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Avalanche Advisory

Turnagain Area Avalanche Advisory
Wednesday, January 17th 2018 4:33 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 is HIGH today at all elevations.  Heavy rain, snow and strong winds have created very dangerous avalanche conditions. Natural avalanches are likely and human triggered avalanches are very likely.  Avalanches may be very large and run long distances. Travel in the mountains is not recommended. Avoid all runout zones. 


 Show the Complete North American Avalanche Danger Scale
4 High Alpine / Above 2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4 High Treeline / 1,000'-2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4 High Below Treeline / Below 1,000' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
Avalanche Problem 1

Wet Slab

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

The region has received 2" of rain in the past 24 hrs. The rain fell at least as high as 3000'. Another half an inch of rain is forecasted to fall today up to 2400'. As the water moves into the snowpack it break bonds, adds load and can lubricate weak layers and/or run along crusts, causing large wet slab avalanches. We know we have existing weak layers and crusts buried in the snowpack. Rain may also initiate large wet loose avalanches that could trigger the wet slabs. It is best to visualize the snowpack that has been affected by rain has now turned into a giant, scary slurpee that is out to get you. Avalanches were observed in many paths on Seattle Ridge yesterday and in channeled terrain along the Seward highway. Some of these avalanches were running to the valley bottom. This is very good reason to avoid travel in runout zones. Travel in the mountains is not recommended today. 

Debris in an avalanche path off of Seattle Ridge. 

Fresh debris overrunning old debris in one of the Petersen slide paths. 

                                                         Slurpee Monster 

 


Avalanche Problem 2

Storm Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

At higher elevations the precipitation is falling as snow and there were strong winds in the last 24 hrs.  Large storm slabs may have developed in the Alpine depending on how well the new snow bonded to the layer below. Leeward slopes may be very loaded and cornices may be large and tender today. 


Additional Concern

Deep Persistent Slabs

The additional load, either from rain or snow combined with high winds, will be stressing the persistent weak layers of snow we know exist in the snowpack. We have two layers of buried surface hoar, a variety of facet/crust combinations and weak faceted at the ground. Avalanches initiating in the upper snowpack may step down to these layers and cause large, deep, dangerous avalanches. 

Snowpack near the skier triggered avalanche that occured on Eddies Monday. Click HERE for full observation.

Eddies avalanche from below. 

 


Mountain Weather

Yesterday skies were obscured and rain fell throughout the day. Rain/snowline was observed as high as 3000' and may have gone higher. Around 2" of rain fell across the region. Temperatures were in the 40Fs at sea level and 30Fs to high 20Fs at ridgetops. Winds were easterly 20-30 mph gusting as high as 70 mph on Sunburst. 

Today should see cloudy skies and continued rain and snow during the day tapering off in the evening. Rain/snowline is forecasted to be around 2400'. Temperatures will cool down this evening with lows in the 20Fs tonight. Winds will be easterly 25-35 mph with gusts into the 40s today and be light overnight.

Tomorrow looks to be clear and sunny with temperatures in the 20Fs and light westerly winds. Cooler temperatures and partly cloudy skies are forecasted for the weekend. 

 *Alyeska Mid stopped recording data at 6pm last night. Alyeska top of quad (2800') weather station received 1.9" of water in the last 24 hrs. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 33   1 2 57 
Summit Lake (1400') 34    0  .4   15
Alyeska Mid (1700')  *34  *0 *1.4  *45 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 27  ENE 27  70 
Seattle Ridge(2400')  31  SE 25  63

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: May 06, 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: ClosedClosed as of May 7th. Happy summer, see ya when the snow flies!
Twentymile: ClosedClosed as of April 13th
Seward District
Carter Lake: ClosedClosed as of 4/27
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: ClosedClosed as of 4/27
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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