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Issued
Sat, January 8th, 2011 - 7:00AM
Expires
Sun, January 9th, 2011 - 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 Saturday, January 8th 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

The avalanche hazard rating is CONSIDERABLE today. Careful route finding and conservative decision-making are essential in the backcountry. We got more reports of human triggered avalanches yesterday. One was described as a full burial with no reported injuries. These unstable conditions will likely persist through the weekend.

AVALANCHE DISCUSSION

Thanks to all the folks who sent in snow and avalanche observations. It was a solid community effort to compile all that information. Keep this in mind even when conditions are less obvious. Everyone traveling in the backcountry should have some observation worth passing on.

The number and size of recent human triggered avalanches deserves special consideration today. The sunny weekend weather will bring out the crowds, which could cause big problems.

This skier triggered avalanche happened in Warmup Bowl off Seattle ridge on Thursday. It shows the wind distribution of the slab, and exceptional propagation into a large area. I can’t overemphasize how dangerous this can be right now!

CNFAIC Staff human triggered avalanches include: Raggedtop in Girdwood, the burial in Palmer creek (mentioned above), a snowmachine triggered in Seattle creek, and a skier triggered on Seattle ridge. Some CNFAIC Staff slopes that did not release had reported whoomphing and shooting cracks.

See the photo gallery for more examples and a pit profile.

This is not the kind of weak layer/slab that “sets up” and stabilizes soon after the storm. I expect to see a very slow stabilizing trend over time, but continued reactivity into these same weak layers for weeks or months. Conditions right now are different than normal. The way we approach it as backcountry travelers needs to be different as well.

Personally I won’t be traveling in aggressive terrain until we get some significant changes to the snowpack. Time alone won’t heal this setup completely. I think that as travelers increase the slope angles they travel on this weekend we will see more human triggered avalanches. You might ride on the same slope all day, and the 20th person will trigger the whole thing, erasing the old tracks.

Safe travel conditions can be found on lower angle terrain. Today is a great day to keep yourself honest about your own acceptable risk. Pay attention to the slope angles and distribution of the new storm snow. Impose some limits in your travel plan before you start the day and stick to them. The possibility of natural avalanches is low unless a cornice sets off the slab underneath. Human triggers are the main issue right now. Even on flat terrain pay close attention to people traveling on steep slopes above you.

Primary concern: Persistent slab. Don’t expect us to stop talking about these layers anytime soon. The nature of these layers of buried surface hoar and facets is that they stick around for a long time, patiently waiting for the right trigger to release the slope. They are not to be trusted, even long after the last storm. The two most common weak layers responsible for fatal avalanches are buried surface hoar and facets, and we have both right now.

Encyclopedia of avalanche terms.

WEATHER ROUNDUP

The weather we’re concerned about right now already happened. Over 20 inches of new snow and 2.5 inches of water fell during the recent storm. No new snow fell in the last 24 hours. Yesterday a low elevation fog shrouded Turnagain Arm for most of the day, but higher in the mountains was clear and sunny. Expect similar conditions today with temperatures in the 20s. Wind should be light with stronger gusts near Whittier.

Lisa 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 SAT JAN 8 2011

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

HIGHS IN THE LOWER 20S TO LOWER 30S. NEAR SEWARD…NORTH WIND 15 TO

25 MPH. NEAR WHITTIER…WEST WIND 25 TO 35 MPH. VARIABLE WIND TO 10

MPH ELSEWHERE.

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

COOLEST INLAND. NEAR SEWARD…NORTH WIND 10 TO 20 MPH. NEAR

WHITTIER…WEST WIND 20 TO 30 MPH. VARIABLE WIND TO 10 MPH ELSEWHERE.

.SUNDAY…PARTLY CLOUDY. HIGHS IN THE MID 20S TO MID 30S.

VARIABLE WIND 10 MPH EXCEPT NORTH 10 TO 25 MPH NEAR SEWARD.

.SUNDAY NIGHT…MOSTLY CLEAR. LOWS IN THE LOWER 20S TO LOWER 30S.

VARIABLE WIND 10 MPH EXCEPT NORTH 10 TO 25 MPH NEAR SEWARD.

.MONDAY…PARTLY CLOUDY. HIGHS IN THE MID 20S TO MID 30S.

VARIABLE WIND TO 10 MPH. NEAR SEWARD…NORTH WIND 10 TO 20 MPH.

.MONDAY NIGHT…PARTLY CLOUDY. LOWS 15 TO 25.

.TUESDAY THROUGH FRIDAY…PARTLY CLOUDY. HIGHS IN THE 30S. LOWS

15 TO 25.

TEMPERATURE / PRECIPITATION

SEWARD 29 23 32 / 0 0 0

GIRDWOOD 22 18 28 / 0 0 0

WEATHER STATION SUMMARY for Turnagain Pass:

-3800′ Sunburst Wx Station-

Temperatures in the mid 20s. Light wind from the WNW.

-2600′ Seattle Ridge Wx Station-

Temperatures in the low 20s. No wind readings.

-1800′ Center Ridge Wx Station-

Temperatures in the high teens. A couple inches of total snow loss has happened since yesterday due to settling.

Sat, January 8th, 2011
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.