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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Monday, March 7th 2011
Created: Mar 7th 6:44 am
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.
 Show the Complete North American Avalanche Danger Scale
The Bottom Line
Good morning backcountry travelers. This is Wendy Wagner with the Chugach National Forest Avalanche Information Center on Monday, March 7th at 7am. 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).

BOTTOM LINE
The avalanche danger is generally LOW. There remain pockets of MODERATE danger for an avalanche to break into deeper weak layers creating a potentially unmanageable slide. These spotty trigger points are most likely associated with lingering hard wind slabs and can be found on steep wind loaded slopes with rollovers, rocky features and gullies. There are also pockets of MODERATE for sluffs initiated by direct sun on southern aspects.

AVALANCHE DISCUSSION
It was fairly quiet in the backcounty this weekend despite the warm temperatures, light wind and mostly sunny skies. It seems navigating the mixed bag of facets, crusts and wind slabs, all coming in a variety of thicknesses, have not been the highest on the priority list. Of note, and to add to the surface conditions, I did notice a thin sun crust over soft snow on a few south aspects where winds were calm yesterday.

A report came in from mid elevations in the Girdwood valley where enough warming initiated sluffing on south aspects with some sluffs propagating into small slabs. Calm winds and direct sun with the warming temperatures may increase this today. Watch for dampening of the surface and any rollerballs, especially under rocks or trees.

Today, the main concern is triggering a slab avalanche that fails in the weak sugary snow near the ground. These are most likely to be found in shallow wind loaded terrain where an older lingering wind slab can step down to the deeper weak faceted snow beneath. In this case a large avalanche may be triggered similar to many of the natural avalanches seen during the wind event over the last week of February. A look yesterday at a 3-4 foot deep snowpack in a NE starting zone ~3800 confirmed this concern showing extremely poor structure in shallow areas.

Smooth snow surfaces are clues to where wind slabs are present. These are most suspect for triggering on slopes that rollover or are unsupported (meaning no compressional support below, such as a slope above cliffs) along with shallow rocky areas and steep cross loaded gullies. As time goes on with no added precipitation these slabs are becoming more difficult to trigger. However, with the recent warm up in temperatures to around 30 degrees I did notice the old drifts becoming slightly more sensitive yesterday. This may again be the case today.

WEATHER ROUNDUP
Temperatures felt down right balmy yesterday anywhere out of the breeze. We hit the mid to upper 20s at 3500 and the upper 30s at 1000. Winds remained light with gusts in the 20s from an easterly direction. Overnight temperatures remained in the 20s at all stations above 300 with a very strong but shallow inversion below 300. Today expect sunny skies and temperatures in the upper 20s and 30s with light easterly winds. This persistent high pressure over the state looks like it is locked in place for now. The groomers are nice.

For kicks, some snowfall numbers:
We have had only 16-20 of new snow in the Turnagain Pass area in the past 4 weeks (since Feb. 4th, first day after the early February rain/snow event). No new snow is in the forecast, yet.

Center Ridge SNOTEL site:
November 123
December 29
January 63
February 31
To date, total snowfall is 246 which has settled to a snow depth of 81. SNOTELs do not track accumulated snowfall but we can compare current SWE (Snow Water Equivalent) and snow depth to the long term average. SWE is roughly 68% of average while snow depth roughly 83%.


ANNOUNCEMENTS An APU student is conducting a survey on backcountry skiing group dynamics. Click on the link to participate in research on avalanche safety. Click here to take survey

The Forest Service is installing winter use bridges across Granite creek in Turnagain Pass. Be aware of an ice road from the Lyon creek bridge south towards Johnson Pass on the West side of the highway. Heavy equipment will also be used in the area.

Jon will issue the next advisory tomorrow morning at 7am. If you get out in the backcountry give us a call at 754-2369 or send us your observations using the button at the top of this page. Thanks and have a great day.

The NWS weather forecast for:
WESTERN PRINCE WILLIAM SOUND-
INCLUDING...WHITTIER...SEWARD...GIRDWOOD...MOOSE PASS
500 AM AKST MON MAR 7 2011
.TODAY...MOSTLY CLOUDY WITH ISOLATED SNOW SHOWERS SOUTH OF MOOSE
PASS. ELSEWHERE...MOSTLY SUNNY. HIGHS IN THE MID 30S TO LOWER 40S.
VARIABLE WIND TO 10 MPH. NEAR SEWARD...NORTH WIND 10 TO 15 MPH.
.TONIGHT...PARTLY CLOUDY. LOWS 10 TO 25 ABOVE...COOLEST INLAND.
LIGHT WINDS EXCEPT NORTH 10 TO 15 MPH NEAR SEWARD.
.TUESDAY...MOSTLY SUNNY. HIGHS IN THE LOWER TO MID 30S. LIGHT
WINDS EXCEPT NORTH 10 TO 20 MPH NEAR SEWARD.
.TUESDAY NIGHT...CLEAR. LOWS 5 TO 25 ABOVE...COOLEST INLAND.
LIGHT WINDS EXCEPT NORTH 10 TO 20 MPH NEAR SEWARD.
.WEDNESDAY...SUNNY. HIGHS IN THE LOWER TO MID 30S. LIGHT WINDS
EXCEPT NORTH 10 TO 20 MPH NEAR SEWARD.

TEMPERATURE / PRECIPITATION

SEWARD 38 24 35 / 20 0 0
GIRDWOOD 35 20 33 / 0 0 0


WEATHER STATION SUMMARY for Turnagain Pass:
-3800 Sunburst Wx Station-
Temperature 22 degrees. NE wind around 10mph gusting into the 20's.
-2600 Seattle Ridge Wx Station-
Temperature 27 degrees. SE wind around 10mph gusting into the 20's.
-1800 Center Ridge Wx Station-
Temperature 29 degrees. No new snow.

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: Mar 15, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: OpenPlease park on road in and leave the turnaround (near outhouse) open for trailers to turn around.
Placer River: Open
Skookum Drainage: OpenSkookum drainage closes to motorized use on April 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: Open
Seward District
Carter Lake: Open
Lost Lake Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Primrose Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Resurrection Pass Trail: ClosedClosed for 2016/17 winter season. This is a non-motorized season. This alternates every other year and will open again during the 2017/18 winter.
Snug Harbor: Open
South Fork Snow River Corridor: Open
Summit Lake: Open

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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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