Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sun, December 18th, 2016 - 7:00AM
Expires
Mon, December 19th, 2016 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

Strong winds along with several inches of new snow is expected to bump the avalanche danger to CONSIDERABLE. This will be  in the Alpine elevations that see over 5″ of snow accumulation. In these areas, fresh wind slabs up a foot thick may release naturally. Terrain that sees only 2-4″ of snow, this could include the Turnagain Pass area, will remain at a MODERATE avalanche danger. Any slope over 30 degrees with recent wind deposited snow is suspect for triggering a newly formed wind slab avalanche. Watch for wind slabs along ridgelines as well as lower on the slopes due to cross-loading.

Safer (and likely more enjoyable) areas to recreate today will be in treed zones where the wind has not affected the snow.  

***Portage Valley ice climbers and hikers: A MODERATE danger exists below 1.000′ where there is potential for avalanche debris, from a slide occurring above, to run through gullies. Avoiding gullies and runout zones is recommended.

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Sun, December 18th, 2016
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
  • 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

More blow than snow…? It looks like this may be the case for the storm that will be quickly moving through today. As of 6am this morning, Easterly ridgetop winds have jumped up and are averaging in the 30’s mph. Snowfall has just begun in Girdwood and a trace has fallen on Turnagain Pass. If you are thinking of heading out today, expect quite windy conditions and increasing avalanche hazard. 

We are expecting anywhere from 2-6+” of new snow today. In favored areas, with over ~5″ of new snow, we can expect the strong winds to form slabs quick enough that they release naturally. In areas with lower snow amounts, new wind slabs should be relatively shallow (6-10″). Slabs could also be a bit stubborn to trigger – keep this in mind as they could allow you to get out onto them before they release. Another thing, slabs may be thicker than expected if formed over Friday’s wind slabs, adding to the consequences. Remember, expect any slab you find to be sitting on weak faceted snow and poor bonding is likely.

What to watch out for:

  • Areas with current wind loading (winds should blow all day)
  • Slabs lower on slopes from cross-loading
  • Stiff snow over softer snow (punchy snow)
  • Cracks shooting from your feet
  • Whumfing sounds (collapsing of the snowpack into the faceted snow underneath)

 

Photo: Wind effect on the Sunburst Ridge yesterday. In the back you can see the cross-loaded Northerly slopes on Magnum. (Thanks to Sam Galoob for sending us this picture and report)

Avalanche Problem 2
  • Cornice
    Cornice
Cornice
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
More info at Avalanche.org

Watch for fresh cornice growth. Small chunks of fresh pieces of cornice are likely to fall today. 

Weather
Sun, December 18th, 2016

During the past 24 hours we have seen partly cloudy skies and no precipitation. Ridgetop winds were light yesterday and are ramping up this morning from an Easterly direction. Temperatures sit in the upper 20’s F at the lower elevations up to treeline and have cooled slightly on the ridgelines to the upper teens.  

Today, we will be on the North edge of a large area of low pressure heading East. This will usher in strong wind and some snowfall. Easterly ridgetop winds are on the rise currently and should peak with averages around 30-40mph and gusts 70-80mph. Snowfall numbers are unfortunately meager with only 3-5″ expected on Turnagain Pass, 1-2″ in Summit Lake and 8-10″ in the Portage Valley. The good news with the low staying so far South is temperatures should remain cool with a rain/snow line around sea level to 200′. Ridgetop temperatures will stay close the 20F with 1,000′ temps in the upper 20’s F.

An unsettled weather pattern will continue into the work week – it’s difficult to tell what kind of snow amounts we will see – stay tuned tomorrow morning!

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 26   trace – 1″ 0.1   23  
Summit Lake (1400′) 21   0   0   8  
Alyeska Mid (1700′) 28   0.5″ 0.06   15  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 19    NE 15   56  
Seattle Ridge (2400′) 22    SE   12   27  
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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
Closed.
South Fork Snow River Corridor
Closed
Closed.
Summit Lake
Closed
Closed.

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