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Avalanche Advisory

Turnagain Area Avalanche Advisory
Saturday, April 20th 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 is MODERATE for avalanches composed of the 6 - 12+" of new snow. On Northerly slopes above 2,500' dry slab avalanches 6-18+" thick will be possible to trigger. On Southerly facing slopes and all aspects below 2,500' wet loose avalanches are possible with daytime warming and solar radiation. Give cornices a wide berth and limit travel under glide cracks. The avalanche danger is expected to rise overnight and into Sunday as a warm storm moves in.

PORTAGE VALLEY: Cornice fall and/or avalanches from above have the potential to send debris to valley bottoms. Traveling along summer hiking trails, such as the Byron Glacier Trail with steep slopes overhead is not recommended on rainy/snowy days or on sunny afternoons.

WHITTIER: Between 1-2 feet of new snow has likely fallen at the upper elevations in the Whittier Glacier region. Heads up as large human triggered avalanches are possible.

LOST LAKE / SEWARD: Similar to Turnagain, dry slab avalanches could be a concern on high elevation northerly slopes.


 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.
0 NO RATING Below Treeline / Below 1,000'
Special Announcement
  • Advisories: For the remainder of April, avalanche advisories will be posted 4 days/week (on Tues, Thur, Sat and Sun). The avalanche center will close for the season on Saturday, April 27th when we will post our springtime tips. Thank you everyone for tuning in!
  • Winter has returned to Hatcher Pass with elevated avalanche danger. Be sure to check out today's Saturday HPAC forecast if you are headed that way!

Avalanche Problem 1

Storm Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Anywhere between 6-16" of new dry snow has fallen over the past 36 hours across the region. Girdwood Valley seemed to have picked up the most snow, with over a foot accumulating at the high elevations. Turnagain Pass and Summit Lake have both seen around 6-8" of new snow. Easterly ridgetop winds have been 15-25mph, which is enough to load leeward slopes. That said, avalanche concerns will be relegated to the new snow. How much snow fell in the area you travel, how much wind loading occurred and how the new snow is bonding to the underlying surfaces are the questions today. High elevation northerly aspects are the most suspect for poor bonding as the new snow fell onto weak older snow and possibly surface hoar. If you are headed out today in hopes of the clouds breaking, keep the following in mind:

  • Dry slab avalanches up to a foot thick could be triggered on steep northerly slopes
  • Wind loaded slopes are more concerning as slab depths could be greater (1-2' feet)
  • Listen/feel for collapsing in the new snow
  • Watch for cracking in the new snow 
  • Quick hand pits are great ways to assess the new snow/old snow bonding

Avalanche Problem 2

Wet Loose

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

On all Southerly facing slopes and slopes below 2,500' we can expect the new snow to stick rather well to the old soft/warm crusts. The concern here will be daytime warming and sunshine. Roller balls and wet loose sluffs should be expected as the new snow heats up and begins to roll and sluff off the mountainsides. The size of potential sluffs will be determined by the amount of new snow. Wet sluffs could become quite large and dangerous on slopes with up to a foot or more of new snow.

CORNICES: There are still large cornices along ridge tops. Give them lots of space as they can break farther back than expected. 

GLIDE AVALANCHES: It's been close to two weeks since our last known glide avalanche, but keep in mind glide cracks are continuing to creep down-hill. As always, limit traveling under their runout. They are unpredictable and can avalanche at any time. 


Mountain Weather

Yesterday:  Roughly 6-10" of new snow fell over the region at all elevations late Thursday and early Friday morning, favoring Girdwood Valley. Light showers continued through the day adding another 1-3". Ridgetop winds over the past 24-hours have been easterly 15-25mph with gusts to 40mph. Temperatures have been in the 20'sF along ridgetops and near 30F at 1,000'. 

Today:  Clearing skies and lingering clouds are expected today before a third round of precipitation pushes in tonight. Ridgetop winds should be in the 10-20mph range from the east today and bumping up to the 30's tonight. Temperatures are on a warming trend and may reach 40F at 1,000' today with ridgetops in the upper 20'sF. 

Tomorrow:  Stormy wet weather is on tap. Rain up to 1,500 - 2,000' is expected tomorrow with 6-12" of snow above this. Up to 16" of snow could fall in favored areas such as Portage Valley and Girdwood. Ridgetop easterly winds will be in the 30-40mph range with gusts over 50. Unsettled and wet weather looks continue into the workweek.


Thanks to our NWS partners for their graphic of QPF (Quantitative Precipitation Forecast), which is the water amount expected through Sunday. A general rule of thumb is 1" of water = 10" of snow. Of course it has to cold enough for snow and this event is expected to bring rain up to 1,500' with snow falling at the higher elevations.


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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 34  0.2  65 
Summit Lake (1400') 32  0.3  20 
Alyeska Mid (1700') 30  0.4  62 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 20  SE  15  40 
Seattle Ridge(2400') 25 *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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