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Issued
Tue, March 27th, 2012 - 7:00AM
Expires
Wed, March 28th, 2012 - 7:00AM
Forecaster
Graham Predeger
Avalanche risk The Bottom Line

Good morning. This is Graham Predeger with the Chugach National Forest Avalanche Information Center on Tuesday, March 27th 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 MODERATE today for the core advisory area. Human-triggered avalanches will be possible due to a variety of buried weak layers in our upper snowpack along with fresh wind slabs.

AVALANCHE DISCUSSION

We haven’t seen any large avalanches recently in our forecast area but there have been several class 1 and 2 slides on all aspects. These have not been large and destructive snow slides though many are big enough to bury, injure or kill a person. The common denominator with these avalanches is proving to be buried weak layers (surface hoar and facet/ crust combinations) persisting in the upper snowpack.

Concern #1 – Wind Slabs and Soft Slabs

Winds appear to have picked up again overnight blowing in the 20 to 40 mph range from the east and southeast. Expect to find tender wind slabs on west and northwest aspects especially below ridges today. These newest of wind slabs are likely not bonding well to underlying layers yet. Yesterday we found anCNFAIC Staff sun crust on solar aspects and sporadic pockets of surface hoar. These future weak layers were being buried by light snowfall and are now overlain by a fresh wind slab in problem areas.

Concern #2 – Persistent Slabs

Several weak layers have been buried over the previous 2 weeks. Some of these have healed up nicely and are of no concern today. CNFAIC Staffs however are lingering, waiting for a trigger. It is worth the time to dig into a slope you intend to ski or snowmachine and try to identify the presence of weak layers. An obvious weak layer will show itself as a uniform grey line in your snowpit wall. These weaknesses and overlying slabs have been found recently, lurking in our snowpack from Girdwood to Summit Lake.

Concern #3 – Wet sluffing

It’s unlikely we will see much direct sunlight over the next several days but daytime temperatures do appear to be rising as we near April. Wet sluffs, when initiated will have the potential to step down and pull out some of these deeper buried weak layers over the coming days. Pay attention to areas where the surface won’t support your weight as you step off your skis or machine. This is an easy test that is indicative of the upper snowpack weakening, if you are able to post-hole up to your mid-thigh or crotch.

MOUNTAIN WEATHER

Sunday’s bluebird day gave way to clouds and light precipitation over south central Alaska yesterday. It was snowing lightly most of the day from Girdwood to Turnagain pass with just a few inches of accumulation to cover up some of the most recently deposited surface hoar from the weekend.

With a warmer unsettled air mass digging in, we can expect mostly cloudy skies and gusty east and southeast winds in the 25-40 mph range at ridge top levels today. Precipitation looks to be mainly in the form of snow (1-3″), but may be mixed with rain at lower elevations. Overnight, temperatures will be significantly warmer (high 20’s) than we have seen recently.

CNFAIC Weather Page and the NWS forecast

Kevin will issue the next advisory Wednesday 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.

Tue, March 27th, 2012
Alpine
Above 2,500'
2 - Moderate
Avalanche risk
Treeline
1,000'-2,500'
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
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.