picked up overnight from the W-NW 10-20 mph gusting into the 30s.

There was clearing overnight but clouds are forecasted to move back in today. Temperatures will be similar to yesterday and winds will be light and continue to be from the NW. There is a slight chance of snow overnight tonight.  

Sunday looks to be similar with an increasing chance of snow showers into Monday. Cold, clear weather is forecasted later next week.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 27   0   0 67  
Summit Lake (1400′) 24 0   0   32
Alyeska Mid (1700′) 24    1 .05 62

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 24 WNW 10   32  
Seattle Ridge (2400′)  26  NW 15   39  
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Riding Areas
Updated Wed, December 11th, 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
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South Fork Snow River Corridor
Closed
Closed.
Summit Lake
Closed
Closed.

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