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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Monday, December 19th 2016
Created: Dec 19th 5:22 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.
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

Don't forget about tomorrow 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….

Outside of Advisory Area - Petersville region:
We received a report from the Dutch Hills area noting very unstable snow; several slab avalanches 2' thick remotely triggered by snowmachiners. If your are headed that way PLEASE see the report and photos HERE.


The Bottom Line

There is a CONSIDERABLE avalanche danger in the mountians surrounding Turnagain Pass, Girdwood Valley and Summit Lake on the Kenai. New snow and strong wind yesterday have loaded a very weak layer of faceted snow and human triggered avalanches are likely on all slopes above 1,000'.  Slab avalanches ranging from 10-20" could be triggered remotely from ridgelines or valley bottoms. Today's message is simple: it is a day to play it safe and keep slope angles below 30 degrees with nothing above you.

Conservative terrain management and expert level snowpack assessment will be necessary for any travel in avalanche terrain. 

***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. 


Primary Concern

An exciting day was had in the backcountry yesterday. Both for weather and avalanches. It was a 'rapid loading' event as heavy snowfall from 6am till 5pm loaded slopes with medium density snow. Human triggered avalanches were numerous, yet we have not heard of anyone being caught up in these. From what we know, these slides were in "small terrain" which equates to smaller and more manageable avalanches. See all the reports sent in last night HERE - a big thanks to these folks for writing in!!  

Yesterday's snowfall totals:
     Turnagain Pass:  6-8"
     Girdwood Valley:  5-7"
     Summit Lake:  4-10" 

The snowpack is showing its hand and it's not a good one. Weak faceted snow sits under a slab anywhere from 8-20+" thick. The slab is relatively soft and composed of yesterday's new as well as the 4-8" that fell during the end of last week. Strong winds have redistributed the snow above treeline and slabs will vary in depth and stiffness. Things to keep in mind today:

  1. You are likely to trigger an avalanche on steeper slopes
  2. You can trigger these from below or from the ridgeline
  3. Facets are notorious for wide propagating slabs and remote triggering
  4. Watch for obvious signs of instability (recent avalanches, cracking and collapsing)
  5. Quick hand pits and poking the snow with your pole (away from a used up-track) are good ways to monitor the slab and weak snow underneath
     

If skies clear enough for travel outside of the trees, another thing to keep in mind:

  • Small terrain = small avalanches = relatively manageable
  • Larger terrain = larger avalanches = unmanageable

 

Photo: Crown of easily triggered 8" slab avalanche that sympathetically triggered three more small slabs on the other side of the gully. If you look closely you can see one in the background. More on that in video below. This is the definition of a 'touchy' snowpack.

  

Photo: Soft slab avalanche into a terrain trap in the Tincan Trees (left side of photo). Small terrain - small avalanche. Thank you to Kakiko Ramos-Leon for the photo. 

 

Photo: Remote triggered shallow slab avalanche on a rollover in the Eddies area, Andy Moderow.

 


 

Hopefully by this point you are convinced that once the visibility improves, very conservative travel is warranted in the backcountry. If you get out, please send us your photos and information - we will be monitoring the pack daily but your reports are invaluable!


Additional Concern

Expect cornices to be sensitive and easy to break off. They also are likely to trigger a slab avalanche below. If you choose to walk a ridgeline today, give these a wide berth and be aware of people below you.


Mountain Weather

Yesterday was a bone fide storm day on Turnagain Pass. Heavy snowfall began in the morning and tapered off last night. See the snowfall and water numbers below. Ridgetop winds were strong, averaging in the 20's mph with gusts into the 60's. Temperatures were relatively warm; low 20'sF on ridgelines and 30F at 1,000' in the parking lots. 

Today we can expect partly clearing skies - to some degree - and a chance for localized instability showers. Another 1-2" of snow could fall where these 'showers' take place. Temperatures will be slightly warmer, near 32F at 1,000' and increase to the upper 20's along the ridgelines. Ridgetop winds will be light, 5-10mph from a Westerly direction.

For this week, most of the weather is getting pushed South and we should see a mix between clearing skies and localized snow showers.
 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 26  0.7   30 
Summit Lake (1400') 26  2 (manual report 4+") 0.2  10 
Alyeska Mid (1700') 28  4 0.4  20 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 21   NE 26 67 
Seattle Ridge(2400') 23  SE  18  42 

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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