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Avalanche Advisory

Turnagain Area Avalanche Advisory
Friday, April 13th 2018 5:19 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 LOW this morning and will rise to MODERATE today for wet avalanches on sunlit slopes. If there are slopes that did not have a solid re-freeze last night, natural wet avalanches are possible and the danger could rise to CONSIDERABLE.  In the Alpine, triggering a slab avalanche around a foot thick remains possible where drier snow exists. Give cornices a wide berth.


 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.
2 Moderate Below Treeline / Below 1,000' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Special Announcement

Not only is the snow going through a springtime transition, the Avalanche Center is as well. It's that time to work on Annual Reports, end of season details and prepare for next season. Beginning next week, we will issue forecasts 4 days/wk on Sat, Sun, Tue, Thur. The final forecast will be on April 28th. The final Summit Summary of the year will be this Saturday. 


Avalanche Problem 1

Wet Loose

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

The snowpack is heating up and beginning to slide off the mountain sides. Not everywhere, but the usual suspects have seen large wet avalanches over the past couple days, with the majority of the activity two days ago on Wednesday. Pyramid's West face and the Southeast facing aspects of Seattle Ridge are these suspects and true to tradition, these slopes have seen the majority of the action. Although we have likely gone through the peak of acitivity for this first 'warm-up', any steep slope with a more shallow snowpack and baking in the sun is a concern for a naturally occurring large wet avalanche. 

For those headed out today, and this weekend, timing is everything. This morning, it's likely that the wet surface snow has undergone a fairly solid re-freeze and the avalanche danger is LOW. As the day heats up and the crusts melt and lose strength, the danger rises. This is when wet avalanches can begin to release, either naturally or by a person. Remember solar noon is around 2pm so the snowpack is the warmest, and most dangerous, from ~1pm till ~5pm. Once snow becomes wet and 'mushy' up to you boot top, or your track starts trenching in wet snow, it's time to head to a more supportable surface. Even a small wet avalanche can turn into something larger in bigger terrain. 

Photo below is on one example of the many large wet loose/wet slab avalanches on the Southeast face of Seattle Ridge occurring Wednesday.

 


Wider angle view of Seattle Ridge and the many large wet avalanches from Wednesday.

 

 
Large wet loose slides from Tuesday on the East face of Pyramid.

 

The West face of Pyramid continues to shed its snowcover as the days go by. Note the slabs on the lower looker's left of photo - these occurred sometime Wednesday evening/Thurs morning.


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Avalanche Problem 2

Storm Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Triggering a dry(ish) slab avalanche is still possible and occurred yesterday. A skier was caught and carried in a slab around a foot deep in the Johnson Pass zone. Skier was ok. This slope was at 4,900' on a West aspect. 

Upper elevation zones (above 3,500') received up to a foot of new snow on Tues/Wed this week while light rain fell down low. This 8-12" of snow is sitting on predominantly sun crust on E, S and West aspects. If you are in these higher elevation areas, such as near Whittier, Bench Peak, etc., watch for any new snow to become moist and possibly slide on the slick sun crust underneath. Hence, triggering a dry slab avalanche is still possible at the upper elevations. 


Mountain Weather

Yesterday, sunny skies with light Easterly winds were over the region. Temperatures climbed to the low 50'sF at 1,000' and to the upper 30'sF along the higher ridgelines at 4,000'. Overnight, a few clouds have moved in and temperatures have dropped to the 30'sF across the board - from ridgetops to sea level. 

For today, most sunny skies and another warm day are forecast. Temperatures should again reach 50F at 1,000' at Turnagain Pass, mid 50'sF at sea level and just under 40F along ridgelines. Ridgetop winds will remain light (5-10mph) from the East before slowly shifting Northerly by tonight. 

For the weekend, sunny and blue skies will be over the region. Ridgetop winds at this time are expected to be light and Northerly bringing in slightly cooler air. Temperatures should be on a textbook durnal trend with cooling overnight and warming during the day. Models are suggesting the possibility for light rain Monday into Tuesday associated with a low-pressure developing near the Aleutians. 

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 40   0 69 
Summit Lake (1400') 42  25 
Alyeska Mid (1700') 41  66 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  31 28 
Seattle Ridge(2400') 35  10  27 

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: Dec 01, 2018 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed
Placer River: ClosedClosed
Skookum Drainage: ClosedClosed
Turnagain Pass: ClosedClosed November 21 due to inadequate snow conditions. #hopeforsnow
Twentymile: ClosedClosed
Seward District
Carter Lake: ClosedClosed
Lost Lake Trail: ClosedClosed
Primrose Trail: ClosedClosed
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: ClosedClosed
South Fork Snow River Corridor: ClosedClosed
Summit Lake: ClosedClosed

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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
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