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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Tuesday, March 11th 2014
Created: Mar 11th 5:48 am
4 High Alpine / Above 2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4 High Treeline / 1,000'-2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4 High Below Treeline / Below 1,000' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
 Show the Complete North American Avalanche Danger Scale
Special Announcement


The Alaska DOT Avalanche Program will be conducting avalanche hazard reduction work on the Seward Highway and Portage Road today - expect delays. Check 511.gov for more details.


The Bottom Line

The avalanche danger is HIGH in the mountains surrounding the Eastern Turnagain Arm. Upwards of 20-24" of snow has fallen since yesterday morning and another 7-10" is on tap for today. Large natural avalanches are likely and human triggered avalanches are certain due to the rapid loading by the new snow and strong Easterly wind. The new snow is falling on a very weak preexisting surface which is expected to enhance avalanche activity. 

AN AVALANCHE WARNING IS IN EFFECT FOR TODAY AND WILL EXTEND THROUGH MIDNIGHT TONIGHT.

**Dangerous avalanche conditions exist in the backcountry. Travel in avalanche terrain is not recommended. This includes all slopes steeper than 30 degrees. Avoid terrain traps, such as gullies and tree wells and steer well clear of runout zones.

Avalanches may be triggered remotely from the side, top or from below. Treed locations have many terrain traps that can pose a serious threat today.


Primary Concern

Well, it sure looks like winter is taking a 3rd stab at coming to Southcentral Alaska this season. After a high and dry couple of weeks (not to mention our thin snowpack that sits roughly ~40% of average) we are now entering into a stormy weather pattern. Due to the meager snow year, we have been plagued with several weak layers in the snowpack. The most concerning one for this storm cycle is the preexisting snow surface. Before snow began to fall yesterday, we had a mix of 1-2" of faceted snow and surface hoar sitting on a variable 1-4" crust (for a better look at this check out Fitz's video from Sunday). This is a classic weak layer and bed surface combo that now has a 2-3' slab on top.

During our field day yesterday only 6-8" of snow had fallen yet we were able to find and easily trigger a slab avalanche 10-14" thick on a wind loaded slope (photo below).  This is a look at things to come. With up to 2' of storm snow currently and more on the way, slab avalanches up to 2-3' deep, or deeper in wind loaded locations, are likely. Additionally, the weak snow underneath adds to the potential for slabs to propagate around terrain features and possibly break where you may not expect them to.

Photo: Human triggered slab avalanche in the Tincan Trees, ~1,700' elevation, West facing.

 

For today, avoiding avalanche terrain is recommended due to the high volume of heavy snow sitting on a weak surface. Again, avalanches have the ability to propagate wider than expected and can be triggered remotely; this includes from below. Even "in the trees" avalanche terrain exists and there are dangerous terrain traps under small steep slopes/cliffs.


Mountain Weather

Since 7am yesterday, heavy snowfall has deposited 20+ inches in the mountains around the Eastern Turnagain Arm. Winds were strong from the East with this "Chugach Special" and averaged in the 50-70mph range with a max gust at the Sunburst station of 114mph! Snowfall has tapered off overnight along with the Easterly winds, which are now blowing 20-30 with gusts to 50mph. The rain/snow line crept up from sea level to around 1,000' overnight along with the ridgetop temperatures which have risen from ~20F to the mid 20'sF.

Storm totals (7am yesterday to 6am today - check this out on the Turnagain Pass snow stake loop!):
Turnagain Pass, 1880' elev - 20" snow (1.6" water equivalent)
Girdwood Valley, 1700' elev - 21" snow (1.6" water equivalent)
Summit Lake, 1400' elev - 8" snow (.6" water equivalent)

An additional 7-10" of snow (~.7" water) is on tap today as the remnants of the large low pressure system continues to spin South of the Kenai pushing moisture our way. The Easterly winds are also expected to bump back up today into the 50mph range with higher gusts. Temperatures are expected to remain in the mid 20'sF on the ridgelines and the rain/snow line hover near 1,000'.

Looking forward: The weather models are showing a break in storms late tonight through Wednesday before another - and very similar - low pressure tracks through Thursday/Friday. This should bring another decent shot of precip our way.

 

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).

Winter snowmachine use open/closed status and riding conditions updates

Riding status is not associated with avalanche danger. An area will be open to motorized use in accordance to the Forest Management Plan when snow coverage is adequate to protect underlying vegetation. Backcountry hazards including avalanche hazard are always present regardless of the open status of motorized use areas.

(Updated: Nov 18, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedOnly a few inches of snow sits at the motorized lot, not enough to open for snowmachining at this time. Updated Nov. 18, 2017
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail is expected to open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
Summit Lake: Closed

Subscribe to the Turnagain Area Avalanche Advisory:

The information in this advisory is from the U.S. Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur. This advisory provided by the Chugach National Forest, in partnership with Friends of the Chugach National Forest Avalanche Information Center.


USFS SNOW AND AVALANCHE HOTLINE (907) 754-2369
If you have comments or questions regarding CNFAIC operations or winter recreation management, please email staff@chugachavalanche.org
© 2017 Chugach National Forest Avalanche Information Center. All rights reserved.
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