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ARCHIVED - Forecasts expire after 24 hours.
Issued
Wed, December 10th, 2008 - 7:00AM
Expires
Thu, December 11th, 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 10, 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.

INTERAGENCY AVALANCHE RESCUE TRAINING

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

MOUNTAIN WEATHER ROUND UP

In the last 24 hours…

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

Recorded 1.0 inch of water and 8 inches of new snow. Current temperature is 21 degrees F (8 degrees colder than yesterday morning). Total snowpack depth is 68 inches. **STORM TOTALS IN PAST 48 HOURS ARE 2.4 inches of water and 27 inches of new snow**

-Grandview weather station at 1100 feet along the AK Railroad Tracks-

Recorded 2.6 inches of water and 30 inches of new snow in the past 48 hours.

-Sunburst weather station at 3800 feet in Turnagain Pass-

Recorded moderate to light winds averaging 1-23 mph out of the East with a strong gust of 35 mph. Current temperature is 21 degrees F (2 degrees colder than yesterday)

-Surface Analysis Maps-

From 3 am Tueday to 3 am today, the storm that has been dumping on us for the past 2 days parked itself south of Prince William Sound and got much weaker (960Mb-991Mb).

-Satellite-

As of 6:00 am this morning, I can’t really see anything worth talking about on the Satellite.

-Radar-

The Middleton radar is still down, but the Kenai radar is working. It shows light precip over the Anchorage Bowl and Chugach State Park.

-Jet Stream-

The analysis from 9pm last night showed the main flow going west to east heading right towards southern British Columbia. The forecast predicts it will stay the same today, but might shift to a north to south flow in 36-48 hours.

-General Weather Observations-

Temperatures are colder this morning than yesterday by 1-9 degrees at all weather stations from sea-level to 3000 feet. Winds have calmed down at the ridgetops this morning.

PRIMARY AVALANCHE CONCERNS

-New storm snow

-October facets on the ground

AVALANCHE AND SNOWPACK DISCUSSION

The storm that has been dumping on us for the past 48 hours put the biggest load of new weight the our snowpack has had all year. Anytime you have a drastic or rapid change like this, you can expect natural and human triggered avalanches. Our main concern before this storm was that layer of facets on the ground that formed in October. Now, we have a lot more weight on top of that weak layer. Today, the biggest avalanche concern will be new storm snow. There will be potential for large avalanches.

Lisa and I decided not to hike at Turnagain Pass yesterday due to avalanche hazard. One of the best ways to stay alive in avalanche terrain is to follow a strict adhearance to the 24 rule. 90% of avalanche accidents/fatalities occur during storms or 24 hours following a storm. Don’t put yourself in that situation.

We received an observation from Tincan yesterday (Thank Nathanael). This party reported stability tests with a rutsch block that failed on the first jump and stepped down to the October facets. Their isolated column sheared with a score of 18 1.5 feet deep. One member also remotely triggered a small 100-150 foot wide, 1.5 foot deep storm slab, that ran 300 feet.

Traveling on or near slopes steeper than 30 degrees in the backcountry is not recommended today. Go ski/snowboard at Alyeska. They opened Christmas Chute and the Knuckles yesterday, I heard it was awesome. If you snowmachine today, stay far away from any steep slopes. Let’s let this snow adjust to the mountains.

WEATHER FORECAST

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST WED DEC 10 2008

.TODAY…SNOW IN THE MORNING…THEN SNOW SHOWERS IN THE

AFTERNOON. SNOW ACCUMULATION 1 TO 6 INCHES…HIGHEST AMOUNTS NORTH OF

SEWARD. HIGHS IN THE UPPER 20S TO MID 30S. VARIABLE WIND 5 TO 15 MPH.

SEWARD…NORTH WINDS 15 MPH BECOMING SOUTH IN THE AFTERNOON.

.TONIGHT…MOSTLY CLOUDY WITH ISOLATED SNOW SHOWERS. LOWS IN THE

UPPER TEENS TO MID 20S. NORTH TO WEST WINDS 10 TO 20 MPH.

.THURSDAY…PARTLY CLOUDY. ISOLATED SNOW SHOWERS. HIGHS IN THE 20S.

NORTH TO WEST WINDS 10 TO 25 MPH.

TEMPERATURE / PRECIPITATION

SEWARD 36 23 27 / 60 0 0

GIRDWOOD 31 21 24 / 100 60 0

Wed, December 10th, 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.
Observations
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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.