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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Saturday, February 20th 2016
Created: Feb 20th 6:22 am
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.
0 NO RATING Below Treeline / Below 1,000'
 Show the Complete North American Avalanche Danger Scale
The John Byrne Family
Special Announcement

Tonight is the night - Saturday, February 20th Hatcher Pass Avalanche Center is having their annual fundraiser at the Government Peak Chalet near Hatcher Pass. This event will feature a slide show by local climber and ski mountaineer, Kirsten Kremer, a Silent Auction, Live Music and FUN!  Click HERE for more info.


The Bottom Line

MODERATE avalanche danger exists today for fresh wind slab avalanches and cornice falls in the Alpine terrain. Wind slabs, up to 1 foot thick, will be possible to trigger on wind loaded slopes due to strong winds along ridgetops overnight and continuing today. At the mid-elevations, glide avalanches remain a concern where any one of the countless glide cracks can release at any time.

 If you are headed to the Summit Lake area, there are different snowpack concerns, see the Summit Lake Summary for more information. 

** There is a fast moving storm scheduled to arrive late this afternoon. Up to a foot, or more of snow is forecast from this afternoon through tomorrow morning. Avalanche conditions will increase rapidly in response to heavy snowfall. Stay tuned on tomorrow's advisory! 


Primary Concern

Today's primary concern will focus on the increase in winds from overnight and the strong winds forecast for today. There is just enough loose snow available for transport that fresh wind slabs are likely to form along ridgelines and other exposed slopes. Watching for the usual suspects such as cracking in the snow, stiff snow over softer snow, and smooth wind loaded surfaces will be key. Cornices are also something to keep in mind and continue giving a wide berth to.

Ok, now to the impending change in weather and increase in avalanche danger for tomorrow:  With a potent storm system at the doorstep, we are taking stock of not only how much snow will fall this weekend (up to a foot or more by tomorrow), but what types of surfaces it will fall on to. For those that have been enjoying the sunny days on Turnagain Pass last week, you will know that variable snow surfaces exist. These are: sun crusts on Southerly slopes, wind crusts on various aspects at all elevations and ridgelines and last, an abundance of soft loose faceting snow. On top of all these surfaces sits a layer of surface hoar that is anywhere from a few mm in size up to 2cm in places. What this all means is, any new snow that falls will fall on a weak layer of some type, limiting bonding between the new and old snow. In some areas, like South aspects, there will be a crust under the weak layer making bonding even more difficult. The good news is, we have strong winds today ahead of the snow which can blow over the surface hoar and generally make this set up less scary. But, this is not a sure bet and time will have to tell.

Surface conditions as seen yesterday along Seattle Ridge:

1-2cm surface hoar on top of Seattle Ridge                                          1-2cm sun crust with 3mm surface hoar on Southerly slopes
 


Additional Concern

We did not see, or have any reports, of any glide cracks that released yesterday. That said, it's the year to know where these cracks are and limit time under them as they can release with no warning.

Photo: Graham Predeger looks over at a large glide crack on the West side of Main Bowl (1st Bowl).


Mountain Weather

High clouds filtered over the region yesterday ahead of storm slated to move in this evening. During the past 24-hours winds have picked up slightly from the East along the ridgetops to the 10-20mph range and temperatures are holding steady, ~20F in the Alpine and ~30F at 1,000'. 

Today we should see mostly cloudy skies with winds increasing into the 25-35mph range from a generally East direction. These winds should be the main player in weather considering snowfall is not expected to begin in earnest till the afternoon. Once snowfall does begin, we could see up to 5" of snow by this evening (.5" of water equivalent) and another 5-10" (~1" water equivalent) by Sunday morning. The rain/snow line looks to be around sea level today then possibly raise as high as 1,000' tonight.

For Sunday, the main storm system looks to move out rather quickly but lingering instability showers and decreasing winds could add several inches of quality snow to the area. Temperatures look remain cold enough for snow to 1,000' for the duration of the storm. Stay tuned on tomorrow's advisory!

The Seattle Ridge weather station is back up with wind information - finally!! 

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 26   0 101 
Summit Lake (1400') 24  30 
Alyeska Mid (1700') 28   0 85 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 18  NE   13 39 
Seattle Ridge(2400') 20  SE 17  39 

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 16, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedThanks all for a safe and fun season on the Chugach NF! Stay tuned for the 2017/18 season. #playsafe #snowtosealevel
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail will be open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
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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