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Avalanche Advisory

Turnagain Area Avalanche Advisory
Wednesday, December 12th 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

The avalanche danger is MODERATE in the Alpine and at Treeline where triggering a slab 1-3’ deep is possible. Keep an eye out for glide cracks and avoid traveling underneath this unpredictable avalanche hazard. Assess the snowpack as you travel, identify areas of concern and evaluate terrain consequences.

UPDATE: An unexpected sleeper storm is upon us!! We've seen 6-12" in the Girdwood Valley and 3" in Turnagain Pass between 6am and 10am. This is a very low density snow storm with little volume and little wind. Expect 'sluffs' in steep terrain and pay attention to new snow accumulation. In areas recieving a foot or more of snow the avalanche danger could increase to CONSIDERABLE.


 Show the Complete North American Avalanche Danger Scale
2 Moderate Alpine / Above 2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
2 Moderate Treeline / 1,000'-2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Special Announcement

If you are heading to Hatcher Pass make sure to check out the latest observations HERE for details on several human triggered avalanches that occurred Sunday. Be aware alaskasnow.org is undergoing a systemwide website update and Hatcher Pass Avalanche Center webpage may be temporarily unavailable today.   

Looking for avalanche courses or evening presentations? Check out our calendar page! There are two CNFAIC evening discussions coming up - these are FREE and a great way to get your head back in the avalanche game. Tomorrow - 'Tales from the Pit' at Blue & Gold Boardshop in Anchorage!


Avalanche Problem 1

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
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Size

Incremental loading over the last three days and more observations have nudged the mid-elevation band to MODERATE danger for triggering a slab 1-3’ thick releasing on weak snow. Yesterday on Magnum Mountain widespread ‘whumpfing’ caused a group to turn around at 2300’. A reactive layer of facets between two crusts showed easy propagation and they had low confidence in continuing into steeper terrain. This is a good reminder that it is still early season and limited snowpack observations exist across the forecast zone. Areas with a thinner snowpack are more suspect for weaker and unstable snow including the Southern-end of Turnagain Pass, Summit Lake and Girdwood Valley.

In the Alpine on the Northern end of Turnagain Pass stability tests have been showing a strengthening snowpack. However keep in mind North and East aspects have a tendency to be thinner and there is a zone in the mid-elevations where the snowpack quickly transitions to shallower depths. 

As always be on the lookout for red flag warnings like whumpfing’, shooting cracks, new avalanche activity and any changes in weather. Today a 1-3" inches of snow is expected and there is currently 4-8” of loose snow available for transport. Should ridgetop winds increase above the forecasted 5-15mph, keep an eye out for active wind loading. Any sign of increased winds could form wind slabs or add stress to a persistent slab.

One of three pits between 2000' and 2300' on Magnum's NW shoulder that showed poor structure and propagation potential in stability tests


Avalanche Problem 2

Glide Avalanches

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
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Size

Yesterday several glide cracks were noted on the Southwest face of Sunburst below the weather station. A glide crack is the snowpack being pulled by gravity downhill along the ground. They can release at any moment without warning and are usually not associated with human triggers. The best way to manage this hazard is to avoid being on or beneath any slopes with cracks opening up. 

These are the first glide cracks of the season and we hope the last.  If you see any new glide cracks in other areas, snap a photo, and send us an observation HERE. This helps us provide better information in our forecasts.  

 


Mountain Weather

Yesterday: Snow showers ended yesterday morning and skies were partly cloudy. Temperatures fell throughout the day from the upper-20Fs into the low-20F’s. Overnight ridgetop temps have fallen into the teens F. Winds were light and variable.

Today: Light snow flurries started early this morning. A few inches of snow (1-3") is possible today across our region at all elevations. Temperatures will remain in the low 20F’s at 1000’ and low-teens F near ridgetops. Light Westerly winds 5-10 mph are expected to increase 10-15mph later this evening.  

Tomorrow: Temperature will remain in the low 20F’s to low teens. Partly sunny skies are in the forecast for tomorrow and light winds. Friday into Saturday looks like our next best chance for snow showers.

*Seattle Ridge weather station anemometer is rimed and not recording wind data.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 25   29
Summit Lake (1400') 24  0.1 
Alyeska Mid (1700') 25 2 0.16 13

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 17  variable 
Seattle Ridge(2400') 23  *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

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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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