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ARCHIVED - Forecasts expire after 24 hours.
Issued
Wed, February 24th, 2010 - 7:00AM
Expires
Thu, February 25th, 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 February 24th 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).

WEATHER ROUNDUP

-The winds have been and are currently light at all ridge top weather stations

-The current radars are mostly clear except for some very light precip moving west to east over the Kenai Penninsula

-In the last 24 hours (5am-5am), the snotel sites recorded 0 inches of water at Turnagain Pass, 0 inches at Grandview, and 0 at Summit Creek. The total snowpack has settled 1-2” since yesterday

-Temps are about the same this morning compared to yesterday. Temps range from 33 degrees F at sea-level and 24 degrees F at 3800′

AVALANCHE DISCUSSION

Today’s avalanche danger will decrease to LOW with pockets of MODERATE due to adequate time since the last major avalanche cycle and the insignificant weather forecast.

The pockets of MODERATE where heightened avalanche awareness is advised are:

-Cornices

We received a report of a close call that happened on Monday 2/22/2010 on the cornice above Zero Bowl (No Name Bowl) at the top of the snowmachine up-track on Seattle Ridge. A snowmachiner accidently triggered a chunk of cornice that fractured underneath the ski of his snowmachine. We took a closer look at the cornices along Seattle Ridge yesterday 2/23/2010 from 3000′ in Warm-Up Bowl to 2400′ in Main Bowl near Widowmaker. We found: several cornice failures, cracks at the roots of cornices that are difficult to see but easy and dangerous to fall into, sagging cornices, and generally much larger cornices than we have seen all year. Be especially careful along ridges with cornices today.

-Glide Cracks

Glide cracks are those crevasse like features in the snow that open up all the way to the ground. The snowpack is starting to pull away from the ground in many locations creating these glide cracks. Glide cracks are very difficult to predict. Sometimes they avalanche when it is cold, sometimes when it is warm, sometimes when it rains, sometimes when it snows. The point is that we are having an active glide crack cycle right now. At least one glide crack avalanche was observed yesterday 2/23/2010 below 2000′ on Center Ridge. When glide cracks avalanche, they fail all the way to the ground. We also observed a dirty pile of debris on a northern aspect on Tincan Ridge (beyond Todd’s Run). We were not able to see the origin of that dirty pile, but there is a good chance that it was a glide crack avalanche as well. Avoid traveling underneath or anywhere near glide cracks especially during times that they are actively moving like they are right now.

Glide cracks and cornices are total wild cards. Both of these features are very difficult to predict. Since we are seeing recent activity with both of these features right now, this is one of those times to be extra careful anywhere near these feature. Avoid traveling underneath, along the side, or above, or anywhere near these features.

WEATHER FORECAST (National Weather Service)

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST WED FEB 24 2010

.TODAY…MOSTLY CLOUDY. ISOLATED RAIN AND SNOW SHOWERS IN THE

MORNING. HIGHS IN THE 30S. LIGHT WINDS.

.TONIGHT…PARTLY CLOUDY. LOWS IN THE LOWER 20S TO LOWER 30S…

COLDEST INLAND. LIGHT WINDS.

.THURSDAY…MOSTLY CLOUDY WITH A CHANCE OF SNOW IN THE AFTERNOON.

HIGHS IN THE UPPER 20S TO MID 30S. LIGHT WINDS.

Temperature / Precipitation

SEWARD 37 28 35 / 20 0 0

GIRDWOOD 37 25 34 / 0 0 30

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

Sea-level: temps are forecasted between 25-37 and between 0.0”-0.1” of water forecasted 3000′: temps are forecasted in the range of 23-32 degrees F with winds 5 mph

6000′: temps are forecasted in the range of 23-32 degrees F with winds 5-10 mph

WEATHER STATION SUMMARY for last 24 hours at TURNAGAIN PASS

3800′-Sunburst Wx Station

Current Temp: 24 (same as yesterday)

Winds: currently averaging light at 3mph with light gusts up to 4mph

In last 24 hours winds averaged light 1-11mph with light gusts up to 16mph

2600′-Seattle Ridge Wx Station

Winds: currently averaging light at 2mph with light gusts to 4mph

In last 24 hours winds averaged light 2-15mph with a moderate gust of 25mph

1800′-Center Ridge Wx Station

Current Temp: 30 degrees (2 degrees colder than yesterday)

Precip: 0 new water, 0 new snow, 2” of total snowpack settlement/melting for total snowpack depth of 89”

Thanks for checking today’s avalanche advisory. The next one will be posted tomorrow Thursday February 25th.

Wed, February 24th, 2010
Alpine
Above 2,500'
1 - Low
Avalanche risk
Treeline
1,000'-2,500'
1 - Low
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
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.