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Avalanche Advisory

Turnagain Area Avalanche Advisory
Saturday, February 9th 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 is MODERATETriggering a large slab avalanche 2-3’ thick remains possible on steep slopes above 2,000'. These slabs can be triggered remotely from ridgelines and be large enough to bury, injure or kill a person. Identify high consequence terrain and practice safe travel protocols. Give cornices a wide berth, limit travel under glide cracks and watch your sluff.

SUMMIT LAKE / JOHNSON PASS: Areas south of Turnagain Pass harbor a thinner, weaker snowpack with multiple weak layers present including the MLK buried surface hoar. Human triggered slab avalanches 1-3' thick remain possible. Choose terrain wisely.

LOST LAKE / SEWARD: Thursday we received a report of a human triggered avalanche where someone was caught, carried and injured on the Harding Icefield trail. This avalanche occurred last Saturday, February 2nd. Seward and Lost Lake received new snow and winds over the past weekend. This area has very little snowpack info and extra caution is advised. 


 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

Heading to Hatcher Pass? GET the forecast! Check out the Hatcher Pass Avalanche Center Saturday Advisory click HERE.


Avalanche Problem 1

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

The MLK buried surface hoar roughly 1-3' deep has been responsible for 13 human triggered avalanches over the past two weeks. The last one was three days ago on Eddies On that day snowpack tests were pointing toward a stabilizing weak layer and then the 2'-3' deep avalanche was triggered remotely from the ridge on a steep, unsupported slope. This avalanche illustrates that snow pit tests are unreliable for the current problem. Furthermore, no signs of instability have been seen in conjunction with several of the large human triggered avalanches on this layer. 

This is a tricky situation if wanting to get on slopes over 35 degrees and have a safe day. Several tracks may be on a slope before it avalanches and slabs have been often triggered remotely from ridgelines. There are also many slopes that could in fact be stable, but unfortunately this problem is still a guilty until proven innocent situation.

What to keep in mind today:
   1-  This weak layer is widespread in the region and seems to be particularly suspect between 2000'-2500' due to a melt-freeze crust associated with it. 
   2-  Use safe travel protocol. Expose only one person at a time (this includes paying attention to other groups in the area), watch partners, stop in safe zones and be rescue ready.
   3-  Consider the consequences of an avalanche. Will the debris pile up deeply in a terrain trap or strain a person over cliffs and rocky terrain? Slopes with a fanning runout, spreading the debris, are more favorable for a positive outcome in the event of an avalanche.

   4-  As always, one can simply stick to slopes under 35 degrees with nothing steeper above to avoid the issue. Steep, connected, unsupported slopes are the most suspect!

Eddies remote triggered avalanche, 2-6-19.

 The MLK buried surface hoar layer was easy to spot in a pit on Seattle Ridge, 2-7-19. 


Avalanche Problem 2

Cornice

CORNICES: Last weekend there was a large cornice fall triggered in upper Seattle Creek drainage. Cornices are looming large in some of the Alpine terrain. Give them an extra wide berth as they often break farther back than expected.

LOOSE SNOW AVALANCHES (dry and wet): Dry loose “sluffing” is possible in steep terrain. Daily warming and radiation from the sun could warm surface snow on steep Southerly aspects. Watch for roller balls and small wet-loose avalanches especially under rocky areas. 

Corniced ridge and loose snow avalanches on Magnum back towards Super Bowl, 2-8-19.

 


Additional Concern

Glide Avalanches

Glide cracks are moving and opening across the region again. The last glide crack to release into an avalanche was roughly a week ago in the Summit zone just north of Manitoba. Look out for glide cracks and limit exposure under them.

Glide cracks below PMS Bowl on Magnum, 2-8-19.

 


Mountain Weather

Yesterday: Skies were partly to mostly cloudy with high overcast clouds. Winds were light and westerly and temperatures were in the 20Fs. No precipitation. Overnight temperatures dropped a little and winds remained light. 

Today: Mostly cloudy skies and light winds. Temperatures will be in the 20Fs to low 30Fs. No precipitation forecast. Overnight easterly winds will bump up with gusts into the 20s.   

Tomorrow: Mostly cloudy skies and snow showers throughout the day as a trough moves in from the west. Temperatures will be in the 20Fs and winds will be easterly 10-20 mph with gusts into the 30s. Monday looks to have a period of clearing before the next chance of snow Tuesday. 

*The Seattle Ridge anemometer (wind sensor) was destroyed. We have a replacement on the way and it should be operational by mid February.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 30  58 
Summit Lake (1400')  20    0    0   25 
Alyeska Mid (1700')  29    0    51  

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  26  W  3 18 
Seattle Ridge(2400')  29  *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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