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Avalanche Advisory

Turnagain Area Avalanche Advisory
Thursday, December 20th 2018 7:00 am by Heather Thamm
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

Travel is not recommended today in avalanche terrain due to HIGH avalanche danger at all elevations. Large natural avalanches 3-5+’ thick are very likely in the upper elevations due to heavy snow at all elevations. A Special Avalanche Warning has been issued for the mountains surrounding Turnagain Pass, Portage Valley and Girdwood Valley. This also includes Johnson Pass and Lynx Creek drainage.

PORTAGE: In Portage Valley where 2-4’ of snow has fallen in the upper elevations avalanches could run their full length to valley bottoms. Avoid being near any avalanche paths.

SUMMIT LAKE: In Summit Lake a very weak and shallow snowpack exists and human triggered avalanche 2+’ thick are likely in avalanche terrain. 

 


 Show the Complete North American Avalanche Danger Scale
4 High Alpine / Above 2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4 High Treeline / 1,000'-2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4 High Below Treeline / Below 1,000' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
Special Announcement

Many riding areas on the Chugach National Forest have opened near Seward. Be aware of increased avalanche danger today. Very little info exists about the snowpack in these zones. Turnagain Pass is being assessed. An up-to-date riding status is available at the bottom of this page.

Due to an unexpected amount of snow in the last 24 hours and up to a foot more today, please be aware that parking areas will not be plowed until roads are cleared. Please yield to DOT plow drivers and let them focus on the road. 

If you're thinking of heading to Hatcher Pass be aware of dangerous avalanche conditions in this zone. Check out the Hatcher Pass Avalanche Center mid-week summary HERE. 

 


Avalanche Problem 1

Storm Slabs

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Today we recommend avoiding the backcountry due to HIGH avalanche danger. Heavy snow has been falling over the last 24 hours and is expected to continue through early afternoon. The estimated snowfall for Turnagain Pass is 4-5’ and more snow is expected through early afternoon. Snowfall rates have been in the 6”/hour (0.2 - 0.3” SWE/hr) overnight at the Turnagain Pass SNOTEL and 1-2”/hour in Portage and Girdwood. This is an unprecedented amount of snow in a very short period of time and natural avalanches could run far distances and very fast. Avoid all avalanche terrain including slopes steeper than 30 degrees and stay far away from any runout zones. In Portage Valley where channeled terrain runs to sea level avoid any trails with steep slopes above, like Byron Glacier trail. As an alternative to the backcountry, consider going to Alyeska!!! Santa’s ski for free today.

 24-hour Precip:

  • Turnagain Pass SNOTEL: estimated 4-5 feet (3.4” SWE)
  • Portage Valley: 22” (1.03” SWE)
  • Girdwood – Alyeska Midway: 20” (1.04” SWE)
  • Summit Lake: 10” (0.4” SWE)

The snow stake at Turnagain Pass DOT lot shows ~ 3-4 feet of new snow in the last 24 hours. 

 

Crowns from natural storm snow avalanches were seen yesterday in the Girdwood Valley at around 2500'. In this zone there was 13" new snow mid-afternoon.  


Avalanche Problem 2

Persistent Slabs

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In thinner snowpack zones such as Summit Lake we are tracking buried layers of facets, crusts and buried surface hoar that sit 2-3' under the snow surface. 10” of snow has fallen over night in Summit Lake and 6-12” is possible today. This new snow and moderate ridgetop winds may be adding more stress to an already weak snowpack. Triggering a slab near the ground is likely in avalanche terrain. The Lynx Creek and Johnson Pass zone have little to no snowpack data and often have a similar snowpack to Summit Lake. These zones are now open to snowmachining and this area likely received 2-3’ of snow in the last 24 hours. Today is not the day to push into Johnson and Lynx. HIGH avalanche danger is expected in this zone similar to Turnagain Pass.


Mountain Weather

Yesterday: Heavy snowfall started around 8am and has continued through this morning. An estimated 4-5’ has fallen at Turnagain Pass (3.4” SWE.) The Portage Rail Road Weather station is reporting 22” at sea level (1.03” SWE) and Alyeska midway is similar. Temperatures have remained in the mid to low 20F’s in the lower elevations and in the teens F at ridgetops. Ridgetop winds have been from the East 15- 30mph with some higher gust.  

Today: A band of moisture and low pressure continue to pump snow through the Eastern Turnagain Arm region (North of Moose Pass to Girdwood.) The weather service has issued a winter storm warning with an additional 6-16" is possible through early afternoon. Temperatures are expected to remain in the low 20F’s to low teens (F). Ridgetop winds will be light to moderate.

Tomorrow: An active weather pattern will continue tomorrow into the weekend with more snow showers in the forecast. Temperatures are expected to be in the 20F’s with light to moderate winds. 

*Seattle Ridge weather station is rimed over and not recording any data. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 20  46" 3.4 85
Summit Lake (1400') 16  10"  0.4  23 
Alyeska Mid (1700') 20  20"   1.04 40 

 

RIDGETOP 24-hour data (6am - 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 13  ENE  14  37 
Seattle Ridge(2400')  *N/A  *N/A   *N/A   *N/A 

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).

Winter snowmachine use open/closed status and riding conditions updates

Riding status is not associated with avalanche danger. An area will be open to motorized use in accordance to the Forest Management Plan when snow coverage is adequate to protect underlying vegetation. Backcountry hazards including avalanche hazard are always present regardless of the open status of motorized use areas.

(Updated: May 06, 2019 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed as of 4.3.19
Placer River: ClosedClosed as of 3.20.19 due to lack of snow.
Skookum Drainage: ClosedPlacer access closed as of 3.20.19 due to lack of snow.
Turnagain Pass: ClosedClosed as of 5/6. Thanks for a great season all, see you next winter!
Twentymile: ClosedClosed as of 3.20.19 due to lack of snow.
Seward District
Carter Lake: Closed
Lost Lake Trail: ClosedClosed as of 3.22.19 due to lack of snow
Primrose Trail: ClosedClosed as of 4.3.19 due to lack of snow
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: ClosedClose as of 5.1.2019
South Fork Snow River Corridor: ClosedClosed as of 3.20.19 due to lack of snow.
Summit Lake: Closed

Subscribe to the Turnagain Area Avalanche Advisory:

The information in this advisory is from the U.S. Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur. This advisory provided by the Chugach National Forest, in partnership with Friends of the Chugach National Forest Avalanche Information Center.


USFS SNOW AND AVALANCHE HOTLINE (907) 754-2369
If you have comments or questions regarding CNFAIC operations or winter recreation management, please email staff@chugachavalanche.org
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