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Avalanche Advisory

Turnagain Area Avalanche Advisory
Sunday, January 13th 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 CONSIDERABLE on slopes above 1,000'. Natural avalanches due to strong wind and several inches of new snow are possible in the Alpine and in areas exposed to wind in the Treeline. Human triggered slab avalanches, up to a foot thick or more, will be likely and may be triggered remotely. Pay attention to new snow amounts and wind effect. Avoid being in runout zones from avalanche paths above you. In addition, glide cracks may release into avalanches; limit/avoid exposure under them. 

SUMMIT LAKE / JOHNSON PASS:  Keep in mind buried weak layers exist in the middle and base of the snowpack. More potential for triggering a large slab avalanche exists in this zone, especially with wind-loading. Choose terrain wisely.

OVERHEAD HAZARDS:  Heads up! Roof avalanches are expected near sea level in Girdwood, Portage and other areas where temperatures are rising to 40 degrees F.


 Show the Complete North American Avalanche Danger Scale
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
3 Considerable Treeline / 1,000'-2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
2 Moderate Below Treeline / Below 1,000' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
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Avalanche Problem 1

Storm Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
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Size

The first in a series of storms is over the region today. Snowfall began yesterday and as of this morning, roughly 2-4" has fallen with up to 5" or more in the Girdwood and Placer Valleys. An additional 2-4" is expected over the course of the day. Although snowfall amounts are meager to what some of us may have hoped for, the winds are producing. Ridgetop winds have been blowing strong from the east (20-30mph with gusts to 50) for almost 24-hours now. The other producer is the temperature. Temperatures have risen as much as 40 degrees F in the last 24-hours. The minus single digit conditions felt in valley bottoms are now in the tropical 30'sF. These are all abrupt changes to the snowpack and avalanche danger has risen. 

There was one suspected natural 2' slab avalanche yesterday in the Johnson Pass/Center Creek area and more of these could occur today. There is very weak snow (sugary facets and surface hoar that formed during our cold/clear period), which will cause any new slab to be very touchy. Watch for shooting cracks and recent avalanches, these are Red Flags that an avalanche will be easy to trigger.

Wind Slabs:  With little new snow to work with, the winds will also be transporting the older loose snow surface into sensitive wind slabs. Slabs are likely to be in the foot thick range in general, but could reach as thick as 2-3' along the tops of ridgelines. They should range from soft to stiff and could be triggered remotely.

Storm Slabs:  Warming temperatures are causing an upside-down storm, which will create shallow storm slabs in areas outside of the wind. Again, watch for cracking and carefully evaluate the storm snow. 

Cornices:  Cornices are growing and the warmth can help weaken them. Cornice falls are possible and may trigger slabs under them. 

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Avalanche Problem 2

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
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Size

South of Turnagain - Johnson Pass/Summit Lake zone:  As new snow and wind loading increases it becomes even more critical to remember that a poor snowpack structure exists in these areas. The Christmas buried surface hoar has been found as well as concerning facet/crust combinations in the bottom of the snowpack. Avalanches may initiate near the ground and be quite dangerous. If you're headed this way, evaluate terrain exposure and the snowpack as you travel. Be on the lookout for signs of instability. 


Additional Concern

Glide Avalanches

Glide cracks are likely to become hard to identify with snow/wind filling them in. Known areas with cracks are the southerly facing slopes on Eddies, Tincan, Sunburst, Magnum, Cornbiscuit, Lipps, Johnson Pass, Girdwood Valley and a few on the easterly slopes on Seattle Ridge. Not to mention the Lynx creek glide extravaganza. Avoiding/limiting time under these features is prudent as they can release into an avalanche at any time and are completely unpredictable. The rapid temperature rise and additional snow load over the next few days may or may not cause an increase in glide activity. 


A large glide crack near the head of Lynx creek drainage (seen yesterday 1/12) threatens a popular area to ride.


Mountain Weather

Yesterday:  Overcast skies, light snow showers and rapidly warming temperatures were over the region. Snowfall picked up overnight with 1-4" accumulating so far - higher amounts seen in Portage Valley and at Alyeska in Girdwood. Ridgetop winds have been strong from the east, averaging 20-30mph with gusts to 50mph. Temperatures rose from single digits to 40F at sea level, 32F at 1,000' and into the 20's F along ridgetops over the past 24-hours.

Today:  Snow showers should remain over the area today adding an additional 1-4' with another 1-4" overnight. Again favored areas are Girdwood and Portage Valley. Temperatures are slated to keep climbing and the rain/snow line may reach 1,000' by this afternoon and up to 1,500' by tomorrow morning (#thinkcoldthoughts!). Ridgetop winds will remain strong, 20-30mph from an easterly direction with gusts into the 50's and 60's mph. 

Tomorrow:  Precipitation should continue through Monday with light rain up to 1,500' and light snow showers above 1,500'. An active weather pattern bringing additional warm and wet weather is expected for the remainder of the week with a possible surge late Tuesday into Wednesday. 

*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') 27  0.2  53 
Summit Lake (1400') 21  1-2  0.1  21 
Alyeska Mid (1700') 26  0.27  43 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  18 NE  22  51 
Seattle Ridge(2400') 24  *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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