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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   John Fitzgerald  
Monday, January 20th 2014
Created: Jan 20th 5:56 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.
 Show the Complete North American Avalanche Danger Scale
The Bottom Line

The avalanche hazard is CONSIDERABLE above and below treeline today.

Below treeline wet loose avalanches have the potential to move in steep terrain.

Above treeline, fresh wind slabs up to 3 feet in depth will be sensitive to the weight of a person or snowmachine.  These slabs have the potential to pull out deeper weak layers in the snowpack.  The possibility of triggering full depth slab avalanches up to 5 feet deep warrant very conservative terrain choices today.

Avoidance of terrain over 35 degrees, wind loaded starting zones, and thin spots in the snowpack is the best way to navigate around the following concerns:


Primary Concern

Winds over the last day have blown enough to transport snow and create new slabs 2-3’ in depth in the higher elevations.  Winds today out of the East will continue to build slab depths on leeward slopes.  We currently have very limited information from the upper elevations.  If venturing into the higher elevations today, treat wind loaded areas with a healthy dose of suspicion.  Wind slabs that have formed over the past day and continue to build today have the potential to slide easily.  This problem on its own is enough to bury a person.  Add into the mix the chance of triggering a deep slab and the end result could be grim.

It is important to know how to recognize snow that has been wind loaded.  Smooth, rounded and pillowy are a few ways to describe the look of wind slabs.  Snow will feel more stiff in wind loaded areas.  Shooting cracks are an obvious sign of a wind slab that is unstable.


Secondary Concern

This past weekend brought much needed precipitation to the area.  Rain fell up to 2,500’ but changed over to snow by Friday afternoon.  The upper elevation starting zones have received well over 2’ of snow in the past 3 days.  At the bottom of the snowpack, up to 5’ down in some locations, is weak snow.  In many places it will be difficult to impact that weak snow that is far below you.  However, snow does not sit uniformly across the mountains.  Snow depths will vary from 1-5 feet in the upper elevations.  It is in these spots with thin snow coverage that need to be avoided.  The likelihood of triggering a deep, unsurvivable slab will go up if people hit thin spots.  The obvious signs of unstable snow will not necessarily be present.  Snowpit tests may or may not always point to this problem.  In order to understand this problem it is crucial to know the history of the season up to this point.  History tells us that the foundation is weak and not trustworthy.

This video shows the problem.  It takes a lot of force to trigger a slab in this test.  Once it does fail the entire snowpack (column in this case) slides.

 


Additional Concern

Warm temperatures and rain have done a number on the snowpack at the lower elevations.  Warm temperatures in the lower elevations will persist throughout the day.  While the chances of wet slabs releasing have gone down over time, the threat of dangerous wet loose avalanches is something to be aware of.  Avoid steep terrain in the lower elevations today.  If your snowmachine, skis or board is punching through the entire snowpack, it is definitely time to back off of steep terrain.  Pay attention to what is below as well.  Terrain traps such as trees, cliffbands and gullies will amplify the consequences of being caught in a wet loose avalanche today.


Mountain Weather

In the past 24 hrs the mountains around Eastern Turnagain Arm have received 6” of new snow with .6” of water equivalent.  Ridge top winds have been out of the East averaging 36 mph with gust to 86 mph.  Temperatures have continued to remain mild, with freezing level up to 2,000’ overnight.  The Sunburst station at 3,812' has averaged 22 deg F.

Today expect light snow/rain and mild temperatures.  Winds will be out of the East at 40 to 50 mph.  Snowfall in the upper elevations will accumulate up to 3” with rain/snow line around 1,300 feet above sea level.  Temperatures at 1,000’ will be in the high 30s F.

We will remain under the influence of an active weather pattern and a general Southerly flow over the next several days.  Expect temperatures to remain mild and precipitation to be on and off through the week.

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

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
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