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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Sunday, January 20th 2013
Created: Jan 20th 6:46 am
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
2 Moderate Treeline / 1,000'-2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
2 Moderate Below Treeline / Below 1,000' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
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The Bottom Line

With the expected addition of new snow and continued wind over our region today the avalanche danger should rise to CONSIDERABLE above treeline. Upper elevation slopes may see up to a foot or more of new snow by this afternoon which will bring the threat of wind slab and storm snow avalanches. Expect these to be easily triggered by a person on slopes 35 degrees and steeper and in the 1-2’ deep range. There also remains the possibility a deeper and much larger avalanche could be triggered by a failure in the weak snow near the ground. A MODERATE danger will be found below treeline and in areas receiving less than a foot of new snow.


Primary Concern

With a few inches of snow overnight, plus the addition of 4-8” at treeline today, the upper elevation slopes could see a total of a foot of new snow by this afternoon. There are two main things that will keep this new snow from bonding quickly: (1) The storm will be “upside-down” – due to a rise in temperature with snowfall. This creates a situation where more dense snow is deposited over less dense snow forming a slab/weak layer combo. And (2), there are several slopes that received enough wind over the past few days to create a hard wind crust/slab that will act as a bed surface for this upside-down storm to fall on. A few of these hard surfaces had a couple inches of weak snow on top that will also help to keep the new snow from bonding right away.

In addition to the Storm Snow concerns we also have Wind Slab avalanches. East winds have ramped up overnight and should continue to be in the moderate to strong range on the ridgelines. Even if snow totals do not amount to much there is still plenty of snow available for transport to form 1-2’ deep wind slabs. These will likely be soft and easy to trigger.

Watching for all the obvious signs of instability will be key today. These are:
Recent avalanches
Shooting cracks, whoomphing and collapsing in the new snow
Heavy snowfall
Wind loading

Below treeline we will likely see wet snow falling on a crust. Watch for any new snow in these areas to have a hard time sticking to the crust as there will be 2” of weak snow sandwiched in between. This weak snow is the few inches that fell on Wednesday which began to facet with the cold temperatures Thurs/Fri. We may not accumulate enough snow at these elevations for it to become a problem but something keep in mind.


Secondary Concern

With warmer temperatures, the addition of a foot or so of snow (~1” of water equivalent ) and strong wind there is the possibility of adding enough load on certain slopes to wake up a deep slab here or there. This storm does not look big enough to induce a deep slab avalanche cycle similar to last Sunday/Monday, but we can’t forget the possibility remains that one of these larger slides could occur. The 4-8” of well developed faceted snow near the ground from our early season is still weak enough and present in our start zones to warrant concern.


Mountain Weather

Cloudy skies gave way to light snowfall yesterday as a low pressure system is pushing a warm front over our region currently. We have seen around 3" of snow overnight on Turnagain Pass, 4" at Girdwood Valley mid elevations and 2-3" down at Summit Lake. Temperatures have warmed to the mid-upper 30’s at sea level, where there is currently rain/snow mix, and mid 20’s F on the ridgelines. Winds have increased from the east averaging 35mph overnight and gusting over 60mph on the peaks.

Today we can expect another 4-8” of snowfall with the rain/snow line creeping up to 800’. The rise in temperature should allow ridgetops to get as warm as the upper 20’s by this evening. The strong east winds look to slowly taper off and blow around 25-30mph with gusts near 50mph through the day.

Tomorrow we should see a break in the precipitation and wind with another shot for Tuesday.

 


Fitz will issue the next advisory tomorrow morning, January 21st.

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: May 16, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedThanks all for a safe and fun season on the Chugach NF! Stay tuned for the 2017/18 season. #playsafe #snowtosealevel
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail will be open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
Summit Lake: Closed

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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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