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Issued
Wed, December 17th, 2008 - 7:00AM
Expires
Thu, December 18th, 2008 - 7:00AM
Forecaster
CNFAIC Staff
Avalanche risk The Bottom Line

GENERAL ANNOUNCEMENTS

Good morning backcountry travelers, this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Wednesday, December 17, 2008 at 7am. This will serve as a general backcountry avalanche advisory issued for the Turnagain Arm (Turnagain Pass is the core advisory area). Local variations always occur. Note: We are now issuing regular advisories 5 days a week Wednesday-Sunday.

A huge THANKS to Alaska Moutain Rescue Group, Alaska Search and Rescue Dogs, Alaska State Troopers, Nordic Ski Patrol, Alyeska Resort Ski Patrol, LifeMed, Anchorage Fire Department and many CNFAIC Staff resources from the Kenai Penninsula and Southercentral Alaska for the rescue training at Turnagain Pass this past weekend. I think everybody learned a lot.

A skier reported several baited traps near the Eddies pullout. We wanted to warn folks with dogs to be careful around this area. Granite Creek, Johnson Pass, Placer, and Twenty Mile are CNFAIC Staff popular trapping areas. Trapping is perfectly legal on the National Forest; but, there are some rules that apply. If you place traps, please mark them so CNFAIC Staff people know where they are and can protect their dogs. If you come accross traps its your responsibility to keep control of your dog and not disturb the traps. Thanks.

MOUNTAIN WEATHER ROUND UP

In the last 24 hours…

-The Center Ridge weather station at 1800 feet in Turnagain Pass-

Recorded zero new precip. Current temperature is 20 degrees F (3 degrees warmer than yesterday morning). Total snowpack depth is 55 inches, with a total of 13 inches of settlement since last Tuesday’s storm.

-Sunburst weather station at 3800 feet in Turnagain Pass-

Recorded light winds averaging 1-14 mph mostly from the east with a moderate gust of 21 mph. Current temperature is 20 degrees F (3 degrees warmer than yesterday)

-Surface Analysis Maps-

From 3 am Tuesday to 9pm last night, These maps have not shown any big storms heading our way. There is a bunch of stuff stirring around and a weak low pressure just to our south.

-Jet Stream-

The analysis from 9pm last night showed the main flow streaming from north to south over Southeast Alaska. The forecast predicts shift over the next 5 days, where it will flow west to east but way to our south. It is predicted to aim at the lower 48.

-Satellite-

As of 6:00 am this morning… it looks pretty boring. It does not look like there is anything over us worth talking about.

-Radar-

The Middleton radar shows nothing. The Kenai radar shows some light precip moving toward Homer.

-General Weather Observations-

Temps are warmer today above 1000 feet (Hwy elevation at the Pass)and colder below that elevation. Winds have been very calm in the past 24 hours.

PRIMARY AVALANCHE CONCERNS

-Terrain Management

-Shallow Snow

-Chocolate Chip Rocks

-Cliff Bands

-October Facets

-Buried Surface Hoar

AVALANCHE AND SNOWPACK DISCUSSION

Here’s the facts…

The following list is a recent timeline of avalanche activity

-Those October facets on the ground failed during the height of the storm last Monday and Tueday (12/8-9/2008)creating large natural avalanches (class 3) on multiple aspects during this past storm.

-Big terrain with large bowls near wind scoured ridges seemed to produce the largest natural avalanches during the storm.

-Artillery was able to trigger some large avalanches last Wednesday (12/10/08) afternoon.

-A snowmachine-triggered avalanche occured last Thursday (12/11/08)

-Some skiers remotely-triggered a class 2 avalanche near some rocks in Goldpan on Saturday (see photo gallery)

-A skier was completely buried 5-6 feet deep on Saturday on the southern aspect of Cornbiscuit (see photo gallery), but was rescued by the quick and knowledgable response of her companions. GREAT JOB EVERYBODY!

-Several people reported hearing “whumphing” and feeling the snowpack collapse around Magnum and Cornbisuit over the weekend.

-Tender small windslabs and wind hammered snow was reported on Pyramid near Turnagain Arm.

