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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Sunday, December 9th 2012
Created: Dec 9th 6:53 am
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
3 Considerable Treeline / 1,000'-2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
3 Considerable Below Treeline / Below 1,000' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
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The Bottom Line

There is a CONSIDERABLE avalanche danger today for storm and wind slab avalanches, both above and below treeline. Recent new snow and strong wind has created an extremely unstable snowpack and dangerous avalanche conditions exist. Very weak faceted snow sits under the new storm snow and wind slabs making it difficult for any new accumulation to stick to the mountain sides. Human triggered slab avalanches are LIKELY today on slopes steeper than 30 degrees above and below treeline. The wind, snow and natural avalanche activity has abated but the snowpack remains teetering on the edge of release. If you are not certain where avalanche terrain exists, in order to avoid it, travel in the backcountry is not recommended.


Primary Concern

High winds yesterday afternoon through midnight, sustained around 40mph with gusts over 70mph, raked the mountains, scouring windward slopes and depositing a combination of new snow and existing snow onto leeward slopes and catchment zones. Even the mid and lower elevation snow saw substantial wind transport. There was likely a peak in natural wind slab acivity and HIGH danger at the tail end of these strong winds overnight.

Wind slabs that were just starting to be formed yesterday were 4-10” thick, very sensitive and could be cracked out and released with the slightest touch. Because these slabs have formed on very weak sugary snow they are not likely to bond anytime soon.

Steering clear of ANY wind deposited snow on slopes over 30 degrees will be prudent. These areas may not be obvious as 1-3” of new snow forecast with little wind today could mask these monsters. Remotely triggering a slope (i.e., from below or a flat area) is possible. Collapsing and cracking should be widespread - if you are on a slope steep enough it will probably avalanche.


Secondary Concern

Though the forecast for 2 feet of snow by this morning was a bust and yesterday evening’s quick and dirty onslaught was finished around midnight, the 8-12” of new dense snow above treeline is highly unstable. Not only did the storm come in cold and leave warm (creating an unstable upside down storm layer), it fell on extremely weak faceted snow - ball bearings – that will have little chance of allowing the new snow to stick to the sides of the mountains. Hence, areas lacking a wind slab will still be likely to avalanche with just the new layer of storm snow.


Mountain Weather

Snowfall numbers (storm total as of 6am 12/9):
Turnagain Pass SNOTEL 1880’:  9” snow,  .7” water
Summit Lake SNOTEL 1400’:  3” snow,  .3” water
Alyeska mid mtn:  10” snow,  .8” water  (1.2” water at 2800’)

The leading edge of the first "real" storm system for over a month moved through quickly yesterday evening with strong easterly winds (sustained 40mph, gusting 70’s) and heavy snowfall in Eastern Turnagain Arm. As the storm weakens today there is a chance for another 1-3” as well as a few more inches for Monday. The easterly winds have decreased substantially since midnight and should be in the 10-20mph range on the ridgetops today. Temperatures around treeline increased from ~20F yesterday to the upper 20’s today where they should remain. There is a light rain/snow mix this morning at sea level along Turnagain arm with slippery roads.

 


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). 

Kevin will issue the next advisory Monday morning, December 10th.

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: Apr 11, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: OpenPlease park on road in and leave the turnaround (near outhouse) open for trailers to turn around.
Placer River: OpenWide swaths of open river in the Placer Valley. Travel with extreme caution!
Skookum Drainage: ClosedSKOOKUM DRAINAGE CLOSED TO MOTORIZED USE ON APRIL 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: ClosedClosed for the remainder of the 2017 season.
Seward District
Carter Lake: Open
Lost Lake Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Primrose Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Resurrection Pass Trail: ClosedClosed for 2016/17 winter season. This is a non-motorized season. This alternates every other year and will open again during the 2017/18 winter.
Snug Harbor: Open
South Fork Snow River Corridor: Open
Summit Lake: Open

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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
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