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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, February 14th, 2014 - 7:00AM
Expires
Sat, February 15th, 2014 - 7:00AM
Forecaster
Kevin Wright
The Bottom Line

A storm system is currently bringing snow to Eastern Turnagain Arm.  4 inches have accumulated by 6am, and another 5-9 inches are forecasted through the daylight hours today.  

Storm snow combined with wind and our old persistent slab problem may push us into  CONSIDERABLE  avalanche danger later today above treeline.  Below treeline is expected to stay  LOW to MODERATE  without wind loading.  

We can piece out the various avalanche problems today, but the overall concern is related to the snow since February 7th.  This snow is still soft, but rests on a very hard crust layer and may not be bonded well to the crust.  

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Fri, February 14th, 2014
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
  • 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

We continue to document loose and very weak facets between the January melt/freeze crust and the February 7th storm snow.  This layer was responsible for a number of small human triggered avalanches in the last week.  It continues to be the most likely culprit for significant avalanche activity today, especially when combined with new snow and wind.  Check out this observation for photos and snowpit data regarding the facet layer.  

Avalanches witnessed on this layer have thus far maintained a consistent pattern with relatively small size (12-20″ deep), and lower volume.  Keep in mind that bigger and steeper terrain will produce larger and more dangerous avalanches.  With more snow and wind the depth of this slab layer will be reaching 24-30″ in wind loaded areas.  

The 2 properties necessary to create this type of avalanche that are not always found –

1.  A cohesive slab – some wind loading and stiffening is necessary to create connectivity of the surface snow, otherwise it’s just loose powder with sluff potential.

2.  A faceted interface between the new snow (Feb 7th storm) and the underlying crust (January melt/freeze).  In places where the facets are present, this is a significant weak layer consisting of loose sugary grains with poor bonding.  

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

Yesterday afternoon we witnessed a very small natural avalanche occur during a short spell of wind.  Our light dry snow on the ground is easily transported by wind and wind slab can build quickly with only moderate wind velocities.  Additional storm snow by itself is probably not enough to be a significant avalanche problem, but combined with wind it will produce pockets of unstable snow.  

Wind slab is expected to be isolated to higher elevations above treeline, and may not form if the wind stays light today.  

Weather
Fri, February 14th, 2014

Just a couple inches of snow had fallen yesterday before we got a clear break and periodic wind activity.  Wind was reaching gusts to 52 mph and blowing snow around at ridgetop levels.  

The large low pressure system over Kodiak is sending our region waves of cold precipitation today.  As of this morning we have another 3-5 inches of snow on the ground and it is forecasted to continue through the end of Friday.  Wind has backed off a little.  Temperatures remain cold but are increasing slightly.  Currently Center Ridge snotel is reading 11.5 degrees.

Unsettled storm patterns will continue through the weekend, originating from the low pressure system in the northwest gulf.  We can expect more of the same weather for a few more days.

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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

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Turnagain Pass
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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.