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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Tuesday, December 31st 2013
Created: Dec 31st 6:39 am
2 Moderate Alpine / Above 2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
1 Low Treeline / 1,000'-2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
 Show the Complete North American Avalanche Danger Scale
The Bottom Line

There remains a MODERATE avalanche danger for triggering either a slab avalanche 12-18” deep or a fresh wind slab ~6" deep. Areas most concerning are steep slopes (approaching 40 degrees and steeper) and all aspects near and above treeline. Below treeline the danger is LOW where the snow cover is mostly loose unconsolidated snow.

*Avalanche danger will rise tonight into tomorrow as a strong storm system is bringing in the New Year.


Primary Concern

The weak snow that is buried 12-18” deep in our snowpack remains our primary concern. The likelihood for triggering a slab avalanche that breaks in this older weak snow has been decreasing the last several days but the possibility does remain.

We have a small shot of snow expected today (1-3” forecast) with moderate to strong wind. Slopes where the wind is depositing snow will add stress to these buried weak layers and increase the likelihood of triggering one of these old slabs. However, the ‘real’ snow and wind event is expected overnight tonight through tomorrow where a foot or more of new snow will have the potential to overload the weak layers. We could see large and unmanageable avalanches 2-3+' deep by tomorrow if this storm does verify.

Below treeline the slab is losing its cohesion and the pack is unsupportable. Though there is some localized collapsing in the alders, triggering an avalanche is unlikely.


Secondary Concern

Easterly winds will start picking up through the day to the moderate range on the ridgelines with gale force winds expected for tonight. Though there is limited snow to transport at the moment, we do have 1-3” of snow forecast to fall before 6pm. Watch for wind drifts and shallow slabs to start forming through the day. These should be confined to above treeline slopes and exposed rollovers.


Mountain Weather

We have had a mild past 24-hours with temperatures in the mid 20’s F above sea level, light easterly winds at ridge tops and overcast skies.

Today a change is in store as a large area of low pressure heads our way from the South. We should see East winds pick up by the afternoon to the 30-40mph range on the ridgelines with 70-80mph by late tonight. Temperatures should be around 20F above treeline and near 32 at sea level. Snow accumulation of 1-3” is expected with a snow/rain mix at sea level.

By tomorrow evening we are looking a total snowfall of 12-16” (possibly more). The models are saying around 1.5” of water equivalent from this afternoon through Wednesday night. It does look like we could finally get a decent shot of snow.

Some December stats below:

We end 2013 with a SWE that is only 15% of average for December. We also made the podium with this December being the 3rd driest since 1983. Numbers below are from the Turnagain Pass SNOTEL Station (1880’).

Top 5 lowest December SWE from 1983 till 2013:

1st  1984 – 0.5”
2nd  2011 – 1.3”
3rd  2014 – 2.5” (plus whatever might fall before midnight tonight)
4th  1985 – 3.1”
5th  2009 – 4.2”

Average December SWE is 16.2”

Snow Depth:
Dec 31 2013, today, snow depth 22”
Average for past 10 years is 64” (Data only goes back to 2004)

*The above numbers were calculated with SNOTEL data from the NRCS.

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: Mar 15, 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: Open
Skookum Drainage: OpenSkookum drainage closes to motorized use on April 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: Open
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
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