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Avalanche Advisory

Turnagain Area Avalanche Advisory
Thursday, March 29th 2018 4:55 am by Aleph Johnston-Bloom
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche danger continues to be MODERATE above 1500’ on all aspects. Triggering a hard slab avalanche 2-4 feet thick remains a possibility and may be triggered remotely. Pay attention to afternoon warming and give cornices a wide berth. 

Similar avalanche concerns exist in the Summit Lake area  and other zones on the Kenai.

 


 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.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Avalanche Problem 1

Deep Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

With little change in the weather and the days since avalanche activity increasing, the chances of triggering an avalanche are decreasing. The core Turnagain terrain is trending towards LOW hazard. However, we are still concerned about someone triggering a hard slab avalanche 2-4’ deep, especially in periphery areas like Girdwood and the South end of the pass towards Johnson and Lynx. The weak layers in the snowpack that formed in January will not just go away but over time can become "dormant". The question is... are they? Without any big changes in the weather, these older layers (facets and buried surface hoar) are becoming more and more difficult to trigger and we are in a low probability, high consequence situation. The tricky part about this is, the pack appears to be stable but the chance remains for an unmanageable and destructive avalanche if a person hits just the wrong spot. No obvious signs of instability may be present before a slope releases and it may be the 10th skier or snowmachiner onto a slope that finds a trigger point. These trigger spots will be in thinner areas of the snowpack near rocks or in scoured areas along ridges. Although triggering a slab remotely is also becoming less likely with time, it is not out of the question with this snowpack structure. 

If the sun does shine today be aware of warming later in the day on Southerly slopes. 

Poor snowpack structure in Summit Lake. The concern is that the snowpack in the Southern end of the pass is very similar to this and a trigger spot may still be found.

 

It can be hard to remember that under all the hard wind affected snow and crusts there is a slab over buried weak layers. 

 


Additional Concern

Cornice

Many cornices are quite large. Temperatures have been cool lately but as we head into warmer, sunnier weather remember this can help de-stabilize them. As always, give cornices plenty of space and limit exposure underneath them.


Mountain Weather

Yesterday was partly to mostly cloudy in the morning becoming overcast in the afternoon. There were a few snow showers. Temperatures were in the mid 20Fs to mid 30Fs. Winds were light and variable. Overnight skies were mostly cloudy and temperatures were in the 20Fs and winds remained light.

Today will be mostly to partly cloudy with a chance of snow showers. Temperatures will be in the 20Fs to low 30Fs. Northwest winds will be light. Tonight will be mostly cloudy with a continued chance of snow showers, temperatures in the 20Fs and light winds.

Tommorrow clouds decrease and skies clear for the weekend. As high pressure sets up there is an increased chance of outflow winds impacting the area. Clear and sunny looks to be the pattern into next week. Time to do some spring snow dances! 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880')  29  0  0  76
Summit Lake (1400')  31  0  0  30
Alyeska Mid (1700')  30  0  0  72

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  22  variable  15
Seattle Ridge(2400')  27   variable 

 2  

 14

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: Dec 01, 2018 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed
Placer River: ClosedClosed
Skookum Drainage: ClosedClosed
Turnagain Pass: ClosedClosed November 21 due to inadequate snow conditions. #hopeforsnow
Twentymile: ClosedClosed
Seward District
Carter Lake: ClosedClosed
Lost Lake Trail: ClosedClosed
Primrose Trail: ClosedClosed
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: ClosedClosed
South Fork Snow River Corridor: ClosedClosed
Summit Lake: ClosedClosed

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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.


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
© 2018 Chugach National Forest Avalanche Information Center. All rights reserved.
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