Since last week’s storm, people have been skiing/snowboarding/snowmachining all over the place. There were even tracks down Tincan Proper! Lisa and I went up to Seattle Ridge looking for the snowmachine-triggered avalanche. We are trying to find a common factor with the recent avalanche activity. We looked in Main Bowl, Mama’s Bowl, and Stock Run Bowl but did not see any avalanches. We dug some pits. Lisa dug in a similar location where she dug a pit a couple weeks ago to compare/contrast info. I was really interested in shallow snow; so, I found a shallow spot about 3 feet deep and did some compression tests. Every pit we have dug this year has looked pretty similar. There are sugary facets on the ground with a layer of buried surface hoar on top of those facets. Those are the two main weak layers in the snowpack right now and they have a slab of denser snow on top that ranges in thickness of 1-6 feet. Our compression tests yesterday were unable to make those facets or buried surface fail until we whaled on our shovels, and the failure shear was still only a Quality 2 (very clean but not fast). The slab did not pop off the isolated column.

The snowpack has settled 13 inches since last Tuesday, there has been zero new precip since 12/10/08, and winds have been light.

The right kind of trigger on the right kind of terrain can still create small isolated avalanches. Even small avalanches can bury or kill a person. The most likely place for a human-triggered avalanche will remain on shallow snow, near chocolate chip rocks, near cliff bands, or on shallow complex terrain.

Dangerous avalanche conditions still exist on some terrain features. Evaluate the snow and terrain carefully and use good travel habits. Shallow snow seems to be where most of the human-triggered avalanche activity is happening. We still do not have our thick Alaskan snowpack that we have in the spring. If you still see alders, you know the total snowpack is still shallow. Let’s stay away from big lines and complex terrain.

WATCH OUT SITUATIONS

-Rocky terrain with shallow snow connected to deeper snow (photo gallery)

-Steep rollovers (photo gallery)

-If you hear any “whumpfing” or feel any collapsing, then get to safe terrain immediately and call it a day.

WEATHER FORECAST

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST WED DEC 17 2008

.TODAY…INCREASING CLOUDS. HIGHS IN THE 20S. VARIABLE WIND 10 MPH.

.TONIGHT…MOSTLY CLOUDY. ISOLATED SNOW SHOWERS AFTER MIDNIGHT. LOWS

IN THE UPPER TEENS TO MID 20S. LIGHT WINDS.

.THURSDAY…MOSTLY CLOUDY WITH SCATTERED SNOW SHOWERS. HIGHS IN THE

MID 20S TO LOWER 30S. LIGHT WINDS.

.THURSDAY NIGHT…CLOUDY WITH SCATTERED SNOW SHOWERS. LOWS IN

THE 20S. VARIABLE WIND 10 MPH.

.FRIDAY…SNOW LIKELY. HIGHS IN THE UPPER 20S TO MID 30S. EAST WIND

10 TO 20 MPH. NEAR SEWARD…SOUTH WIND 15 MPH BECOMING VARIABLE IN

THE AFTERNOON.

TEMPERATURE / PRECIPITATION

SEWARD 25 22 31 / 0 20 40

GIRDWOOD 24 24 27 / 0 0 40

Wed, December 17th, 2008
Alpine
Above 2,500'
0 - No Rating
Avalanche risk
Treeline
1,000'-2,500'
0 - No Rating
Avalanche risk
Below Treeline
Below 1,000'
0 - No Rating
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
Travel Advice Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches Natural and human-triggered avalanches unlikely. Natural avalanches unlikely; human-triggered avalanches possible. Natural avalanches possible; human-triggered avalanches likely. Natural avalanches likely; human-triggered avalanches very likely. Natural and human-triggered avalanches certain.
Avalanche Size and Distribution Small avalanches in isolated areas or extreme terrain. Small avalanches in specific areas; or large avalanches in isolated areas. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. Large avalanches in many areas; or very large avalanches in specific areas. Very large avalanches in many areas.
Observations
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Date Region Location
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02/20/24 Turnagain Avalanche: Tincan
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02/19/24 Turnagain Avalanche: Base of Seattle Ridge
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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.