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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Sunday, December 18th 2016
Created: Dec 18th 5:34 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
Special Announcement

What are you doing Tuesday night?? Come to the Blue & Gold Boardshop for a CNFAIC presentation on the 'Turnagain Pass snowpack'!! This will be an interesting discussion considering the interesting snowpack! Details on link.

Motorized use:  The Chugach National Forest continues to monitor snow coverage daily for motorized openings. A 36” base is a general number the Forest uses to determine adequate coverage - this could be more or less depending on snowpack density. Thanks for your patience and don't let up your snow dance….


The Bottom Line

Strong winds along with several inches of new snow is expected to bump the avalanche danger to CONSIDERABLE. This will be in the Alpine elevations that see over 5" of snow accumulation. In these areas, fresh wind slabs up a foot thick may release naturally. Terrain that sees only 2-4" of snow, this could include the Turnagain Pass area, will remain at a MODERATE avalanche danger. Any slope over 30 degrees with recent wind deposited snow is suspect for triggering a newly formed wind slab avalanche. Watch for wind slabs along ridgelines as well as lower on the slopes due to cross-loading.

Safer (and likely more enjoyable) areas to recreate today will be in treed zones where the wind has not affected the snow. 

***Portage Valley ice climbers and hikers: A MODERATE danger exists below 1.000' where there is potential for avalanche debris, from a slide occurring above, to run through gullies. Avoiding gullies and runout zones is recommended.


Primary Concern

More blow than snow...? It looks like this may be the case for the storm that will be quickly moving through today. As of 6am this morning, Easterly ridgetop winds have jumped up and are averaging in the 30's mph. Snowfall has just begun in Girdwood and a trace has fallen on Turnagain Pass. If you are thinking of heading out today, expect quite windy conditions and increasing avalanche hazard. 

We are expecting anywhere from 2-6+" of new snow today. In favored areas, with over ~5" of new snow, we can expect the strong winds to form slabs quick enough that they release naturally. In areas with lower snow amounts, new wind slabs should be relatively shallow (6-10"). Slabs could also be a bit stubborn to trigger - keep this in mind as they could allow you to get out onto them before they release. Another thing, slabs may be thicker than expected if formed over Friday's wind slabs, adding to the consequences. Remember, expect any slab you find to be sitting on weak faceted snow and poor bonding is likely.

What to watch out for:

  • Areas with current wind loading (winds should blow all day)
  • Slabs lower on slopes from cross-loading
  • Stiff snow over softer snow (punchy snow)
  • Cracks shooting from your feet
  • Whumfing sounds (collapsing of the snowpack into the faceted snow underneath)

 

Photo: Wind effect on the Sunburst Ridge yesterday. In the back you can see the cross-loaded Northerly slopes on Magnum. (Thanks to Sam Galoob for sending us this picture and report)


Secondary Concern

Watch for fresh cornice growth. Small chunks of fresh pieces of cornice are likely to fall today. 


Mountain Weather

During the past 24 hours we have seen partly cloudy skies and no precipitation. Ridgetop winds were light yesterday and are ramping up this morning from an Easterly direction. Temperatures sit in the upper 20's F at the lower elevations up to treeline and have cooled slightly on the ridgelines to the upper teens. 

Today, we will be on the North edge of a large area of low pressure heading East. This will usher in strong wind and some snowfall. Easterly ridgetop winds are on the rise currently and should peak with averages around 30-40mph and gusts 70-80mph. Snowfall numbers are unfortunately meager with only 3-5" expected on Turnagain Pass, 1-2" in Summit Lake and 8-10" in the Portage Valley. The good news with the low staying so far South is temperatures should remain cool with a rain/snow line around sea level to 200'. Ridgetop temperatures will stay close the 20F with 1,000' temps in the upper 20's F.

An unsettled weather pattern will continue into the work week - it's difficult to tell what kind of snow amounts we will see - stay tuned tomorrow morning!

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 26  trace - 1" 0.1  23 
Summit Lake (1400') 21 
Alyeska Mid (1700') 28  0.5" 0.06  15 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 19   NE 15  56 
Seattle Ridge(2400') 22   SE  12  27 

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

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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