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Turnagain Area Avalanche Advisory
Sunday, February 28th 2010 6:38 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 Lisa Portune with the Chugach National Forest Avalanche Information Center on Sunday, February 28th 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).

WEATHER ROUNDUP
AnCNFAIC Staff 4-6 inches of new snow fell last night in Turnagain Pass, bringing our snowfall total for the last 3 days to around 12 inches of snow and 0.7 inches of water. Skies were mostly cloudy yesterday with a few sun breaks, ridgetop winds averaged 10-20mph out of the east and southeast with gusts to 35mph, and mountain temperatures ranged from the mid teens to upper 20s. As of 4am this morning, winds continue to average 10-20mph out of the east while temperatures have warmed up by about nine degrees to the low 20s. It is currently snowing in Girdwood with about 7 inches of new snow that fell last night. A large low pressure system and its associated front will move through our area today and tonight bringing an additional 9-14 inches of snow to the higher elevations. Look for rain to develop below 800 feet later today as temperatures continue to rise. Easterly ridgetop winds will average 10-25mph today while mountain temperatures will warm up to the mid 20s to low 30s.

AVALANCHE DISCUSSION
The avalanche hazard has increased since yesterday. Today the avalanche danger is rated CONSIDERABLE on all windloaded slopes steeper than 35 degrees. All CNFAIC Staff slopes have a MODERATE danger. We now have up to a foot of new snow on top of a slick crust and winds strong enough to transport this snow to leeward aspects. Wind slabs 1-2 feet thick near ridgetops will be sensitive to human triggers. As temperatures warm up and the snow continues to fall today, an increasingly top-heavy slab will form on top of the crust creating unstable conditions. Large sluffs are likely on steep non-windaffected slopes over 40 degrees and have the potential to run long distances. Human-triggered avalanches will be likely today on steep windloaded slopes with natural avalanches possible on any actively loading slopes. Rain on new snow will also cause almost instant natural avalanching, so be careful on lower elevation slopes later in the day.

Avalanche activity the last few days has been limited to sluffing on steep slopes and small windslabs near the ridgetops. I expect more action today as additional snow, wind, and warming temperatures create an upside-down slab on an extremely slick crust. This crust formed during the powerful Feb. 9-19 storm that pummeled our area with rain, high winds, and heavy dense snow at the higher elevations. The snow is like concrete underneath all this fluff and thus provides an excellent sliding surface for slab avalanches and sluffs today.

Jon and I toured up Lipps yesterday specifically looking for old buried surface hoar layers and the Jan. 7 rain crust. We easily found both at 2300 and 2800 feet on southwest aspects, but neither was reactive in our isolated column stability tests. The Jan. 7 crust was anywhere from 3 to 6 feet deep, and the buried surface hoar layer was consistently 6 inches above the crust. Both layers were smCNFAIC Staffed by extremely dense storm snow from the Feb. 9-19 storm. I think its going to take one heck of a storm to reactivate these layers at this point. At the least well see them again in the spring when the snowpack goes isCNFAIC Staffmal.

Numerous glide cracks formed this past week at the mid elevations, so keep an eye out for these gaping crevasse-like features that will swallow humans and sleds. As always, stay out from under them in case they decide to avalanche.

I 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 SUN FEB 28 2010

.TODAY...SNOW BECOMING RAIN AND SNOW IN THE AFTERNOON. SNOW
ACCUMULATION 2 TO 5 INCHES. HIGHS IN THE UPPER 20S TO MID 30S.
VARIABLE WIND 10 MPH.
.TONIGHT...SNOW. SNOW ACCUMULATION 3 TO 6 INCHES. LOWS IN THE MID
20S TO LOWER 30S. EAST WIND 10 TO 20 MPH.
.MONDAY...SNOW IN THE MORNING...THEN SNOW AND RAIN IN THE
AFTERNOON. SNOW ACCUMULATION 1 TO 3 INCHES OVER THE HIGHER
ELEVATIONS. HIGHS IN THE 30S. EAST WIND 10 TO 15 MPH EXCEPT EAST 25
TO 40 MPH THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.
.MONDAY NIGHT...SNOW AND RAIN. LOWS IN THE UPPER 20S TO MID 30S.
VARIABLE WIND 10 MPH EXCEPT EAST 10 TO 25 MPH THROUGH PORTAGE
VALLEY AND TURNAGAIN ARM.
.TUESDAY...RAIN. HIGHS IN THE MID 30S TO LOWER 40S. SOUTHEAST WIND 10
TO 20 MPH.

TEMPERATURE / PRECIPITATION

SEWARD 29 29 36 / 80 80 80
GIRDWOOD 29 29 37 / 80 80 80

WEATHER STATION SUMMARY for Turnagain Pass:
-3800 Sunburst Wx Station-
recorded light to moderate easterly winds yesterday averaging 10-20mph with gusts to 35mph. The current temp is 19F (8 degrees warmer than yesterday) with winds averaging 17mph out of the east.

-2600 Seattle Ridge Wx Station-
recorded light to moderate southeasterly winds yesterday averaging 10-20mph with gusts to 31mph. Winds are currently averaging 8mph out of the southeast this morning.

-1800 Center Ridge Wx Station-
recorded 4 inches of new snow and 0.2 inches of water in the last 24 hours. The current temp is 23F (9 degrees warmer than yesterday) with a total snowpack depth of 92 inches.
 Show the Complete North American Avalanche Danger Scale
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
3 Considerable Treeline / 1,000'-2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
3 Considerable Below Treeline / Below 1,000' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.

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

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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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