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Avalanche Advisory

Turnagain Area Avalanche Advisory
Wednesday, January 16th 2019 7:00 am by Wendy Wagner
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche danger is MODERATE above 2,000'. Old wind slabs 1-2' thick, along with shallow fresh wind slabs less than a foot thick, will be possible to trigger on wind-loaded slopes. In addition, glide cracks may release into avalanches; limit/avoid exposure under them. Give cornices a wide berth.

SUMMIT LAKE / JOHNSON PASS: Keep in mind buried weak layers exist in the middle and base of the snowpack. More potential for triggering a large slab avalanche exists in this zone, especially in terrain that was recently wind-loaded. 


 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.
1 Low Treeline / 1,000'-2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Special Announcement
  • Head down to Alaska Mountaineering and Hiking this evening for a discussion on the State of the Snowpack! Presentation by CNFAIC, from 7-8pm, more details HERE!

Avalanche Problem 1

Wind Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Wind slabs and cornices will be the main concern today as warm temperatures and a quick moving system rolls through. Ridgetop winds bumped up into the 'strong' category overnight from the east. With only a few inches of new snow accompanying the wind, fresh slabs should be shallow and less than a foot thick. Between 1-4" of snow fell last night at the upper elevations and another 1-3" is expected today. There is little old loose snow available for transport due to the strong winds last weekend, hence new slabs should be mainly composed of the new snow. Rain falling up to 1,800' will limit slab development in the mid-elevations. 

Evaluating surface conditions will be key if venturing into the backcountry. Look for loading patterns, i.e. is the slope cross-loaded or top-loaded? Watch for shooting cracks and listen for hollow sounds. These are signs of hard snow over softer snow and indicate wind slab potential. Wind slabs could be stiff enough to allow a person onto them before releasing. Old slabs could still be reactive as they may be sitting on weak snow underneath (near surface facets and surface hoar). 

Cornices:  The warming temperatures at the upper elevations can help destabilize cornices. Not only can they break farther back than expected, they may be more tender today and could also trigger a slab avalanche on the slope below. 

Old natural wind slabs on Raggedtop in the Girdwood Valley. Triggered by cornice falls likely last Sunday, 1/13. 

 


Avalanche Problem 2

Persistent Slabs

South of Turnagain - Johnson Pass/Summit Lake zone: A poor snowpack structure exists in these areas and strong winds over the weekend loaded leeward slopes. Multiple mid-pack weak layers of facets and buried surface hoar have been found as well as concerning facet/crust combinations in the bottom of the snowpack. If you're headed this way, evaluate terrain exposure and the snowpack as you travel. Be on the lookout for signs of instability and be suspicious of any wind loaded slope.


Additional Concern

Glide Avalanches

Many glide cracks are covered with recent snow/wind and may be hard to spot. Remember the known areas with cracks are Eddies, Tincan, Sunburst, Magnum, Cornbiscuit, Lipps, Seattle Ridge, Johnson Pass, Lynx Creek, Summit Lake, Petersen Creek, and Girdwood. Avoiding/limiting time under these features is prudent as they can release into an avalanche at any time and are completely unpredictable.


Mountain Weather

Yesterday:  Mostly clear skies were over the region with clouds and light snow/rain moving in overnight. Between 1-2" of snow has been seen at the mid-elevations. The rain/snow line is hovering between 1,500 - 1,800'. Ridgetop winds increased overnight and are blowing in the 30'smph this morning with gusts near 50mph from the east. Temperatures are warm, upper 20's to 30F along ridgelines, upper 30's at 1,000' and 40F at sea level. 

Today:  Mostly cloudy skies with light rain/snow showers are expected. Only 1-2" of new snow should fall in favored zones with light rain below 1,500'. Ridgetop winds are expected to stay strong, 20-30mph with gusts to 50mph from the east. Temperatures should also stay warm with ridgelines reaching 30F and sea level 40F. 

Tomorrow:  Clearing skies and decreasing winds are on tap as the system over the area today moves out. Mostly sunny skies are expected to last through Friday and possibly into the weekend.

*Seattle Ridge weather station was heavily rimed and the anemometer (wind sensor) was destroyed. We are currently working to replace it.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 33   0.2 53
Summit Lake (1400') 29  0.1  21 
Alyeska Mid (1700') 32  0.5  0.2  50 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 27 ENE  19  49 
Seattle Ridge(2400') 30  *N/A  *N/A   *N/A  

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 22, 2019 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Open
Placer River: ClosedClosed as of 3.20.19 due to lack of snow.
Skookum Drainage: ClosedPlacer access closed as of 3.20.19 due to lack of snow.
Turnagain Pass: Open
Twentymile: ClosedClosed as of 3.20.19 due to lack of snow.
Seward District
Carter Lake: Open
Lost Lake Trail: ClosedClosed as of 3/22. Unfortunately HEAVY rain over the past week has washed much of the snow off the lower stretches of this trail.
Primrose Trail: OpenPlease stay on trail to avoid resource damage through forested areas.
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: Open
South Fork Snow River Corridor: ClosedClosed as of 3.20.19 due to lack of snow.
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.


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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