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ARCHIVED - Forecasts expire after 24 hours.
Issued
Fri, December 12th, 2008 - 7:00AM
Expires
Sat, December 13th, 2008 - 7:00AM
Forecaster
CNFAIC Staff
Avalanche risk The Bottom Line

GENERAL ANNOUNCEMENTS

Good morning backcountry travelers, this is Carl Skustad with the Chugach National Forest Avalanche Information Center on Friday, December 12, 2008 at 7am. This will serve as a general backcountry avalanche advisory issued for the Turnagain Arm Area (Turnagain Pass is the core advisory area). Local variations always occur.

INTERAGENCY AVALANCHE RESCUE TRAINING

On the weekend of December 13-14, there will be an avalanche rescue training taking place this weekend at Turnagain Pass. Please be aware of rescue workers, helicopters, rescue snowmachines and areas set up for rescue training drills. Thanks.

MOUNTAIN WEATHER ROUND UP

In the last 24 hours…

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

Recorded no new snow. Current temperature is 7 degrees F (9 degrees colder than yesterday morning). Total snowpack depth is 62 inches, with a total of 7 inches of settlement since the storms end Wed.

-Sunburst weather station at 3800 feet in Turnagain Pass-

Recorded moderate NW winds averaging 10-14 mph. Current temperature is 7 degrees F (4 degrees colder than yesterday)

-Surface Analysis Maps-

the remnants of the storm are petering out as a weak low pressure (1022 mb) system passes through today, then two high pressure systems are on tap for the weekend.

-Jet Stream-

The analysis from 9pm last night showed the main flow streaming from west to east and heading right towards Juneau. The forecast predicts shift in the next 24 hours and start flowing from north to south.

-Satellite-

Fairly clear

-Radar-

clear sailing

-General Weather Observations-

Burr, Summit lake is the cold spot this morning with -1 deg. mercury. All CNFAIC Staff stations are in the single digits as well except for Portage (19). Expect ridge top winds today in the teens. Wind direction will prevail out of the NW but will be channeled by local topography.

PRIMARY AVALANCHE CONCERNS

-Terrain Management

AVALANCHE AND SNOWPACK DISCUSSION

A snowmachine triggered avalanche in either Mama’s or Main bowl yesterday (see our map page for location). The rider went for a ~500 foot ride while his sled stayed up on the crown. Not a lot of info on this but he was buried up to his chest after deploying his ABS airbag backpack. If you were involved with this ride please contact us. Glad everyone was alright. Don’t count on the technology to save your butt every time. Get educated and make good decisions. Managing terrain will be the name of the game this weekend. There will be clear skies and lots of blower powder. The avalanche I just described failed 2 feet deep. This is new storm snow on old snow. Matt and I tested this interface yesterday on Sunburst and found moderate to hard test results. CT22 Q2 70cm. This type of weak layer will tighten up over the next couple of days, but obviously still has potential to take you for a ride. Alex found less new snow at Summit Lake but weaker snow stability scores. I expect Summit and Lost Lake to have a slightly higher avalanche hazard than Turnagain this weekend, do to a shallower snowpack and windier conditions leading to wind slab formations on southern and eastern aspects. We also found the buried layer of surface hoar 5 feet deep. You can still see it with the naked eye, but test resulted in hard sheers. CT30+ Q2 160cm

Here’s the facts…

-Those week October facets failed on multiple aspects during this past storm.

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

-Artillery was able to trigger some large avalanches yesterday afternoon.

-The snowpack has settle 7 inches in the past 48 hours, temps have cooled down, winds have been moderate.

Matt, asked the question yesterday “can we still humanly trigger avalanches”, the answer is yes. You can still find the avalanche dragon lurking on actively loading leeward slopes, in shallower snow near rock bands and on scoured ridges. Keep your slope angles less than 38 deg and reduce exposure to complex terrain and you can enjoy great blower powder.

WATCH OUT SITUATIONS

-Rocky terrain with shallow snow connected to deeper snow

-Steep rollovers (check out the photo gallery picture of Mangum)

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST FRI DEC 12 2008

.TODAY…MOSTLY SUNNY IN THE MORNING THEN BECOMING MOSTLY CLOUDY.

HIGHS IN THE MID TEENS TO LOWER 20S. NORTH AND WEST WIND 10 TO 20 MPH

WITH GUSTS TO 35 MPH NEAR WHITTIER AND SEWARD.

.TONIGHT…DECREASING CLOUDS. LOWS 5 TO 15 ABOVE. NORTH AND WEST WIND

10 TO 25 MPH WITH GUSTS 35 MPH NEAR WHITTIER AND SEWARD.

.SATURDAY…SUNNY. HIGHS IN THE MID TEENS TO LOWER 20S. NORTHWEST

WIND 10 TO 20 MPH. GUSTS TO 35 NEAR WHITTIER AND SEWARD DIMINISHING

IN THE AFTERNOON.

.SATURDAY NIGHT…MOSTLY CLEAR. LOWS 5 TO 15 ABOVE. NORTH WIND

15 MPH.

.SUNDAY…SUNNY. HIGHS IN THE UPPER TEENS TO MID 20S. LIGHT

WINDS.

.SUNDAY NIGHT…MOSTLY CLEAR. LOWS IN THE TEENS.

TEMPERATURE / PRECIPITATION

SEWARD 23 17 27 / 0 0 0

GIRDWOOD 18 5 16 / 0 0 0

Fri, December 12th, 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. Dangerous avalanche conditions. 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.
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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.