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Issued
Sat, April 10th, 2010 - 7:00AM
Expires
Sun, April 11th, 2010 - 7:00AM
Forecaster
CNFAIC Staff
Avalanche risk The Bottom Line

Good morning backcountry travelers this is Carl Skustad with the Chugach National Forest Avalanche Information Center on Saturday April 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

Skookum Valley and Skookum Glacier are closed to motorized vehicles (snowmachines, helicopters, ATVs) except for subsistence uses.. This closure is directed in the current Chugach National Forest Land and Resource Management Plan. Placer River Drainage remains open for motorized use to Spencer Glacier.

WEATHER ROUNDUP

AnCNFAIC Staff great day yesterday with lots of sun and warm temps. Winds are picking up slightly this morning. The radar shows clear skies at present with a large wave of precip coming in this afternoon. Look for increasing winds and 1-5 inches of snow fall this evening.

AVALANCHE DISCUSSION

Today’s avalanche danger will start out as MODERATE, but will rapidly increase to CONSIDERABLE on any sunny slopes when temperatures go above freezing.

Indications that the sun and warming are increasing the avalanche danger include: point release loose snow avalanches on the slopes you are on or adjacent to, sticky or sun effected surface snow under ski, board, or sled, and the softening of any previous surface crusts. These along with that feeling in your gut that this slope is sunny and hot should tell you to get off of avalanche terrain.

The current surface snow has not yet been tested by significantly warm temperatures. We will see increased avalanche activity whenever the temperatures reach the high 30’s and direct sun is on the slope. We did see lots of point release avalanches again yesterday and some small slabs pop out as a result of the clear skies.

The primary snowpack concern again today is: intense sun and/or warm temps triggering the top 1-3 feet of new snow on top of a buried sun crust on southern aspects. We have 2 out of 3 ingredients necessary for an avalanche:

-A slab (new storm snow)

-A bed surface (slippery sun crust)

The weak layer is the missing ingredient, but that buried sun crust is smooth enough to act as both a bed surface and a weak layer especially if the sun heats up the slab on top.

Glide cracks are secondary concern today. These crevasse like features are those cracks that go all the way to the ground. Avoid traveling underneath these cracks. Glide cracks and full depth release avalanches have been occurring on warm sunny days.

WEATHER FORECAST (National Weather Service)

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKDT SAT APR 10 2010

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

HIGHS IN THE UPPER 30S TO MID 40S. LIGHT WINDS BECOMING SOUTH

TO EAST 10 TO 20 MPH IN THE AFTERNOON…WITH GUSTS TO 30 MPH

THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.

.TONIGHT…A CHANCE OF SNOW IN THE EVENING…THEN SNOW AFTER

MIDNIGHT. SNOW ACCUMULATION 1 TO 4 INCHES. LOWS IN THE MID 20S

TO LOWER 30S. SOUTH TO EAST WIND 10 TO 25 MPH WITH GUSTS TO 35 MPH

THROUGH PORTAGE VALLEY AND TURNAGAIN ARM.

.SUNDAY…SNOW IN THE MORNING…THEN RAIN AND SNOW IN THE

AFTERNOON. SNOW ACCUMULATION 2 TO 6 INCHES. HIGHS IN THE 30S.

SOUTH TO EAST WIND 10 TO 25 MPH WITH GUSTS TO 35 MPH THROUGH

PORTAGE VALLEY AND TURNAGAIN ARM.

.SUNDAY NIGHT…SNOW AND RAIN. LOWS IN THE UPPER 20S TO MID 30S.

SOUTH TO EAST WIND 10 TO 25 MPH.

.MONDAY…SNOW AND RAIN LIKELY IN THE MORNING…THEN A CHANCE

OF RAIN AND SNOW SHOWERS IN THE AFTERNOON. HIGHS IN THE LOWER

TO MID 40S. SOUTH TO EAST WIND 10 TO 15 MPH.

TEMPERATURE / PRECIPITATION

SEWARD 39 32 39 / 0 100 100

GIRDWOOD 39 30 38 / 0 100 100

WEATHER STATION SUMMARY for last 24 hours at TURNAGAIN PASS

3800′-Sunburst Wx Station

20 deg F light wind with moderate SE winds

2600′-Seattle Ridge Wx Station

21 deg F winds are 11 with gusts in the teens

1800′-Center Ridge Wx Station

20 deg F. Total snowpack is 143″

Thanks for checking today’s avalanche advisory. Lisa will update this advisory by 0700 tomorrow morning, April 11th.

Sat, April 10th, 2010
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
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.