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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Friday, January 13th 2017
Created: Jan 13th 6:13 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.
 Show the Complete North American Avalanche Danger Scale
The Libby Group
Special Announcement

Join us tomorrow, Saturday, at Hatcher Pass from 11am-1pm for a FREE rescue workshop!! This event to brought to you by Hatcher Pass Avalanche Center, the CNFAIC and the Alaska Avalanche School. More info HERE


The Bottom Line

The avalanche danger is expected to rise to CONSIDERABLE by the end of the day on upper elevation slopes receiving over 8" of new snow accompanied by strong wind. In this case, wind slabs 10-16" thick are likely to be triggered by people on leeward slopes and may release naturally. In areas unaffected by winds and receiving less snow (4-6" ish) the danger will be MODERATE where small shallow storm slabs and sluffs in the new snow may be triggered on the steeper slopes. 

*Today's avalanche danger is dependent upon how much snow this storm produces.

Ice climbers and hikers:  In Portage Valley and other areas where climbing routes and trails sit under avalanche paths, be aware that debris from a naturally occurring slide above may run to these lower elevations.


Primary Concern

It's official - after a two-week dry spell, snow is falling this morning!! Although there's only been around an inch so far, by this evening we could get up to 8-10" in favored locations and 4-6" in un-favored locations. Plus, an additional 4-6" is possible overnight tonight. It will be one of those days to keep close tabs on how much new snow has fallen and how hard is it snowing. This will directly influence the avalanche hazard. The new snow is falling on a variety of old surfaces, including slick hard wind slabs/crust and soft faceted snow. Despite the myriad of different surfaces, expect bonding of the new snow to initially be poor.

Upper-elevation slopes in the Alpine are likely to be obscured today, but this is the terrain most suspect for receiving enough snow (up to 8+") along with winds strong enough to form wind slabs that release naturally. If you find yourself in this situation, expert level snowpack assessment is necessary for entering avalanche terrain. Mid-elevation slopes and areas in the trees are more likely to receive less snow (4-6") and little wind. In this terrain, naturally occurring avalanches are unlikely but human triggered shallow soft slabs and sluffs, the depth of the new snow, may be possible on the steeper slopes. 

What to watch for:

  1. How much new snow are you traveling through?
  2. Heavy snowfall, strong winds?
  3. Cracking in the new snow?
  4. Are you traveling under an avalanche path that may be loading with snow above you?

Stepping off the skin track or jumping off your snowmachine to do quick hand pits will be a great tool for sussing out new snow depth and bonding. If skies are clear enough, look for loose snow avalanches in the steep terrain and keep your situational awareness up as the day progresses! 

Photo below: An example of the pre-existing snow surface that the new snow is falling on - old hard wind slabs/crusts. Very weak faceted snow sits under these hard slabs and crusts. Once the storm snow bonds with the crust we could see avalanches breaking in the faceted snow beneath (will we get enough of a load for this? a focused question for this weekend).
 


Additional Concern

Warming temperatures associated with the Southerly flow may enhance glide activity. Glide cracks have been slowing opening this week; though we have not seen/heard of any new cracks releasing. Keep an eye out for cracks, which is difficult with new snow and wind, and limit time underneath them.


Mountain Weather

Yesterday was our last clear sky day with temperatures in the single digits in valley bottoms and the teens-20's in the upper elevations. Ridgetop winds picked up later in the day from the Southeast to the 10mph range.

Overnight, clouds filled in and light snowfall began around 3-4am. Roughly a trace to an inch is being reported at stations this morning, including snow to sea level. Ridgetop winds have bumped up to 15-20mph with gusts into the 30's. Temperatures have climbed dramatically at sea level as the inversion has been scoured away (28-30F at sea level, mid-20's at the mid-elevations and mid-teens at the Ridgetops).

Today, we are expecting anywhere from 4-8+" of new snow and another 4-6" tonight. Although temperatures have warmed dramatically, we should still see mostly snow to sea level with this event. Ridgetop temperatures will be in the mid-20's F. Ridgetop winds are likely to increase more today into the 20-40mph range with gusts into the 50's.

Tomorrow the system looks to move out and skies begin to break up as a cold and dryer North flow heads our way.

 

PRECIPITATION 24-hour data (6am - 6am)

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 21  trace  33 
Summit Lake (1400') 10  11 
Alyeska Mid (1700') 20  0.3  0.1  21 

 

RIDGETOP 24-hour data (6am - 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  16 30 
Seattle Ridge(2400')  17  SE  17  35 

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 28, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: ClosedSKOOKUM DRAINAGE CLOSED TO MOTORIZED USE ON APRIL 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: OpenOpen thru May 14th.
Twentymile: Closed
Seward District
Carter Lake: OpenClosed May 1.
Lost Lake Trail: OpenClosed May 1.
Primrose Trail: OpenClosed May 1.
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: OpenClosed May 1.
South Fork Snow River Corridor: OpenClosed May 1.
Summit Lake: OpenClosed May 1.

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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