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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
Tue, December 9th, 2014 - 7:00AM
Expires
Wed, December 10th, 2014 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

A  CONSIDERABLE  avalanche danger exists this morning on all aspects above 1500ft. Below 1500ft a lack of snow cover results in No Rating. Over the past 48-hours, heavy rainfall at the mid-elevations and below has created widespread natural wet avalanche activity. With a decrease in precipitation expected today, natural avalanche activity is expected to decline. However, human triggered wet avalanches, up to a foot deep, will remain likely on slopes steeper than 35 degrees. Areas of most concern are all aspects in the elevation band from 1500ft to 3000ft. At the high elevations above 3000ft, storm snow instabilities exist in the form of wind slabs, cornices and loose snow sluffs.

For today, avoiding slopes steeper than 35 degrees harboring  saturated and wet snow is recommended. In the upper elevations with dry or moist snow, cautious route finding and skilled snowpack evaluation is essential.

——————————————————————–

The next advisory will be Thursday Dec11th at 7am.

Avalanche Outlook for Wednesday: The avalanche danger is expected to decrease Wednesday due to a decrease in precipitation and a possible break in cloud cover. Temperatures should remain very warm however and extra caution will continue to be warranted for wet avalanches below 3000ft and wind slab avalanches above 3000ft.

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Tue, December 9th, 2014
Alpine
Above 2,500'
Considerable (3)
Avalanche risk
Treeline
1,000'-2,500'
Considerable (3)
Avalanche risk
Below Treeline
Below 1,000'
No Rating (0)
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
No Rating (0)
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

Yesterday marked the second, and most intense, period of rain on snow. Many wet loose avalanches were observed on all aspects along with two wet slab avalanches between 1500ft to 3000ft (photos below). Today precipitation is expected to decrease with potentially .3-.5″ of rain falling below 2500ft.

Wet avalanches are common during extended periods of rain and warm temperatures. They typically start on steep terrain with rollerballs initiating under cornices, trees, rocks or underfoot that subsequently entrain more and more snow as they gain momentum and move downslope. If caught in a wet avalanche it is very difficult to escape as the heavy wet snow can quickly knock you off your feet, twist a knee or break a leg. Debris has the potential to run further than expected due to a melt/freeze crust 8-18″ below the surface (mid-pack) providing a uniform sliding surface.

Photo below is a wet slab avalanche on the West face of Lipps Ridge (2800ft).

 

Wet loose avalanches off of Tincan’s Southwest facing CFR ridge (2500ft)

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

Despite the grim facts concerning the wet snow stated above, at the high elevations it is snowing. Above 3,500′ new snow amounts during the past 48-hours are estimated between 2 and 3+ feet in the Turnagain Pass zone – up to twice that in other areas such as Portage and the Girdwood Valley. We have little information on how this new snow is adjusting, however what we do know is this is a significant load in a short period of time that warrants respect.

Storm snow instabilities will be in form of wind slab, cornices and loose snow sluffs. With ridgetop winds and precipitation decreasing overnight, these instabilities should gain strength rather quickly. This is due to the warm temperatures of the new snow along with no known preexisting weak layers in the snowpack at these upper most elevations. 

 

Additional Concern
  • Glide Avalanches
    Glide Avalanches
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
More info at Avalanche.org

Although we did not see any glide avalanche activity yesterday, the poor visibility and known existence of glide cracks between 1,500 and 3,500′, is enough evidence that these types of avalanches remain a concern. As with the travel advice for wet avalanches above, today is a day to avoid slopes steeper than 35 degrees and to steer clear of runout zones.

Weather
Tue, December 9th, 2014

Yesterday’s weather was warm, wet and windy. During the past 48-hours Turnagain Pass has received 2.5 inches of water with greater amounts in the Girdwood and Portage Valleys. The rain/snow line hovered ~2000 feet yesterday and possibly up to 2500 feet in areas. Ridgetop temperatures have been ~30F and winds were predominantly from the East, averaging 30-40mph with gusts in the 60’s.  

Overnight, temperatures have increased slightly and the rain/snow line looks to be just above 2000 feet with precipitation diminishing. Winds have also decreased and are remaining steady in the teens to 20’s mph along ridgetops from the East.  Today, Tuesday, we are expecting .3-.5″ of rain below 2000-2500′ with 2-4″ of wet snow above. Ridgetop Easterly winds should remain in the 10-20mph range with temperatures near 30F.

The low-pressure system that moved through yesterday is headed inland today bringing a slight break in precipitation. However, warm temperatures are expected to continue over the next few days with periods of light rain and freezing rain. This should continue through Thursday, followed by another low-pressure system that could bring more precipitation closer to the weekend for Southcentral Alaska.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 36   0   1.4   19  
Summit Lake (1400′) 35   0   0.2   4  
Alyeska Mid (1700′) 37   0   1.3   12  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 29   E   25   61  
Seattle Ridge (2400′) 31   E   18 47  
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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.