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Avalanche Advisory

Turnagain Area Avalanche Advisory
Monday, November 27th 2017 6:04 am by Wendy Wagner
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

AVALANCHE DANGER IS EXPECTED TO RISE THROUGH THE WEEK. Today is the first snowfall in a series of snow events - as snow begins to pile up in the coming days, natural and human triggered avalanches will become likely.  

A quick shot of snow overnight has hit Portage and Girdwood Valley with 4-6+ inches of snow and Turnagain Pass with 1-2 inches. Another 1-3 inches is expected through the day. This new snow combined with moderate Easterly winds will increase the avalanche hazard to MODERATE for areas seeing over 4 inches. Along ridgelines and sub-ridges, watch for places the winds have formed soft sensitive wind slabs. Getting pulled down by even a small slab could have a very rough ride due to rocks and thin snow cover. Small sluffs may be seen today as well in the Portage Valley and areas favored by the storm.

*ICE CLIMBERS in Portage Valley: Small avalanches today, and growing in size this week, could release naturally in higher terrain, sending debris over climbing routes. 

**For Hatcher Pass avalanche conditions see hpavalanche.org.


 Show the Complete North American Avalanche Danger Scale
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.
Avalanche Problem 1

Normally, an article warning Alaska drivers of winter weather road condtions would be business as usual, but for those of us looking to recreate at or around Turnagain Pass, an area that has seen cold and dry conditions for November, it means it is FINALLY snowing. Temperatures have warmed, winds have increased and snow is falling. The storm is coming from the East, hitting Portage Valley with several inches of snow at sea level overnight. Girdwood Valley has seen 4-6" of snow at the mid to upper elevations. Turnagain Pass looks to be un-favored with a mear 1-2" so far. 

Light snowfall should continue today with an evening total of 6-8" at the upper elevations in Girdwood Valley and 3-5" at Turnagain Pass. The Summit Lake area may squeeze an inch or two, but this system looks to be favoring Portage Valley and North.

  

AVALANCHE CONDITIONS:

The excitement is building and powder fever is setting in. Please remember, not only is it early season, with plenty of rocks and alders to get caught in, we are also expecting increasing avalanche danger as well. 

What to watch for:
1 - How much new snow has fallen? 
2 - Has the wind blown, or blowing?
3 - Are there fresh wind slabs that crack at your feet? Stiffer snow over weaker snow?

Today's equation is relatively simple. New snow + wind = wind slabs. If you find an area that has seen enough new snow for a wind slab, it is likely to be triggered easily on the steeper slopes (such as 35 degrees or steeper). Turnagain Pass is still VERY thin and may only see a couple inches of new snow - in this case avalanches are not expected. In the Portage and Girdwood Valleys, there looks to be enough snow to form shallow wind slabs.

As we head into this week, the main concern is weak faceted snow that will be covered up in the next few days. See Heather's video below. Other slopes are covered with hard crusts and hard wind drifts. The weak faceted snow is our greatest concern for future snow load as it will likely inhibit the new snow from bonding. More to come on this during the week.

 

 A look at the ridgeline conditions before snowfall:

 

 

 


Mountain Weather

Temperatures have warmed (relatively, to the 20's and 30F), winds have increased from the East (Moderately, to the 15-25 mph) and snow is falling. The storm is coming from the East, hitting Whittier and spilling over into the Portage Valley with several inches of snow at sea level overnight. Girdwood Valley has seen similar, yet with 4-6" of snow at the mid to upper elevations. Turnagain Pass weather stations are reporting a mear 1-2" so far. 

Light snowfall should continue through most of the day and begin to tapper off this afternoon/evening. A total of 6-8" is expected at the upper elevations in Girdwood Valley and 3-5" at Turnagain Pass. The Summit Lake area may squeeze an inch or two, but this system looks to be favoring Portage Valley and North.

After this system passes, another yet stronger low pressure moves in Monday night. And another one after that. Here are the National Weather Station 'icons' for the grid point over Turnagian pass:

 



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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 26  1"  0.1"  7" 
Summit Lake (1400') 15  7" 
Alyeska Mid (1700') 20  4.5"  0.3"  11" 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  19  11 52 
Seattle Ridge(2400') 22  Sensor Rimed  Sensor Rimed   Sensor Rimed  

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 22, 2018 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed as of April 20th
Placer River: ClosedClosed as of April 17th
Skookum Drainage: ClosedClosed as of April 1st.
Turnagain Pass: Open
Twentymile: ClosedClosed as of April 13th
Seward District
Carter Lake: Open
Lost Lake Trail: ClosedClosed as of April 13th
Primrose Trail: ClosedClosed as of April 13th
Resurrection Pass Trail: ClosedClosed as of April 20th
Snug Harbor: Open
South Fork Snow River Corridor: ClosedClosed as of April 13th
Summit Lake: ClosedClosed as of April 20th

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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