Avalanche Advisory

Turnagain Area Avalanche Advisory
Saturday, December 16th 2017 4:27 am by Heather Thamm
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche danger is CONSIDERABLE both at Treeline and in the Alpine where triggering a storm slab 1-2’ deep is likely on slopes steeper than 35 degrees. In the Alpine, above 2500’, triggering a much deeper and more dangerous avalanche, 4 - 6+ feet thick is possible today and could be unsurvivable. Obvious clues like whumpfing and recent avalanches may not be present. Cautious route-finding and conservative decision-making are essential. 

Below 1000’, where little snow exists, there is no danger rating. 

**Click HERE for the Summit Lake Summary

 Show the Complete North American Avalanche Danger Scale
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.
0 NO RATING Below Treeline / Below 1,000'
Special Announcement

Save the dates for two upcoming CNFAIC Fireside chats, December 19th at Blue & Gold Boardshop in Anchorage and December 21st at Powder Hound Ski Shop in Girdwood. Both will discuss lessons learned from past avalanche incidents.

Avalanche Problem 1

Yesterday strong Easterly winds combined with 13” of new snow have created storm slabs in the mid and upper elevations of Turnagain Pass. These newly formed slabs could vary in size from 1-2 feet thick and could be easy to trigger today. Due to strong winds yesterday these slabs may be wind loaded further downslope than expected and could catch you by surprise. Expect slabs to be thicker on leeward features  and along gullies where the snow has been cross loaded. Cornices are also likely to be tender. In the alpine triggering a storm slab or cornice could also wake up a much larger and more dangerous avalanche deeper in the snowpack. Don’t forget we have had continued stormy weather and elevated avalanche danger for the last two weeks including periods of heavy precipitation (both rain and snow), strong winds, and lots of recent avalanche activity. These are all red flags warning signs the snowpack needs more time to adjust to it’s new load. Maintaining a conservative mindset and avoiding slopes steeper than 35 degrees is recommended. 

Active wind loading was observed yesterday on Tincan early in the storm. 


Avalanche Problem 2

Above 2,500' very little information is known about the snowpack, but we do know that 5-8' feet of snow has fallen over the last two weeks and landed on weak faceted snow with crust(s) near the ground. Last week this set-up was very reactive and there were multiple remote triggered avalanches in Turnagain Pass. More time and information is needed to determine the sensitivity and distribution of the deep persistent slab problem. Likely trigger spots will be thinner area of the snowpack wear winds have stripped snow. Unless you have x-ray vision these thinner areas will be impossible to know. Finding a shallow spot could have devastating results. This type of avalanche would be unsurvivable. There may be no obvious clues to indicate instability and digging to find the weak layer could be challenging.  Conservative route-finding will be essential due to the potential for large avalanches.

A snow pit at 2250' yesterday found weak faceted snow near the ground to be reactive. This pit was intentially dug in a thinner area of the snowpack, a place where triggering a deep slab will be more likley. At this elevation (2250') several crusts are forming within the snowpack which is helping to strengthen the slab and make triggering at this lower elevation less likely. In the higher elevations where drier snow has fallen little is known about how the weak layer and slab are adusting. 

Mountain Weather

Yesterday a storm moved through our region dumping 13” of snow (1.0” H2O) at Turnagain Pass and similar amounts in Girdwood. Temperatures remained in the upper 30F’s at seal level and precip fell as rain to about 700’ until early this morning when temps cooled and about an inch of wet snow fell in the lower elevations. Strong Easterly ridge top winds averaged in the 20’s (mph) with some gusts reaching the 70’s mph. Winds decreased early this morning to 10-20mph.

Today expected scattered snow showers with up to 3” possible. Precip may be in the form of light rain up to 800’. Temperatures could reach the mid 30F’s at 1000’. Southeast ridgetop winds may be gusty this morning, but are expected to depreciate mid-morning to 5-15mph today.  

Tomorrow scattered snow showers are likely and winds are expected to be light to moderate from the East as a weak low moves over the Kenai Peninsula.  A window of clear weather is forecasted for Monday before another round of rain and snow moves through our region. At this point there is a lot of uncertainty as to what type and how much precipitation we will see next week.  

* Sunburst weather station is down due to loss of battery power.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 31  13  1.0  38 
Summit Lake (1400') 30  0.3  11 
Alyeska Mid (1700') 30  13  1.16  31 


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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') *n/a  *n/a    *n/a  *n/a  
Seattle Ridge(2400') 26  SE  20  76 

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, 2018 )

Glacier District
Johnson Pass: Open
Placer River: OpenPlease avoid private property and AKRR job site at Luebner Lake. Cross railroad tracks if needed, do not ride down tracks, it is illegal.
Skookum Drainage: OpenCross railroad tracks if needed, do not ride down tracks, it is illegal. FYI, Skookum drainage closes to Snowmachines on 4/1 as per the Chugach NF plan.
Turnagain Pass: Open
Twentymile: OpenCross railroad tracks at designated spot as you leave the parking area.
Seward District
Carter Lake: Open
Lost Lake Trail: Open
Primrose Trail: Open
Resurrection Pass Trail: OpenResurrection Pass trail is open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Open
South Fork Snow River Corridor: Open
Summit Lake: Open

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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.

If you have comments or questions regarding CNFAIC operations or winter recreation management, please email
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