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Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Fri, January 4th, 2013 - 7:00AM
Expires
Sat, January 5th, 2013 - 7:00AM
Forecaster
John Fitzgerald
The Bottom Line

The avalanche hazard remains at HIGH today above treeline, where over a foot of new snow and winds have added stress to the snowpack.   Above treeline today human triggered avalanches are very likely.   Below treeline the hazard is CONSIDERABLE, where human triggered avalanches are likely.

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Fri, January 4th, 2013
Alpine
Above 2,500'
High (4)
Avalanche risk
Treeline
1,000'-2,500'
Considerable (3)
Avalanche risk
Below Treeline
Below 1,000'
Considerable (3)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
High (4)
Treeline
1,000'-2,500'
Avalanche risk
Considerable (3)
Below Treeline
Below 1,000'
Avalanche risk
Considerable (3)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Deep Persistent Slabs
    Deep Persistent Slabs
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
More info at Avalanche.org

The skier triggered avalanche that occurred on Jan 2 is a good reminder that many slopes are capable of producing large, deep and destructive avalanches.  This avalanche showed us a snowpack that is remarkably dangerous, as smaller avalanches occured on adjacent slopes as a direct result of this slide.  This event should be a wake up call to us all.  While the outcome was good (no one was injured, buried or killed), it easily could have turned out much differently.  Check our observations page for a variety of reports about this avalanche.  The potential to trigger deep slabs will remain today, as over a foot of new snow combined with wind has added stress to the snowpack.  While the precip has backed off in intensity since yesterday afternoon, the snowpack needs time to adjust to its newest load.  While time will help to diminish the likelihood of triggering these deep slabs, it will not erase it.  The consequences of triggering a deep slab avalanche are severe.  Conservative terrain choices combined with safe travel practices will be essential in avoiding this problem today.

Avalanche Problem 2
  • 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

While 15″ of snow is a significant load on an already stressed snowpack, 1.5″ of water weight is even more significant.  If we were to get the same amount of snow with, say, a quarter inch of water, the stress placed on the underlying layers would be much less significant.  Any time I see an inch of water or more of accumulation in a 24 hour period I pay attention.  Expect to find areas with greater accumulation, particularly above treeline and in wind loaded starting zones today.  While the sensitivity of these slabs will be on the decline, do not rule out the possibility of layers within this new snow to release and produce avalanches.  The greater problem arises when this new snow slides and brings out weaknesses deeper down into the base of the snowpack.

Weather
Fri, January 4th, 2013

The past 10 days has added a lot of weight and stress to our snowpack, as evidenced here by our friends at Alyeska resort.   While there have been brief moments of reprieve, the faucet turned back on yesterday with Turnagain Pass picking up 15″ of new snow with 1.5″ of water.   At the Sunburst station, winds have averaged 32 mph out of the E with gusts to 80.   Temps at 3800′ have been in the 20s F, with freezing levels hovering around 500′.
Today expect lingering snow showers with up to 4″ of new snow possible.   Winds will be out of the E and SE at 20-30 mph and temps at 1000′ will be around 30 F.
The extended outlook calls for a continuation of unsettled weather, with the next significant chance for snow on Saturday afternoon.

______________________________________________

Kevin will issue the next advisory on Saturday, January 5th.
 

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Riding Areas
Updated Mon, October 26th, 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
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.