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Avalanche Advisory

Turnagain Area Avalanche Advisory
Sunday, February 17th 2019 7:00 am by Wendy Wagner
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche danger is rising to CONSIDERABLE due to new snow and wind over the region. Naturally occurring storm snow avalanches are possible and human triggered avalanches are likely. Fresh wind slabs, 1-2' thick, should be easily triggered on wind loaded slopes. Areas seeing over 10" of new snow should expect slab avalanches in wind sheltered zones. Additionally, expect natural cornice falls, sluffs in steep terrain and wet loose avalanches below 500'. Careful snowpack evaluation and conservative decision-making are essential if headed into avalanche terrain. 

SUMMIT LAKE / COOPER LANDING:  Central and Western Kenai mountains have seen 4-8" of new snow with more on the way. This area has a very poor snowpack with multiple weak layers. New snow avalanches are a concern, but triggering a slab 1-3' thick, breaking deeper in the snowpack is a much more dangerous problem. Watch for whumpfing, shooting cracks and recent avalanches.

SEWARD/ LOST LAKE:  Avalanche danger has risen in this region as well and storm snow avalanches are likely today. 

BYRON GLACIER TRAIL Hikers:  Natural avalanches may send debris to valley floors. Recognize and avoid being in the runout paths. Also, the popular snow cave is very dangerous and unstable. 


 Show the Complete North American Avalanche Danger Scale
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
3 Considerable Treeline / 1,000'-2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
3 Considerable Below Treeline / Below 1,000' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
Special Announcement
  • Avalanche danger is rising region-wide with new snow and wind. Hatcher Pass is calling for dangerous avalanche conditions - Please check their forecast HERE before heading this way.

  • GOOD LUCK to all the Iron Dog racers today! Friends of the CNFAIC along with forecaster Aleph Johnston-Bloom connected with riders Friday night at the 'Iron Dog Expo'.

                                          

Avalanche Problem 1

Storm Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

For anyone that was out yesterday, you may have noticed that the several inches of fluffy low-density snow greatly improved the surface conditions. Despite the good news, warmer temperatures have set in along with heavier and denser snowfall. The National Weather Service has continued their Winter Weather Advisory and is expecting an additional 7-10" of snow today. This has set the stage for touchy new snow avalanche issues. The old hard surface will provide a slick bed surface and yesterday's low-density snow will make it tough for the new heavier snow to stick right away. This type of storm, which begins cold and ends warm, is what we call in the avalanche world an 'upside-down' storm. 

If the forecast verifies and we really do see 7-10" of new snow we can expect:

  • Wind slab avalanches to be likely triggered on wind loaded slopes over 35 degrees
  • Storm slab avalanches in areas out of the wind where enough snow piles up to create a 'slab', typically around 10" of new snow or more
  • Sluffs on sleep slopes to be likely and should be occurring naturally as well
  • Cornices to grow and fall, likely triggering an avalanche on the slope below

All this said, the size of these avalanches is directly related to the amount of new snow. With somewhere between 10-18" of storm snow total by this afternoon, wind slabs should be in the 1-2' range and storm slabs in the 8-16" range. 

Storm Totals at mid-elevations as of 6am Sunday morning:
Turnagain Pass:    4-6"  
Girdwood Valley:   7-10" 
Summit Lake:       4-6"  
Bear Valley (Whittier Tunnel):  7-10"  
Moose Pass:  3-4"  
Seward (Exit Glacier):  4-6" 


Avalanche Problem 2

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

The load of the new snow today will again add stress to underlying weak layers. As we have been hammering home, roughly 1-3' below the snow surface sits a layer of buried surface hoar and in some areas facets in Turnagain Pass proper. Periphery zones such as Summit Lake and Johnson Pass harbor a weaker snowpack with a variety of weak layers. Although these layera have not been reactive lately, additional load may start to tip the balance. It is good to keep in mind that avalanches occurring today have the ability to step down and trigger a larger more dangerous slide. This is a more likely case for the Summit Lake and central Kenai mountains. 


Additional Concern

Glide Avalanches

Glide avalanches may be on the move again with the warm up seen over the past two days. Many cracks are present on heavily traveled slopes. The best way to manage this problem is to identify and avoid traveling directly below them.


Mountain Weather

Yesterday:  Overcast skies and light snowfall covered the region. Roughly 4-6" of low-density snow has fallen over the past 24-hours at most mid-elevations with the exception of Girdwood Valley that recorded up to 8". Ridgetop winds have been 15-25mph with gusts in the 40's from the east. Temperatures remained in the teens to 20F yesterday along ridgelines before warming up overnight to the mid 20'sF and the low 30'sF at sea level. 

Today:  Moderate to heavy snowfall adding 7 to 10" is expected over the course of the day with an additional 2-4" overnight. Warm air is streaming in and pushing the rain/snow line up to ~500'. Ridgetop winds are rising and forecast to average in the 40-50's mph from the east. Temperatures will sit in the mid 30'sF at sea level and in the mid 20's F above treeline. 

Tomorrow:  Another frontal system moves in on President's Day, which will continue our active weather pattern into the work week. Right now models are showing a cooling trend with this next system and snow to sea level. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 26  4-6  0.3  61 
Summit Lake (1400') 25  4-6  0.3  27 
Alyeska Mid (1700') 25  0.6  54 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 16  NE  13  47 
Seattle Ridge(2400') 22  SE   15 36 

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

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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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