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Avalanche Advisory

Turnagain Area Avalanche Advisory
Monday, January 7th 2019 7:00 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 remains MODERATE above 1,000'. Triggering a slab avalanche 2-3’ thick is still possible. Wind affected terrain in the Alpine is the most suspect. Glide cracks are opening and have been avalanching during this cold snap. This is the time to avoid being under cracks. As always, give cornices a wide berth and watch your sluff. 

SUMMIT LAKE / JOHNSON PASS / LYNX DRAINAGE: South of Turnagain Pass, keep in mind multiple buried weak layers exist in the middle and base of the snowpack. More potential for triggering a slab avalanche 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

There have been three avalanche fatalities in the US this season. Two occurred on Saturday, January 5th. Our thoughts go out to the family, friends and all impacted by these accidents. 


Avalanche Problem 1

Persistent Slabs

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A buried layer of surface hoar may sit 2-3' below the surface of the snow. Zones that saw prior wind effect (especially in the Alpine) are most concerning where the buried surface hoar is potentially sandwiched between layers of harder snow. This was the set-up in the one known human triggered avalanche on this layer that occurred on Wednesday, Jan. 2nd on Seattle Ridge. As time passes, high pressure and cold temperatures continue and more information is gathered, we are finding that being able to trigger a slab avalanche breaking 2-3' deep is becoming less and less likely. Most snowpack tests and pits have shown the layer to be either generally unreactive or not present. The spooky part is that it has been found in a few pockets with the hard snow above and below and the potential to initiate an avalanche. Signs of instability will likely not be present. 

When there is a buried surface hoar in the snowpack it is always important to consider the consequences if part or all of the slope does release. Is there a terrain trap below? Remember to use safe travel protocols: watch your partners, expose one person at a time and have an escape route planned. 

Buried surface hoar sandwiched between hard layers of snow. 1-2-19.  

South of Turnagain - Lynx Creek/Johnson Pass/Summit Lake zone:  A poor snowpack structure exists in these areas. The buried surface hoar mentioned above exists as well as facet/crust combinations in the bottom of the snowpack. The New Year's storm overloaded a variety of these weak layers as can be seen in photos from the avalanche activity throughout Summit LakeIf you're headed this way, the snowpack becomes more complex - evaluate terrain exposure and the snowpack as you travel. 


Avalanche Problem 2

Glide Avalanches

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Glides cracks have been observed in all the hot spots on Turnagain: Seattle Ridge, Lipps, Tincan, Eddies, Lynx Creek, Johnson Pass, Sunburst, Corn Biscuit and Magnum. "Gliding" is the whole snowpack is slowly sliding down the mountainsides and can release into an avalanche at anytime. This is a completely unpredictable situation and one where a human does not play a role. Glide cracks have been releasing into large avalanches over the past week. Please don't be caught in the wrong place at the wrong time and limit/avoid exposure under any crack you see. The most recent glide avalanche we know of was on the south face of Eddies where the glide debris covered fresh ski tracks. Cracks maybe white and look like bergshrunds at first before progressing to the brown frown and the snow sometimes looks like a wrinkled sheet on the slope below. Glide cracks have now been observed in both the Alpine and Treeline elevation bands. 

Glide cracks in the Library, 1-6-19. Photo: Andy Moderow

 Glide cracks in Petersen Creek, 1-6-19. Photo: Alan Abel


Mountain Weather

Yesterday: The pattern of cold temperatures, clear skies and valley fog continued yesterday. Highs were in the low teens to single digits and lows were below zero with a slight inversion. 

Today: Another cold, clear day with valley fog is forecast. Highs will be in the teens at upper elevations and lows will be in the single digits. Winds will be light and southerly. Temperatures will slowly rise with a chance of light precipitation overnight. 

Tomorrow: Partly to mostly cloudy skies and a chance of snow showers with temperatures in the high teens. On Wednesday the pattern goes back to clear, sunny. Warmer temperatures and snow are in the long-term forecast for 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')  0   0 57 
Summit Lake (1400') -7    0   20  
Alyeska Mid (1700') 3  0 46 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') NW  17 
Seattle Ridge(2400')  3   *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
If you have comments or questions regarding CNFAIC operations or winter recreation management, please email staff@chugachavalanche.org
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