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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
Sat, January 18th, 2014 - 7:00AM
Expires
Sun, January 19th, 2014 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

A CONSIDERABLE  avalanche danger exists today both above and below treeline on all aspects. The brunt of yesterday’s warm, wet and windy storm has moved through but the snowpack is still adjusting to the shock. Though natural avalanche activity has slowed down with the end of precipitation and cooling temperatures overnight, human triggered avalanches are still likely. These avalanches have the potential to be large, break near the ground and take out entire slopes.

Very conservative travel is recommended again today. Simply put, this means avoiding all avalanche terrain (slopes 35 degrees or greater) including runout zones with steep slopes above you.  

For anyone thinking of heading up North, check out the Hatcher Pass Saturday am Advisory.

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Sat, January 18th, 2014
Alpine
Above 2,500'
Considerable (3)
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
Considerable (3)
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
  • Wet Loose
    Wet Loose
Wet Loose
Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
More info at Avalanche.org

Avalanche activity from yesterday:

Yesterday’s heavy rain below 2,000′ and wet snow above 2,000′ combined with very warm temperatures induced a widespread natural avalanche cycle. This extened to the Summit Lake area as well. We were able to get video footage of one natural slide in Portage Valley – video below. Additionally, the AK DOT Avalanche Program was able to trigger several large avalanches along the Seward Highway – one these can be seen in a video HERE.

The start zones for much of yesterday’s activity was in the dry snow above 3,000’. These slides turned wet as they descended due to entrainment of wet snow below treeline. You can see in the video below from Portage Valley how the powder cloud dissipates as the debris encounters the wet snow.

 

 

The slightly cooler temperatures along with breaks in cloud cover overnight will help limit any natural acitivity today. Much of the pack below treeline was draining water rapidly yesterday and today there may be a slight refreeze on the surface. The main areas of concern for wet avalanches will be near and just below treeline or in a gully at sea level elevations where debris can be funneled.

Avalanche Problem 2
  • 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

The shock of up to 3” of water weight in 24-hours yesterday did a number to the pack – as can be seen in the above videos and in our field day HERE. At the upper elevations this has added around 2′ of new snow along with rain on snow below treeline. The weak snow near the base of pack that is the culprit for many of our large avalanches is once again being overloaded. Though visibility was limited yesterday, it is likely that many of the debris piles seen occurred by an avalanche breaking near the ground and propagating across slopes at the mid to upper elevations. 

For today, the weather has abated but don’t count on the weak snow near the ground to have adjusted to the new load yet. There is much uncertainty going into today but the fact remains that during the past 24-hours we have had a significant avalanche cycle and there are slopes likely teetering on the edge just needing a human trigger.

Additional Concern
  • 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

At the upper elevations – above 3,000′ – temperatures were cold enough for around 2′ of snowfall during yesterday’s storm. Storm snow instabilities, mainly in the form of wind slabs are likely to be found and potentially triggered. With the warm temperatures these are likely to settle out within the 24-hour window – however, this is relegated to the storm snow and not the persistent slab issue mentioned above.

There is also the potentail for any storm snow avalanche to step down and trigger a larger slide breaking in the weak snow at the base of the pack.

Weather
Sat, January 18th, 2014

A fast moving and powerful storm moved through yesterday with rain below 2,000′ and heavy snow above. Ridgetop winds associated were from the East and averaged in the 50-60mph range with a max gust in the past 24-hours of 106. Temperatures at treeline were mainly in the upper 30’s and decreased to the low 30’s by the end of the precip.

Storm totals beginning Thursday night ending 6am this morning:
Turnagain Pass (1880′) –    2.2 € water, mostly rain (4 € wet snow)
Alyeska Mid (1700′) –  Roughly 3-3.5 € water, mostly rain (5 € wet snow)
Summit Lake (1400′) –   1.3 € rain

Overnight the skies have broken slightly as the main portion of the system is now to our North. There is a section of clouds and precipitation that is being wrapped around the low center which may add another 1-3 € of snow today. This has colder air entrained so snow levels should drop to around 400′. Ridetop wind today will be from the Southeast and in the 20mph range. Temperature at treeline will be around 30F and sea level mid 30’sF.

Sunday, another low pressure system heads our way that looks to be somewhat similar to yesterday’s storm. Stay tuned.

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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
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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.