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Avalanche Advisory

Turnagain Area Avalanche Advisory
Saturday, January 5th 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 remains MODERATE in the Alpine and Treeline zones. Triggering a slab avalanche 2-3’ thick is still possible due to a weak layer buried by the New Year's storm. Natural glide avalanches are also possible today, limit/avoid exposure under glide cracks. Cornices are large, don't forget to give them a wide berth as they may be teetering on the edge of falling.

SUMMIT LAKE / JOHNSON PASS / LYNX DRAINAGE: South of Turnagain Pass, keep in mind multiple buried weak layers exist and recent avalanche activity from the New Year's storm was significant. More potential for triggering a large slab avalanches exists in this zone. 


 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.
Special Announcement
  • Hatcher Pass:  HPAC's Saturday morning forecast is up! Check it out HERE if headed that way.

Avalanche Problem 1

Persistent Slabs

Almost Certain
Very Likely
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Unlikely

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Although clear skies and excellent surface snow will greet us for the weekend and into the work week, there is a hidden layer of buried surface hoar that could cause us some problems. If you've been following along, you'll know that the New Year's storm cycle buried a couple layers of surface hoar formed around Christmas; these layers now sit 2-3' below the surface. There has only been one human triggered avalanche (Jan 2nd) known to have released on one of the layers, which is good news, but more avalanches could be lurking. We are finding the layers in many of our snow pits, though not all of them, and typically only one of the layers. More often than not, they are not showing signs of reacting. Again, this is good news. All this said, it is still likely that isolated pockets exist where a human triggered slab avalanche, large enough to hurt us, will be possible to trigger. 

This is a tricky situation. If choosing to avoid the problem all together, stick to lower angle slopes. If headed for the steep terrain, consider the consequences if part or all of the slope does release. Watch our partners and expose one person at a time. No obvious signs on instability are likely to be present and in fact the pack could feel and look completely stable. 

      
                  

A fantastic snow surface makes it hard to remember that there is a 'thin gray line' a couple feet under us. Note the line in Trip Kinney's snow pit from Pete's North 2,800'. This layer wasn't reactive yesterday in his pit, but that doesn't mean some booby-traps aren't out there.  

 

South of Turnagain - Lynx Creek/Johnson Pass/Summit Lake zone:  Not only are we concerned that the Christmas buried surface hoar may cause problems in this area, there remains a poor snowpack structure in general. There are facet/crust combinations that exist in the bottom portion of the snowpack. The New Years storm is believed to have overloaded both the buried surface hoar as well as these deeper layers. Take a look at the photos from the avalanche activity throughout Summit Lake. If you're headed this way, the pack does become more complex - evaluate terrain exposure and the snowpack as you travel. Remember ‘whumpfing’ and recent avalanches are obvious clues of instability.

 

Natural avalanche that released at the end of the storm on New Year's Day on the west aspect between Wilson's North and Wilson's South. We are suspect that this avalanche failed on buried surface hoar. 


Avalanche Problem 2

Glide Avalanches

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Glide avalanches are expected to release over the weekend. Believe it or not, these cold snaps have been known to trigger releases. Several glide cracks have avalanched over the last few days. Glide cracks have been seen in popular ski and snowmachine terrain and some are covered by new snow from the New Years storm. The best way to manage the problem is to avoid traveling under glide cracks. As a reminder, glide avalanches have occurred on Lipps,  Seattle RidgePenguin Ridge,  Lynx Creek and Johnson Pass this week.  

 

Recent glide crack that released in the northern portion of the Bench peak massif. This area is just southeast of Johnson Pass and seen from the Seward Highway.


Mountain Weather

Yesterday:  Mostly clear skies with some valley fog covered the region. Ridgetop winds were light from a NW direction (5-10mph). Temperatures were cold and inverted; single digits in the parking lots and the teens F along ridgelines.

Today:  Mostly clear skies and patchy valley fog will be over the area again today. Ridgetop winds are expected to remain light, 5-10mph, from the NW. Temperatures are cold (-5 to 5F) at the lower elevations and in valley bottoms as an inversion remains. Ridgeline temperatures are in the mid-teens with the warmest weather station being at the top of Max's Mt above Alyeska at 18F. 

Tomorrow:  Sunny skies and cold temps are on tap to remain for Sunday and into the week. The good news is, ridgetop winds at this point look to remain light from a NW direction. Models are hinting at the next chance for a precip event next 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') 10  60 
Summit Lake (1400') -2  20 
Alyeska Mid (1700') 11  47 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 14   W 5 14 
Seattle Ridge(2400') 13  *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: May 06, 2019 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed as of 4.3.19
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: ClosedClosed as of 5/6. Thanks for a great season all, see you next winter!
Twentymile: ClosedClosed as of 3.20.19 due to lack of snow.
Seward District
Carter Lake: Closed
Lost Lake Trail: ClosedClosed as of 3.22.19 due to lack of snow
Primrose Trail: ClosedClosed as of 4.3.19 due to lack of snow
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: ClosedClose as of 5.1.2019
South Fork Snow River Corridor: ClosedClosed as of 3.20.19 due to lack of snow.
Summit Lake: Closed

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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
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