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Turnagain Area Avalanche Advisory
Thursday, December 31st 2009 6:58 am by CNFAIC Staff
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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BROUGHT TO YOU BY
The Bottom Line
Good morning backcountry travelers this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Thursday December 31st at 7 am. This will serve as 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).

ANNOUNCEMENTS
All areas designated for snowmachines on the Chugach National Forest are open to snowmachines except Placer and 20 Mile. Please remember that Center and Divide Creeks near the Johnson Pass North Trailhead are always closed due to the current Forest Plan.

WEATHER ROUNDUP
Will recent weather effect avalanche conditions today?
Well, lets take a closer look at the precip, winds, and temps.

Hindcast (Last 24 hours)

3800 -Sunburst Wx Station-
wx station went down at 9 am yesterday; so I will use Fresno Ridge down at Summit for a general idea of Turnagain Pass weather

3400 Fresno Ridge Wx Station-
Temps ranged between 25-26 degrees increasing by 1 degree since yesterday morning with calm to light winds averaging 1-11 mph from variable directions with a max gust of 17

2400-Seattle Ridge Wx Station-
wx station went down yesterday 9 am yesterday, but we spent yesterday on Seattle Ridge working on this weather station and observed calm winds and mild temps

1800-Center Ridge Wx Station-
Precip: 0.0 inches of water
Total depth of 60 inches after 1" of settlement
Temperatures reached 31 degrees F yesterday and are currently the same as yesterday morning at 27 degrees F

Nowcast

Its hazy over Girdwood as of 5am but the moon is visible. The Middleton and the Kenai radars are mostly clear except for some light scattered precip. Most wx stations are not working this morning, but there does not appear to be any major weather happening right now.

Forecast

WESTERN PRINCE WILLIAM SOUND-
INCLUDING...WHITTIER...SEWARD...GIRDWOOD...MOOSE PASS
500 AM AKST THU DEC 31 2009
.TODAY...MOSTLY CLOUDY WITH ISOLATED SNOW SHOWERS IN THE
MORNING...THEN MOSTLY SUNNY IN THE AFTERNOON. PATCHY FOG. HIGHS IN
THE MID 20S TO LOWER 30S. LIGHT WINDS EXCEPT WEST 10 TO 15 MPH NEAR
WHITTIER.
.TONIGHT...CLEAR. LOWS 15 TO 25...COLDEST INLAND. LIGHT WINDS EXCEPT
NORTH AND WEST 10 TO 20 MPH NEAR SEWARD AND WHITTIER.
.NEW YEARS DAY...MOSTLY SUNNY. HIGHS 15 TO 25. LIGHT WINDS EXCEPT
NORTH AND WEST 15 TO 25 MPH NEAR SEWARD AND WHITTIER.

TEMPERATURE / PRECIPITATION

SEWARD 33 22 22 / 20 0 0
GIRDWOOD 25 18 20 / 20 0 0


Short Term Weather Models (NAM, WRF, QPF) for the Kenai Mountains near Turnagain Pass

Sea-level: The QPF is calling for 0.0-0.05 inches of water forecasted today, but the WRF is calling for 0.0 precip over Turnagain Pass.
3000: temps forecasted between 23 and 32 degrees F with winds 0-5mph
6000: temps forecasted between 14 and 23 degrees F with winds 5-10mph

AVALANCHE DISCUSSION
Today's weather should not contribute to the avalanche danger today at Turnagain Pass.

There are 4 main points of interest in the current snowpack

1.Stiffer snow and older wind slabs near ridgetops about 6 inches deep failed easily in compression tests on 12/28/2009 with scores as low as CTE2Q2@15cm. This stiffer snow did not appear reactive to ski, snowboard, or snowmachine tracks on big open planer slopes. We mention this type of shallow instability because it could be a problem in very rocky terrain above cliffs on extreme terrain.

2.A weak layer of buried surface hoar about 10-12 inches deep is generally confined to elevations below 2000'. Some people have reported seeing it a bit higher up to 2400', but most of it at lower elevations.

3.The facets on the ground are strangely starting to show slightly decreased stability since last week. These facets are generally rounding out, but have shown moderate failures with test scores as low as CTM13Q3@70cm. They show more activity where the snowpack is less than 3 feet deep, but were reactive as of Monday 12/28/09 in a 5 foot deep isolated column. Im not super concerned with these facets, but it does raise a few eyebrows. This data jives with a recent report where somebody observed some small slabs stepping down to the ground on steep terrain at about 1800. Maybe these facets will show themselves during the next big pineapple express if big storm snow avalanches step down to these facets.

4.A new layer of surface hoar has formed on the surface. It has been observed at lower and mid elevations. This will be a potential new weak layer to watch after it gets buried.

Due to a lack of significant weak layers and a mild weather forecast, the avalanche danger for Turnagain Pass will remain at LOW today. LOW is defined as: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Natural and human-triggered avalanches unlikely. Small avalanches in isolated areas or extreme terrain.

AnCNFAIC Staff concern today will be the glide cracks. A couple of large glide cracks have opened north of the snowmachine uptrack to Seattle ridge. Odds are there are numerous more of these crevasse like features which may be difficult to see. People and dogs have fallen into these cracks before, and they can be very difficult to get out of. Sometimes these glide cracks will avalanche, but this does not appear to be a concern today. Its always a good idea to treat glide cracks like cornices and avoid traveling underneath their path. Like cornices, glide cracks are very difficult to predict.

Always remember that safe backcountry travel requires training and experience. You control your own risk by choosing where, when, and how you travel.

Thanks for checking todays avalanche advisory. The next one will be posted NEXT YEAR on Friday January 1st. Happy New Year.

 Show the Complete North American Avalanche Danger Scale
1 Low Alpine / Above 2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
1 Low Treeline / 1,000'-2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

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: Jan 13, 2019 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Open
Placer River: Open
Skookum Drainage: Open
Turnagain Pass: Open
Twentymile: ClosedClosed. Forest Service is monitoring conditions.
Seward District
Carter Lake: Open
Lost Lake Trail: OpenPlease stay on trail to avoid resource damage through forested areas.
Primrose Trail: OpenPlease stay on trail to avoid resource damage through forested areas.
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: Open
South Fork Snow River Corridor: Open
Summit Lake: Open

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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