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Avalanche Advisory

Turnagain Area Avalanche Advisory
Saturday, February 23rd 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

There is a MODERATE avalanche danger on slopes above 1,000'. Triggering a wind slab avalanche around a foot thick is possible on wind loaded steeper slopes. Additionally, sunshine and warm temperatures may cause wet sluffs in steep southerly facing terrain. As always, give cornices a wide berth and limit exposure under glide cracks.

GIRDWOOD / PORTAGE / PLACER:  Wind slabs could be deeper, up to 2' thick, due to more snow that fell last week. 

SUMMIT LAKE / JOHNSON PASS:  A shallow snowpack with various weak layers exist. Triggering a larger, more dangerous slab remains a concern. Conservative terrain choices and a cautious mindset is advised.

SEWARD / LOST LAKE:  Recent snowfall and strong northwest winds impacted this region as well. Watch for and be suspect of wind loaded slopes. Triggering a deeper more dangerous avalanche is uncertain due to limited snowpack information.


 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!
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Avalanche Problem 1

Wind Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

With a sunny and springlike weekend upon us, triggering a lingering wind slab is our main concern. Last Thursday's impressive outflow event loaded predominantly south and easterly aspects as the northwest winds hammered the mountains. We can expect wind slabs to be generally hard, stubborn and around a foot thick. The problem is that some slabs are sitting on weak faceted older snow, which is keeping them from bonding quickly. Furthermore, warming over the next several days can do funny things in the snowpack and cause slabs to be more touchy.

All this said, keep a close eye out for recent avalanches, whumpfing and cracking in the snow. Many slopes have variable wind effect with loaded areas and scoured areas. Watch for rounded and pillow like features as these are the windloaded areas that could slide. 

SUN EFFECT:  The days are longer and the sun is higher. Although the snow surface has seen a good degree of wind damage, southerly facing slopes may be soft and susceptible enough to product wet sluffs. There are three things acting in sync over the next several days to cause warming, 1) direct sun, 2) calm winds and 3) warm ambient temperatures. Watch for the snow to start to become moist or wet and remember even a small moist of wet sluff in steep rocky terrain can become unmanageable. 

 

Snow pit from Seattle Ridge's slide path Repeat Offender that sits just to the south of the motorized up-track.

 

 

Video is from Thursday (outflow event day) in the Skookum drainage. Video linked HERE


Avalanche Problem 2

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

South of Turnagain Pass in the Summit Lake and Johnson Pass area, a thinner and weaker snowpack exists. Various weak layers of facets and buried surface hoar reside in the middle and base of the pack. The strong NW winds Thursday proved these buried weak layers are still a concern as many natural avalanches were seen and many of these stepped down into the deeper weak layers. Moving forward, it's good to be very suspect of these regions with a thin snowpack. Avoiding wind loaded steep slopes and large terrain is prudent as not only a wind slab, but a larger slab may be triggered.

As a reminder for all areas, including Turnagain Pass, there is an older weak layer we are continuing to track. This is the MLK Jr buried surface hoar 1.5’-3’ below the surface. It's good to keep in mind this layer remains as well as the various layers of facets and crusts in the thinner snowpack zones. Keeping up on our safe travel protocol, including exposing one person at a time and watching our partners is key. 


Additional Concern

Glide Avalanches

New glide cracks are opening up around our region. The last known release was on the south side of Goat mountain in Girdwood Valley on Tuesday. The best way to manage this problem is to avoid traveling on slopes directly below glide cracks. A short list of known cracks in popular zones:  Magnum, Lipps, Seattle Ridge, Eddies, Lynx Ck. Keep your eyes out for these! 

 

 

   

Magnum glide crack that has been slowly opening for over a month now. It is unknow whether this crack will release or not, it's always best to hedge our bets and limit exposure under this and any other crack. (photo: Duncan Wright)


Mountain Weather

Yesterday:  Sunny skies were over the region with light and variable winds along ridgetops. Daytime temperatures were near 30F at sea level and near 20F along ridgetops. Overnight an impressive inversion has set up. At sea level and in valley bottoms temperatures have dropped to the single digits, while ridgetop temperatures continue a slow rise into the 20'sF. 

Today:  Another round of sun with light and variable ridgetop winds are on tap. Temperatures should recover into the teens in valley bottoms before cooling back down tonight. Upper elevation temperatures should continue a slow rise into the mid 20'sF. 

Tomorrow:  A ridge of high pressure has built over Southcentral is entrenching itself for the foreseeable future. We can expect sunny skies with gradually warming temperatures for the next 5 days or more. We could see very springlike conditions at mid to upper elevations as temperatures climb to 30F by Monday.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 20  62 
Summit Lake (1400') 12  30 
Alyeska Mid (1700') 18  57 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 17  Variable  18 
Seattle Ridge(2400') 20  Variable 

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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