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Issued
Sun, December 26th, 2010 - 7:00AM
Expires
Mon, December 27th, 2010 - 7:00AM
Forecaster
Kevin Wright
Avalanche risk The Bottom Line

Good morning backcountry travelers. This is Kevin Wright with the Chugach National Forest Avalanche Information Center on Sunday, December 26th 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).

BOTTOM LINE

Today the avalanche hazard is LOW, with pockets of MODERATE. Natural avalanches and human triggered avalanches are unlikely. Small human triggered avalanches are still possible in steep upper elevation windloaded terrain. Be on the lookout for pockets of wind slab in isolated areas at upper elevations. Persistent weak layers are widespread through the region, but most areas lack a sufficient slab to cause avalanches.

AVALANCHE DISCUSSION

It doesn’t look like we got the predicted snowfall last night. The major change has been warmer temperatures, mostly at upper elevations. Our trend of clear weather essentially continues, keeping the avalanche hazard on the same trend as before. The primary concern is isolated wind slabs in upper elevation terrain near ridge tops. We’ve had a couple of reports of small wind slabs failing in these areas. In our experience the upper elevation zones are highly variable, from wind scoured slopes to wind loaded slabs, depending on the side of the mountain. If we get more snow today be on the lookout for new windslab.

On Friday we got a third hand report of a skier triggered slab in Goat Couloir above Girdwood. This is the type of terrain we’ve been worried about: high elevation, high consequence, steep, and wind loaded. The report said a 4-6 inch soft slab broke on the second turn down from the cornice at the top of the couloir. The skier was carried a short distance before skiing off the moving slab to the side and recovering. This apparently took all the soft snow out of the run, leaving the rain crust exposed, providing for very challenging skiing to get down the run. Any travelers in expert-only terrain like this should be prepared for little surprises. This area is at 6000 ft, faces SSW and is 45-50 degrees.

The main message is: don’t let your guard down. It’s easy to get complacent when the stability has been so good for so long. Changes are still happening. Use standard safe travel protocol and good judgement in high consequence terrain. The current Turnagain/Kenai snowpack is different than normal (shallower) and more similar to a mid-season Hatcher pass snowpack. It should be treated differently as well. (Typical Turnagain is maritime, deep, dense, and stable snow. Hatcher pass is more intermountain climate with shallow, cold, light density snow with persistent instability.)

For the long term outlook on avalanche conditions: The weather outlook is calling for snow showers through the week, which could make avalanche prediction difficult. If we get small amounts of snow each day spread out over a week’s time the total could be significant, but the stress may be minimal. In general though, these last few weeks of clear and cold have built a weak snowpack. When we get a significant storm it will likely cause dangerous avalanche conditions.

Encyclopedia of terms:

www.fsavalanche.org/Encyclopedia.aspx

WEATHER ROUNDUP

The snow predicted yesterday and last night didn’t materialize in our core advisory area. Radar at 0600 this morning showed snow showers affecting Whittier and light showers over parts of the Kenai. Our weather stations are not measuring any new snow as of this morning. The Weather Service is still predicting 1-4 inches today. Temperatures have come up to the low 20s at the ridge tops. Wind last night was light to moderate, gusting up to 34 on Max’s Mountain.

Jon 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:

INCLUDING…WHITTIER…SEWARD…GIRDWOOD…MOOSE PASS

500 AM AKST SUN DEC 26 2010

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

IN THE AFTERNOON. SNOW ACCUMULATION 1 TO 3 INCHES. HIGHS 5 TO 15

ABOVE EXCEPT IN THE MID TO UPPER 20S ALONG THE COAST. NORTH TO

EAST WIND 5 TO 20 MPH. GUSTS TO 30 MPH NEAR SEWARD IN THE MORNING.

.TONIGHT…PARTLY CLOUDY WITH A CHANCE OF SNOW SHOWERS. LOWS

5 BELOW TO 5 ABOVE EXCEPT IN THE UPPER TEENS TO LOWER 20S ALONG

THE COAST. VARIABLE WIND 10 MPH EXCEPT NORTH 10 TO 20 MPH NEAR

SEWARD. NEAR WHITTIER…WEST WIND INCREASING TO 15 TO 30 MPH

TOWARD MIDNIGHT.

.MONDAY…MOSTLY CLOUDY WITH A CHANCE OF SNOW SHOWERS. HIGHS

IN THE TEENS EXCEPT AROUND 30 ALONG THE COAST. VARIABLE WIND

10 MPH EXCEPT NORTH 15 TO 30 MPH NEAR SEWARD.

.MONDAY NIGHT…MOSTLY CLOUDY WITH A SLIGHT CHANCE OF SNOW

SHOWERS. LOWS 5 BELOW TO 5 ABOVE EXCEPT IN THE LOWER 20S ALONG

THE COAST. VARIABLE WIND 10 MPH EXCEPT NORTH 10 TO 20 MPH NEAR

SEWARD.

.TUESDAY…PARTLY CLOUDY WITH A SLIGHT CHANCE OF SNOW SHOWERS

IN THE MORNING…THEN MOSTLY SUNNY IN THE AFTERNOON. HIGHS

5 TO 15 ABOVE EXCEPT IN THE LOWER TO MID 20S ALONG THE COAST.

LIGHT WINDS EXCEPT NORTH 10 TO 20 MPH NEAR SEWARD.

.TUESDAY NIGHT…MOSTLY CLEAR WITH A CHANCE OF SNOW.

LOWS 5 TO 15 ABOVE.

.WEDNESDAY THROUGH THURSDAY…MOSTLY CLOUDY WITH A CHANCE OF SNOW.

HIGHS 15 TO 25. LOWS 5 TO 15 ABOVE.

.THURSDAY NIGHT…CLOUDY WITH A CHANCE OF SNOW. LOWS IN THE TEENS.

.FRIDAY AND FRIDAY NIGHT…SNOW LIKELY. HIGHS 15 TO 25.

LOWS IN THE TEENS.

.NEW YEARS DAY…CLOUDY WITH A CHANCE OF SNOW. HIGHS 15 TO 25.

TEMPERATURE / PRECIPITATION

SEWARD 26 18 29 / 80 30 30

GIRDWOOD 12 5 18 / 80 20 20

WEATHER STATION SUMMARY for Turnagain Pass:

-3800′ Sunburst Wx Station-

Current temperature 19. Wind to 28 from the NE.

-2600′ Seattle Ridge Wx Station-

21 degrees at 0400. Wind light and variable.

-1800′ Center Ridge Wx Station-

No new snow recorded (yet). Temperatures rising, currently 24 degrees.

Sun, December 26th, 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.
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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.