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Turnagain Area Avalanche Advisory
Wednesday, January 13th 2010 7:17 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 13th 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).

ANOUNCEMENTS
Thanks to the group that removed the snowmachine jump structure on the motorized side of the highway so quickly.

WEATHER ROUNDUP
Hindcast (Last 24 hours)

3800 -Sunburst Wx Station-
Temperatures ranged between 18 to 23 degrees F with light to moderate average winds between 7-17 out of the E with a strong max gust of 27 mph
Current temp is 23

2400-Seattle Ridge Wx Station-
Winds have been light to moderate averaging 1-22 mph out of the SE with a strong max gust of 30mph

1800-Center Ridge Wx Station-
Precip: 0.3 inches of water and 7 of new snow *(see parking lot totals for ground truth snow depths from yesterday. This weather station was a bit behind in reporting snow depths yesterday due to the very light consistency of the snow; so, the 7 of blower powder that is recorded today actually represents yesterdays snowfall)
Total depth of 61 inches
Temperatures have increased 20 degrees.
Current temp is 30

Parking lot snow stake measurements taken at 10 am yesterday 1/12/10.
Eddies Lot: 7 new snow
Motorized Lot: 6 new snow
Sunburst Lot: 5 new snow
Johnson Pass North Lot: 3 new snow

Nowcast

Temps have increased at almost all wx stations this morning. Mid elevations around 1800 warmed up by 18-20 degrees, but all CNFAIC Staff weather stations are showing increased temps of 5-9 degrees compared to yesterday morning. Currently, its 21 degrees at sea level and 23 degrees at 3800. Winds have backed off a bit since last night and are currently light at all ridgetop wx stations this morning. Precip totals are consistent at all wx stations with about .3-.4 inches of water and 6-7 of new snow; however, this snow actually fell yesterday based on our ground truths yesterday at Turnagain Pass. The Middleton radar shows moderate precip mostly over Cordova, and the Kenai radar is mostly clear.

Forecast

WESTERN PRINCE WILLIAM SOUND-
INCLUDING...WHITTIER...SEWARD...GIRDWOOD...MOOSE PASS
500 AM AKST WED JAN 13 2010
.TODAY...SNOW LIKELY IN THE MORNING...THEN SCATTERED SNOW SHOWERS
IN THE AFTERNOON. SNOW ACCUMULATION 1 TO 3 INCHES. HIGHS IN THE
MID 20S TO MID 30S. LIGHT WINDS EXCEPT NORTH 10 MPH NEAR SEWARD.
.TONIGHT...MOSTLY CLOUDY WITH SCATTERED SNOW SHOWERS. LOWS IN THE
LOWER 20S TO LOWER 30S. LIGHT WINDS EXCEPT NORTH 10 MPH NEAR
SEWARD.
.THURSDAY...A CHANCE OF SNOW IN THE MORNING...THEN SNOW LIKELY IN
THE AFTERNOON. SNOW ACCUMULATION UP TO 1 INCH. HIGHS IN THE UPPER
20S TO MID 30S. LIGHT WINDS EXCEPT NORTH 10 TO 15 MPH NEAR
SEWARD.

TEMPERATURE / PRECIPITATION

SEWARD 34 24 35 / 60 40 60
GIRDWOOD 29 24 34 / 60 40 50





Short Term Weather Models (NAM, WRF, GFS) for the Kenai Mountains near Turnagain Pass
Sea-level: GFS shows 0.1 inches of water forecasted today
3000: temps forecasted between 23 and 32 degrees F with winds 5 mph
6000: temps forecasted between 23 and 32 degrees F with winds 5 mph

AVALANCHE DISCUSSION
Todays weather should not contribute to the avalanche danger today at Turnagain Pass, but the winds on Seattle Ridge increased last night and may have formed a few small wind slabs because yesterday's 6 inches of light fluffy snow was easy for the wind to transport. The NWS is not calling for any major weather today and the models over Turnagain Pass are only calling for up 0.1 inches of water with light winds; so, todays weather forecast does not look like it will pack too big of a punch.

Todays avalanche danger will remain at LOW with pockets of MODERATE due to small wind slabs near ridgetops, and easily triggered small slabs on steep rollovers at all elevations. LOW is defined as: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Natural and human triggered avalanches unlikely (except glide cracks are possible). Small avalanches in isolated areas of extreme terrain. MODERATE is defined as heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Natural avalanches unlikely, human-triggered avalanches possible. Small avalanches in specific areas; or large avalanches in isolated areas.

In simple terms, we have a variety of weak layers below 3000 and one weak layer at higher elevations between 2800-3800.

The big picture right now is that the rain crust that formed up to 3000 has a lot of potential to become a very dangerous weak layer in the future. Turnagain Pass has plenty of terrain steep enough to avalanche from valley floors up to 3000 including the bowls along Seattle Ridge. Its difficult to say exactly how this rain crust will react to new snow on top; so, we all need to take it easy once the next big storm comes in.

Yesterday, we found that slippery and supportable rain crust at 3000 in Warm Up Bowl on Seattle Ridge. The 6 inches of yesterdays new snow failed very easily starting as sluffs which ran far and easily entraining snow as it plowed down to the valley bottom. There was a little propagation yesterday when the snow was light; so, use elevated caution if you find any stiff wind slabs deeper than a foot today, because this type of slab will avalanche very easily on top of that slippery bed surface. We also were able to easily ski cut lots of small slabs on any steep rollover skiing down Repeat Offender above the snow machine up-track to Seattle Ridge. Lisa and Jon found similar results on Tincan yesterday. The reason the danger level is LOW-MODERATE today is because there is not enough snow on top of the slippery rain crust to create large avalanches. If there was 3 feet of new snow, then avalanche conditions would be deadly today. Things are not looking good for the avalanche danger after the next storm, but it will all depend on how the next storm comes in.

A wild card right now are the glide cracks. One of these crevasse like features avalanched last week for no obvious or apparent reason (see photo gallery). Nostradamus couldnt have predicted that one; so, it adds to the theory that glide cracks are like cornices in that they are very difficult to predict. Sometimes they avalanche when its cold, sometimes when its warm, sometimes when it rains. We have not seen or had any reports of any more glide crack failures in the past week, but it would still be wise to avoid traveling on, near, or underneath the path of any glide cracks.

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 14th.

 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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