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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Sunday, December 15th 2013
Created: Dec 15th 6:35 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.
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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Special Announcement

A reminder that all motorized areas on the CNF remain closed in order to prevent resource damage - snow depth is increasing but still insufficient.


The Bottom Line

With 2 days of new snow and wind, we have a MODERATE avalanche danger for wind slab and loose snow avalanches. Wind slabs 1-2+’ deep will be possible for a person to trigger on upper elevation slopes over 35 degrees. Watch for any area where the wind has blown the new snow into drifts and slabs – most likely just off ridgelines and rollovers. Otherwise, sluffing in the new light snow should be expected.

*Check out the storm totals below in the Mountain Weather section.


Primary Concern

Wind slab avalanches will be the most concerning avalanche problem today. With storm totals upwards of 15-18" these are expected to be 1-2+’ deep, soft and potentially quite sensitive to human triggers. They are most likely to be found on slopes over 35 degrees just off ridgelines, on rollovers and the side-walls of gullies. Keep an eye out for any slope with signs of recent wind loading - this means areas with stiffer snow over weaker snow, smooth rounded surfaces and hollow feeling snow.

Though the wind died down in most locations yesterday afternoon, it was blowing moderately to strong from the east early in the day yesterday. Though any natural activity has likely ceased, I’m expecting there are some good sized wind slabs that are still fresh enough to cause problems for people. If the visibility breaks enough for travel to the more exposed terrain, finding a 2’ deep unmanageable wind slab is not out of the question.


Below is a poor image of a few small wind slab avalanches on Tincan yesterday (human triggered 2,500', W aspect). It is still uncertain how the upper elevation wind affected slopes are handling this new load. More on yesterday HERE and HERE.


How is the early December crust behaving?
The new snow did fall on a ~¼” breakable crust which had, in places, surface hoar on top. Though this interface was showing a fairly good bond yesterday, I would not count out that avalanches could be larger and run further with this crust providing a slippery bed surface and the added uncertainty of the now buried surface hoar.


Secondary Concern

It will be mostly a sluff management day. With decreasing temperature and generally calm to light winds, much of the new snow will be in a very loose unconsolidated state ('cold smoke'?) and initiating a loose snow avalanche will be likely. In continuously steep, channeled terrain expect sluffs to gain in volume, run fairly far and become more of a concern.


Mountain Weather

24-hour snowfall totals (6am Saturday to 6am Sunday):

  • Turnagain Pass SNOTEL: 9” (0.5” water equivalent, 5.5% density-dang...)
  • Summit Creek SNOTEL: 3”  (0.2” water eq., 6.67%)
  • Girdwood Valley: ~6” (0.4” water eq., 6.7%) *not all Girdwood Valley stations reporting - rough estimate.

 Storm totals are (8am Friday to 6am Sunday – past 46 hours):

  • Turnagain Pass: 17”  (1” water equivalent, 5.9% density)
  • Summit Creek SNOTEL: 8”   (0.5 water eq., 6.25%)
  • Girdwood Valley: ~15”   (~1” water eq., 6.7%)

Currently, light snowfall continues in the Eastern Turnagain Arm which may add another inch this morning. The easterly wind that averaged 20-30mph with gusts to the 50’s yesterday morning has decreased to the 5-10mph range and backed to the north. Temperature has dropped from the 20's to the single digits overnight.

Today, skies should slowly break and snow showers taper off as the low pressure over us heads east and colder drier air moves in. Wind looks to remain light, 5mph, from the north and temperature remain in the single digits to low teens at most locations.

Tomorrow and Tuesday look to be clear and cold before another system moves in Wednesday/Thursday. It looks like winter is arriving!

 

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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