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Issued
Wed, February 29th, 2012 - 7:00AM
Expires
Thu, March 1st, 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 Wednesday, February 29th 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 danger is LOW with pockets of MODERATE this morning. Be aware of likely sluffing in steep terrain. Most areas with slope angles less than 35 degrees will have a LOW avalanche danger.

AVALANCHE DISCUSSION

Our most recent storm that ended Monday morning refreshed the surface conditions nicely, and seems to be stabilizing quickly. With good visibility yesterday we were able to get a more comprehensive survey of the natural avalanche cycle. A few larger slab avalanches were seen in the region, but generally the mountains held together. The more typical problems associated with the last few days continue to be loose snow sluffing in steep terrain and large cornice failures. In a handful of places the sluffs and cornices were able to pull slabs underneath.

The snowpack continues to have only minor near-surface problems. The storm on Sunday/Monday fell on top of well developed stellar crystals that have a similar (but less persistent) weak layer effect as buried surface hoar. The worst case scenario today is finding an area of stiffer (~1 foot deep) wind slab on top of those loose stellars where it might have the ability to propagate into a larger slab. Based on what we saw yesterday this is not likely, but could be possible on very steep wind loaded terrain. Our test pits yesterday showed moderate but clean failure on this layer, with no propagation in an extended column test.

The more likely avalanche problem today will be in the form of loose point releases. Check out Wendy’s observation from yesterday. The top 4 inches of surface snow is very loose, and will fall away easily on steep terrain in a sluff avalanche. The volume and mass from these was small to medium in size, and manageable if expected.

MOUNTAIN WEATHER

Yesterday was a mostly sunny and calm day in the mountains. There has been no additional snow accumulation in 48 hours. Some afternoon sun exposure produced minor surface melting on direct South aspects.

Snow is possible for the rest of the week, but the pattern is generally weak for precipitation. Today’s forecast calls for 2-4 inches of snow with minimal wind. Unless snow accumulations are greater than the prediction, today’s weather should not affect avalanche conditions very much.

CNFAIC Weather Page and the NWS forecast

Wendy will issue the next advisory Thursday 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.

Wed, February 29th, 2012
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. 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.