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ARCHIVED - Forecasts expire after 24 hours.
Issued
Wed, March 10th, 2010 - 7:00AM
Expires
Thu, March 11th, 2010 - 7:00AM
Forecaster
CNFAIC Staff
Avalanche risk The Bottom Line

Good morning backcountry travelers this is Matt Murphy with the Chugach National Forest Avalanche Information Center on Wednesday March 10th, 2010 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).

ANNOUNCEMENTS

Placer River and Skookum will open to snowmachines today 3/10/2010.

WEATHER ROUNDUP

-The winds have continued to back off since the big storm two days ago. Current average winds speeds are light this morning between 3mph-9mph with light gusts up to 16mph.

-In the last 24 hours (5am-5am), the snotel sites recorded: 0.1 inch of water and 5 inches of snow settlement at Grandview, and 0.0 inches of water and 2 inches snow settlement at Summit Creek, and .3 inches of water and 7 inches of snow settlement in Girdwood Valley.

-The current radar shows some broken precip over Prince William Sound heading toward Cordova, but the Kenai radar is mostly clear.

-Temps have cooled off drastically at all wx stations this morning by 11-18 degrees since yesterday. Current temps are 7 degrees F at sea-level and negative 4 degrees F at 3800′.

AVALANCHE DISCUSSION

Today’s avalanche danger will remain at CONSIDERABLE due to active snow settlement and not enough time since the last major storm, CONSIDERABLE is defined as DANGEROUS avalanche conditions.

We have had a rapid change in temperature in the past 24 hours, and the weather stations are indicating that the snowpack is shrinking or settling fairly quickly. This is common with light density snow following a storm, but it shows that the snowpack is still actively moving and adjusting. Our snowpack still needs some more time before the uncertainty level about avalanches can be reduced.

With that being said, there is some uncertainty in the current snowpack. There were some large natural and artillery triggered avalanches yesterday morning, and we were unable to go to drive south of Girdwood to get any observations from our core advisory area of Turnagain Pass. Except for the weather stations, we have NO DATA from Turnagain Pass for this morning’s report.

Terrain steeper than 35 degrees could potentially be dangerous today. Although the weather has backed off, natural avalanches are still possible today, however, human triggered avalanches are the main danger today. The danger rating of CONSIDERABLE is the most dangerous rating for the human factor. When the avalanche danger is high or extreme, most people do not travel in the mountains. Now that the weather has backed off, this is the time when people start to venture out into the mountains. This is when people’s goals and objectives intersect with unstable snow. Most avalanche fatalities occur when the danger scale reads CONSIDERABLE, just like today. Simply waiting anCNFAIC Staff day or two for the snowpack to adjust could mean the difference between life and death. Don’t get lured into the “I love big dumps” syndrome. Don’t put yourself on steep terrain today.

Secondary avalanche concerns today are glide cracks and cornices. A full depth glide crack release was observed the day before the most recent storm (see photo gallery). Its difficult to say if the new load or the rapid change in temperature will effect these crevasse like features because glide cracks are very difficult to predict. Additionally, its always best to avoid cornices immediatley following a major wind and snow event.

WEATHER FORECAST (National Weather Service)

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST WED MAR 10 2010

…STRONG WIND THURSDAY MORNING THROUGH THURSDAY EVENING NEAR

WHITTIER…

.TODAY…MOSTLY CLOUDY WITH SCATTERED SNOW SHOWERS NORTH OF MOOSE

PASS. PARTLY CLOUDY ELSEWHERE. HIGHS IN THE TEENS. VARIABLE WIND 10

MPH EXCEPT NORTH 10 TO 20 MPH NEAR SEWARD.

.TONIGHT…DECREASING CLOUDS. ISOLATED SNOW SHOWERS IN THE EVENING.

LOWS ZERO TO 5 ABOVE. NORTHWEST WIND 10 TO 15 MPH EXCEPT WEST

20 TO 35 MPH NEAR WHITTIER.

.THURSDAY…MOSTLY SUNNY. HIGHS IN THE TEENS. NORTHWEST WIND 10 TO

25 MPH EXCEPT WEST 30 TO 45 MPH NEAR WHITTIER.

Temperature / Precipitation

SEWARD 17 2 19 / 0 0 0

GIRDWOOD 14 1 17 / 50 20 0

Short Term Weather Model Forecasts (NAM, WRF, GFS) for the Kenai Mountains near Turnagain Pass

Sea-level: temps are forecasted between 1-14 and between 0.0-0.1” of water forecasted

3000′: temps are forecasted in the range of 5 to 14 degrees F with winds 5 mph

6000′: temps are forecasted in the range of (minus 4) to 5 degrees F with winds 5-10 mph

WEATHER STATION SUMMARY for last 24 hours at TURNAGAIN PASS

3800′-Sunburst Wx Station

Current Temp: -4 (18 degrees colder than yesterday)

Winds: In last 24 hours winds have been light to strong averaging 2-36mph with extreme gusts up to 56mph

2600′-Seattle Ridge Wx Station

Winds: In last 24 hours winds have been calm to moderate averaging 0-24mph with an extreme gust of 39mph

1800′-Center Ridge Wx Station

Current Temp: not working

Precip: not working

Thanks for checking today’s avalanche advisory. The next one will be posted tomorrow Thursday March 11, 2010.

Wed, March 10th, 2010
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
3 - Considerable
Avalanche risk
Below Treeline
Below 1,000'
3 - Considerable
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.
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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.