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Issued
Sun, December 5th, 2010 - 7:00AM
Expires
Mon, December 6th, 2010 - 7:00AM
Forecaster
CNFAIC Staff
Avalanche risk The Bottom Line

Good morning backcountry travelers this is Lisa Portune with the Chugach National Forest Avalanche Information Center on Sunday, December 5th at 7am. 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

Carl Skustad, the Director of the Chugach National Forest Avalanche Information Center, has accepted a promotion and will be moving with his family to Minnesota. Carl created this avalanche center and his leadership will be missed. The Skustads have been an important part of the Girdwood community for over 10 years. Thanks Carl for all your good work here on the Chugach!

WEATHER ROUNDUP

It was a beautiful day of perpetual alpenglow yesterday after 8-14 inches of new snow fell in Turnagain Pass 2 days ago. After the gale force winds on Friday, ridgetop winds yesterday averaged 5-15mph out of the east while mountain temperatures ranged from the upper teens to low 20’s. Skies are partly cloudy this morning with mountain temps in the 20’s and light ridgetop winds. Today temperatures will be just slightly warmer than yesterday while winds should remain on the light side as well.

AVALANCHE DISCUSSION

Today the avalanche hazard will remain at CONSIDERABLE on steep windloaded slopes greater than 38 degrees while slopes not affected by Friday’s wind will have a MODERATE danger. Small to medium sized human-triggered avalanches 1-2 feet deep will certainly be possible on steep windloaded terrain. Use extra caution on steep unsupported convex slopes near ridgetops and in crossloaded gullies.

Friday’s storm dumped 8-14 inches of surprisingly light dry snow on top of a layer of surface hoar that formed last week during the clear and cold weather. Underneath the surface hoar is 6 inches of low density faceted snow, which in turn is sitting on the dreaded Thanksgiving Rain Crust. We saw numerous small natural avalanches on the west face of Eddies and on the north side of Cornbiscuit that probably happened at the tail end of the storm. As Jon and I toured up Tincan yesterday we got collapsing and cracking of the snowpack on wind-affected terrain above treeline…sure signs of instability. On a small 40 degree test slope at 2500 feet, I triggered a shooting crack 25-30 feet long and 1.5 feet deep that coincided with 2 loud whumphs. The soft windslab failed on the layer of surface hoar 6 inches above the crust. Several snowmachiners also reported triggering small avalanches on steep rollovers.

The persistent nature of buried surface hoar and rain crusts warrants careful route finding skills and conservative decision making about what slopes to ski and ride. The new snow in non wind-affected terrain is not slabby enough yet to propagate a fracture, so our primary concern today is mainly on windloaded slopes. For the first time in 4 weeks, I saw no new glide avalanches up at the pass yesterday. The new snow is covering up many of the existing cracks that have not avalanched yet, so be extra cautious on your descent.

On a side note, we received a report of several human triggered avalanches in the South Fork area north of Anchorage. A skier in North Bowl ski cut an east facing gully at 3800 feet and triggered a slide 12-18 inches deep that ran 600 feet downhill. As he began to ski cut, he heard a “pop” just before the entire slope broke under his skis and about 20 feet above him. He was able to ski off of the slab but his dog was swept down slope. Fortunately his dog was not buried. CNFAIC Staff human triggered avalanches were spotted on Three Bowls and Lynx yesterday as well.

I will issue the next advisory tomorrow morning at 7am. If you get out in the backcountry give us a call at 754-2369 or send us your observations using the button at the top of this page. Thanks and have a great day.

The NWS weather forecast for:

WESTERN PRINCE WILLIAM SOUND-

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST SUN DEC 5 2010

.TODAY…MOSTLY CLOUDY WITH SCATTERED SNOW SHOWERS IN THE

MORNING…THEN PARTLY CLOUDY IN THE AFTERNOON. HIGHS IN THE LOWER

20S TO MID 30S…COOLEST INLAND. VARIABLE WIND TO 10 MPH. NEAR

SEWARD…NORTH WIND 10 MPH INCREASING TO 20 MPH IN THE AFTERNOON.

NEAR WHITTIER…WEST WIND 10 MPH INCREASING TO 20 MPH BY AFTERNOON.

.TONIGHT…MOSTLY CLEAR. LOWS IN THE LOWER TEENS TO LOWER

30S…COOLEST INLAND. VARIABLE WIND TO 10 MPH. NEAR SEWARD…NORTH

WIND 10 TO 25 MPH. NEAR WHITTIER…WEST WIND 20 TO 30 MPH.

.MONDAY…MOSTLY CLOUDY WITH SCATTERED SNOW SHOWERS. HIGHS IN THE

LOWER 20S TO MID 30S…COOLEST INLAND. LIGHT WINDS. NEAR

SEWARD…NORTH WIND 15 TO 25 MPH. NEAR WHITTIER…WEST WIND 20 TO 30

MPH.

TEMPERATURE / PRECIPITATION

SEWARD 32 26 33 / 40 20 40

GIRDWOOD 24 18 24 / 0 20 40

WEATHER STATION SUMMARY for Turnagain Pass:

-3800′ Sunburst Wx Station-

recorded light easterly winds yesterday averaging 5-15mph and temps ranging from 16F to 20F. The current temp is 20F with light winds out of the northeast.

-2600′ Seattle Ridge Wx Station-

stopped working yesterday but recorded temps ranging from 19F to 23F. The current temp is 24F.

-1800′ Center Ridge Wx Station-

recorded no new snow in the last 24 hours. Temps yesterday ranged from 20F to 24F. The current temp is 25F.

Sun, December 5th, 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. 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.