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Turnagain Area Avalanche Advisory
Wednesday, January 20th 2010 7:04 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 Wednesday January 20th 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).


WEATHER ROUNDUP
Hindcast (Last 24 hours)

3800 -Sunburst Wx Station-
Current temp is 23 (2 degrees warmer than yesterday) Winds have been light to moderate averaging 7-23 mph out of the east with a strong max gust of 35 mph

2400-Seattle Ridge Wx Station-
Winds have been light averaging 4-15 mph out of the ESE with a moderate max gust of 22mph

1800-Center Ridge Wx Station-
Current temp is 27 (6 degrees warmer than yesterday) Zero to 0.1 inches of water and 1-2 inches of new snow has fallen.

Nowcast

Temps are warmer at all wx stations this morning by 1-6 degrees compared to yesterday. The precip amounts are consistent at all snotel sites this morning with probably 1-2 inches of new snow. Winds are currently light at all ridgetop wx stations this morning. Both the Middleton and Kenai radars shows very scattered light precip moving W toward the southern Kenai Mountains.

Forecast

WESTERN PRINCE WILLIAM SOUND-
INCLUDING...WHITTIER...SEWARD...GIRDWOOD...MOOSE PASS
550 AM AKST WED JAN 20 2010

.TODAY...CLOUDY WITH SCATTERED RAIN AND SNOW SHOWERS...MAINLY ALONG
THE COAST. DECREASING CLOUDS IN THE AFTERNOON. AREAS OF FOG REDUCING
VISIBILITY TO ONE HALF MILE OR LESS IN THE MORNING. HIGHS IN THE MID
20S TO MID 30S. LIGHT WINDS EXCEPT NORTH 10 MPH NEAR SEWARD.
.TONIGHT...PARTLY CLOUDY. LOWS 15 TO 25. NORTH TO WEST WIND 10 TO 15
MPH WITH GUSTS TO 25 MPH NEAR SEWARD AND WHITTIER AFTER MIDNIGHT.
.THURSDAY...MOSTLY CLOUDY. HIGHS IN THE LOWER 20S TO LOWER 30S.
NORTH TO WEST WIND 10 TO 15 MPH WITH GUSTS TO 25 MPH NEAR SEWARD AND
WHITTIER.
.THURSDAY NIGHT...MOSTLY CLOUDY WITH A CHANCE OF SNOW. LOWS 15 TO
25. NORTH TO WEST WIND 10 TO 15 MPH WITH GUSTS TO 30 MPH NEAR SEWARD
AND WHITTIER.


Temperature / Precipitation

SEWARD 35 18 27 / 40 0 0
GIRDWOOD 30 20 27 / 20 0 0


Short Term Weather Model Forecasts (NAM, WRF, GFS) for the Kenai Mountains near Turnagain Pass
Sea-level: GFS shows 0.05 inches of water forecasted today
3000: there is a bubble of above freezing temps that gets real close to Turnagain Pass today, but for the most part, temps are forecasted between 23-32 degrees F with winds 5 mph
6000: temps forecasted between 23 and 32 degrees F with winds 10-20 mph

AVALANCHE DISCUSSION
Todays weather should not contribute to the avalanche danger today at Turnagain Pass.

The main avalanche concern today is that slippery rain crust underneath the 1.5-2.5 feet of newer snow especially between 2000-3000. This slippery rain crust formed on Thursday Jan 7 and is widespread on all aspects from Girdwood to Seward.

For the past 3 days we have been digging and testing the snow at Tincan, Sunburst, and above the snowmachine uptrack on Repeat Offender. The rain crust has looked different at all three locations, but there has been one common feature at all locations. I keep getting the new snow to fail about inch above the top rain crust with hard failures in the lower 20 range on compression tests with clean shears (Q2) where the shear plane is smooth but does not slide readily. According to the text books, this generally indicates good stability (in these particular test pit locations) but a compact group of skiers/snowboarders, a snowmachine, or explosives may trigger an avalanche. Natural avalanches are rare.

These test scores, however, are on the low end of good stability and the structure of the snowpack is poor right now because it has the three main ingredients for an avalanche: a slab on top of a weaker layer of snow on top of a slippery bed surface. Its a little bit alarming that we have been finding the same results at three different mountains. This could indicate that this weak snow immediately above the crust is widespread across Turnagain Pass; which, makes sense based on the snowpack history from the last two weeks.

Actual data is always better for making decisions than opinions; but, for whatever it is worth, Im not willing to risk my life on big terrain when the stability is on the low end of good. I like to wait till the weak layers dont react in my snowpits before I ramp my slope angles and get out into steeper terrain. Its going to take at least a couple more days before this weak layer starts to heal itself. The danger level needs to stay at MODERATE until we see some improvement.

On a side noteOne of our observers took a closer look at those Tincan human-triggered avalanches (see photo gallery). He said they were surface snow slabs only a couple inches deep; so, that means these did not fail on the rain crust. Plus there are some rotten facets underneath the crust in some spots, but we have not found enough consistency or failures with this weak layer to say its a major problem yet.

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 tomorrow Thursday January 21st.


 Show the Complete North American Avalanche Danger Scale
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.

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
© 2019 Chugach National Forest Avalanche Information Center. All rights reserved.
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