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Turnagain Pass Avalanche Forecast RSS

Archives
ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Wed, December 25th, 2013 - 7:00AM
Expires
Thu, December 26th, 2013 - 7:00AM
Forecaster
Graham Predeger
The Bottom Line

For slabs that are persistent and snow not quite consistent, a MODERATE avalanche Danger exists for skiers and snowmachiners amiss.   Above tree line today a small wind slab may prove your biggest concern for Xmas-going fun seekers in Turn-again.   Below tree line, the danger is LOW where the snow on the ground is mostly stable and sound.

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Wed, December 25th, 2013
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

A generally poor structure to our snowpack is keeping the persistent slab our primary concern again today.  Avalanche activity appeared to peak on Sunday with two human triggered avalanches in the Turnagain area.  Cold temperatures and a lack of weather today will allow our snowpack to further adjust, however it doesn’t take long to dig down to the ground to recognize the problematic weak layers that lie beneath our slow-to-build slab.  Since the drizzle crust of December 7/8 (17 days ago) we have received 2.3 inches of water, which translates to about a 16-inch slab.  Snow pit tests yesterday were consistently failing at this interface of faceted snow directly above the crust.

Small spells of moisture thus far have allowed our snowpack to adapt a little at a time, not overloading weak layers to the point of widespread natural avalanching yet.  Add a skier or snowmachiner into the equation on steep, wind loaded terrain and producing an avalanche may be possible today.  Specifically in the higher elevations where the wind has produced a deeper, heavier slab that overlies this same basic poor structure.  

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

Monday morning we did have a short lived, natural wind slab avalanche cycle where strong winds proved enough to overload weak layers.  In higher elevation areas it’ll be possible to find pockets of dense wind slabs 1-2’ deep on the lee side of wind-raked ridges.  Pay particular attention to firm, hollow sounding snow on south, east and west aspects.  These slabs may sit mid-slope given the moderate to strong winds that blew through our region on Monday and Tuesday.

Weather
Wed, December 25th, 2013

Yesterday cloudy skies in the afternoon produced just a trace of new snow in eastern Turnagain Arm as a series of low-pressure systems skirted us to the south.   Winds shifted to a more easterly direction but still blew moderately yesterday.   Temperatures stayed cold at sea level due to a weak temperature inversion and gradually grew warmer with elevation topping out in the low-teens on Sunburst.

Don’t expect a Christmas miracle in the form of new snow today.   Rather we seem to have fallen under another persistent high-pressure ridge that appears to be with us at least until the weekend.   There is a decent temperature inversion in place this morning with temps ranging from 2 degrees in Portage to 20 degrees at the top of Sunburst.   Winds appear to again shift back to a northwest orientation today blowing in the 10-20mph range.  

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Riding Areas
Updated Fri, May 01st, 2020

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
Placer River
Closed
Skookum Drainage
Closed
Turnagain Pass
Closed
Closed as of May 1. Thanks for a fun, safe season!
Twentymile
Closed
Seward District
Carter Lake
Closed
Lost Lake Trail
Closed
Primrose Trail
Closed
Resurrection Pass Trail
Closed
Snug Harbor
Closed
South Fork Snow River Corridor
Closed
Summit Lake
Closed

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This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area. This advisory does not apply to highways, railroads or operating ski areas.