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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   CNFAIC Staff  
Friday, November 26th 2010
Created: Nov 26th 6:30 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.
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.
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The Libby Group
The Bottom Line
Good morning backcountry travelers this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Friday, November 26th 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). This advisory will expire 24 hours from the posting date/time.

ANNOUNCEMENTS
Turnagain Pass and Johnson Pass North Trail Head motorized use areas are open for snowmobile use. Adequate snow is present to prevent resource damage. These areas consist of the lands on the west side of the Seward Highway between the Turnagain Arm and Sixmile Creek and the drainage Southwest of Bench Creek adjacent to the Johnson Pass North Trailhead south to Bench Lake. Center and Divide Creek Drainages are closed to snowmachine use.

All CNFAIC Staff areas of the Chugach NF are closed to motorized use until December 1st or adequate snow to prevent resource damage.

WEATHER ROUNDUP
-TEMPS: Are 8-10 degrees colder at most weather stations compared to yesterday morning and below freezing at all weather stations. Sometimes glide cracks react to temperature swings. A 10 degree change is fairly significant. Give the glide cracks extra space today.
-PRECIP: Turnagain Pass snotel was not working this morning, but CNFAIC Staff snotels in the surrounding region recorded 0.3-0.4 inches of water with 4-8 inches of new snow. There is 0.0 inches of water forecasted today; so, no additional load in the form of precip.
-WIND: I suspect that most ridgetop weather station anemometers are iced up and not functioning properly this morning; so its, tough the say exactly what the wind is doing right now. Seattle Ridge at 2400' appears to be working fine recording light winds averaging 0-9mph with a light max gust of 14mph in the past 24 hours. The National Weather Service is calling for moderate to extreme winds near Whittier today between 25-40mph. Watch out if these winds make it over to the mountains around Turnagain Pass.

Todays forecast for wind could increase the avalanche danger.

AVALANCHE DISCUSSION
The avalanche danger rating will remain at MODERATE due to the potential for small to medium sized human-triggered avalanches in the form of wind slabs along ridges and natural avalanches in the form of glide cracks that are widespread throughout the region.

The size of avalanches could increase today, if the wind increases and transports snow.

There is a 1/4 inch thick rain crust that extends up to the ridgetops to at least 3500' (most likely well above 4000'). It is widespread throughout the Turnagain Arm area. This crust has all the characteristic to become a very dangerous weak layer as soon as there is more snow on top of it. The snow on top of this crust seems to be bonding fairly well at lower to mid elevations where the snow fell at warmer temps. Above 2500', however, the snow on top of the crust IS NOT bonding well because of drier colder snow at these higher elevations. One of our observers found perfectly round ice pellets on top of the rain crust on Sunburst.

The 3 ingredients for dangerous avalanche conditions are: 1.)a slab, 2.)on top of a slippery bed surface, 3.)with a weak layer on top of the bed surface. We have 2 out of those 3. We are only missing a slab on top. Right now, the snow on steep slopes along the ridges just sluffs right off that rain crust.

Use extra caution along ridges where there are newly formed wind slabs or pockets of snow that look fat. These isolated pockets will not bond to the ice crust very well today. Pockets like these will be the most likely areas for human-triggered avalanches today.

The glide cracks and glide avalanches continue to be present, with new ones being observed region-wide on a daily basis. Be aware of your travel routes and try to avoid spending time below the cracks. The only way to reduce your risk from glide avalanches is to avoid traveling below the obvious cracks. We just had a fairly signifcant drop in temperatures. Sometimes glide cracks react to big temperature swings.


426-DSC_7351.jpg
This photo shows a good example of a glide crack and a glide avalanche on the South face of Cornbiscuit taken on 11-16-10. For scale take note that the crack is 4-6 feet deep. The glide crack on the left hand side of this photo has already avalanched; while, the glide crack on the right is still a hazard that could avalanche any day. Avoid traveling underneath glide cracks just like the one on the right hand side of this photo.

The Nation Weather Service weather forecast for:
WESTERN PRINCE WILLIAM SOUND-
INCLUDING...WHITTIER...SEWARD...GIRDWOOD...MOOSE PASS
500 AM AKST FRI NOV 26 2010
.TODAY...MOSTLY CLOUDY IN THE MORNING THEN BECOMING PARTLY SUNNY.
HIGHS IN THE UPPER 20S TO MID 30S. WEST WIND 25 TO 40 MPH NEAR
WHITTIER. NORTH WIND 15 TO 30 MPH NEAR SEWARD. NORTHWEST WIND TO 15
MPH ELSEWHERE.
.TONIGHT...MOSTLY CLOUDY. PATCHY FOG AFTER MIDNIGHT. LOWS 5 TO
15 ABOVE. NORTHWEST WIND 15 MPH.
.SATURDAY...MOSTLY CLOUDY WITH ISOLATED SNOW SHOWERS. HIGHS IN
THE UPPER 20S TO MID 30S...COOLEST INLAND. LIGHT WINDS.

TEMPERATURE / PRECIPITATION

SEWARD 36 16 33 / 0 0 20
GIRDWOOD 29 12 28 / 0 0 20

WEATHER STATION SUMMARY for Turnagain Pass:
3800-Sunburst Wx Station
Temp (4am): 14 (10 degrees colder than yesterday morning)
Winds: *Anemometer is probably iced up and not working properly*In last 24 hours winds have been light averaging 0-3mph with a light max gust of 5 mph

2400-Seattle Ridge Wx Station
Temp (5am): 17 (10 degrees colder than yesterday morning).
Winds: In last 24 hours have been light averaging 0-9mph with a light max gust of 14mph.

1800-Center Ridge Wx Station
Temp (8pm Thurs 11/25): Weather station not reporting this morning. CNFAIC Staff similar snotel sites in the region recored 0.3-0.4 inches of water and 4-8 inches of new snow.

The next advisory will be issued tomorrow Saturday morning 11/27/2010 at 7am. If you get out in the backcountry send us your observations using the button at the top of this page or call and leave a message at 907-754-2369. Thanks and have a great day.





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 25, 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

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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