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Issued
Sat, February 11th, 2012 - 7:00AM
Expires
Sun, February 12th, 2012 - 7:00AM
Forecaster
Kevin Wright
Avalanche risk The Bottom Line

Good morning. This is Kevin Wright with the Chugach National Forest Avalanche Information Center on Saturday, February 11th 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

Snow and rain picked up overnight, bringing increased avalanche danger to areas that received the most precipitation and wind. High elevation zones will be CONSIDERABLE with pockets of HIGH avalanche danger. Sheltered areas below treeline, and zones that received less snow and wind will have Moderate to Considerable danger today.

AVALANCHE DISCUSSION

Yesterday we toured into the clouds at Turnagain Pass and found a variable snowpack depending on elevation. At the road level, a moist crust from rain over the last several days was being covered by 5+ inches of new wet snow. As we climbed higher, the crust became harder and slicker with the overlying snow getting lighter, dryer, and looser. At mid elevations there is dry snow on top of a very slick zipper crust, which could prove to be an unstable combination given the right slab ingredients. Above 2000 feet the rain crust disappeared altogether and the snowpack became fairly dry with loose new snow on top of older stiff windboard. We got easy and far running surface sluff to move on steep slopes at 3000 feet, entraining quite a bit of snow on the way down.

Overnight the snowfall has been constant and wind has increased. Much of what we found to be dry and loose yesterday could now be blown into stiffer and cohesive slabs above treeline. We are probably reaching the tipping point where Natural avalanches are becoming likely in some areas, and more snow today will increase those chances.

There is nothing mysterious about the avalanche situation today. Areas with 2 or more feet of fresh snow and high wind will be very prone to natural or human triggered slides. This is a ”Direct Action” situation where ongoing stormy weather is creating rapid snow loading and unstable surface conditions. Areas below treeline, with lesser snowfall amounts and less wind effect will have a lower probability of avalanches.

Primary Concern

Fresh wind slabs and storm snow from the last 24 hours will be easy to trigger in some areas above treeline. Watch for deeper and stiffer pockets near ridgetops and rollovers primarily on West, North, and South aspects.

Secondary concerns

Mid elevation soft slab on top of a slick rain crust. I’m not sure if this will be a problem today, but it has most of the ingredients to be a future issue.

Low elevation wet slab in areas that are still getting rain below 500 feet.

MOUNTAIN WEATHER

The blizzard watch from yesterday has passed, but snow and high wind remain in the forecast. Girdwood valley is reporting more than a foot of snow at mid elevations, approaching 2 feet up high with continued snowfall. Turnagain Pass has received 6-10 inches with wind up to 85mph on Sunburst from the East. Temperatures seem to be increasing at sea level, but decreasing up high. The rain line will be somewhere between 0 and 1000 feet. AnCNFAIC Staff 6-10 inches of snow is forecasted today.

A powerful 953mb low pressure system is just South of the Alaska peninsula. Southcentral Alaska is currently being hit by a front spun off from this Low. There is anCNFAIC Staff storm coming in behind this one, so stormy weather will continue through the weekend and beyond.

CNFAIC Weather Page and the NWS forecast

Wendy will issue the next advisory Sunday morning. If you get out in the backcountry we want to know what you are seeing. Please send us your observations using the button at the top of this page or give us a call at 754-2369. Thanks and have a great day.

Sat, February 11th, 2012
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. 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.