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Avalanche Advisory

Turnagain Area Avalanche Advisory
Monday, December 3rd 2018 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 MODERATE above 2500’ in the Alpine. Human triggered slab avalanches up to 1-3’ thick remain possible due to a weak layer of snow under the Thanksgiving weekend storm snow. Additionally, watch for lingering wind slabs in steep wind-loaded terrain.

 


 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.
1 Low Treeline / 1,000'-2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
0 NO RATING Below Treeline / Below 1,000'
Special Announcement

New snow and wind has increased avalanche conditions in many zones outside of the Chugach National Forest. 


Avalanche Problem 1

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

In the Alpine, sitting anywhere from 1 to 3' below the snow surface, is a thin layer of weak snow (buried surface hoar/BSH). An observer yesterday found this layer to still be reactive in a snowpit on Sunburst right around 2500'. This buried weak layer remains a concern. At this point obvious signs of instability may not be observed but the possibility of triggering an avalanche cannot be ruled out. As always use safe travel protocol and choose terrain with consequences in mind i.e. where is the avalanche path and where would I end up if the slope slides? The snowpack profile below illustrates the slab sitting over the weak layer.

 

         

 Snowpit on Sunburst, December 2, 2018. Observer: Chris Robertson 

  Snow cover looking south on Turnagain Pass, December 2, 2018. Photo: Allen Dahl


Avalanche Problem 2

Wind Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Be on the lookout for wind slabs in steep unsupported terrain. Strong easterly winds on Saturday afternoon may have loaded leeward slopes in the Alpine. It may still be possible to trigger a lingering pocket that could be dangerous. Look for stiff, pillowed snow and cracking and listen for hollow, drum-like sounds. 


Mountain Weather

Yesterday: Skies were overcast and there were very light rain/snow showers. Temperatures were in the mid 30Fs to mid 20Fs. Winds were easterly 10-20 mph with gusts into the 30s. 

Today: Cloudy skies in the morning becoming partly sunny. Temperatures will be cooling from the 30Fs into the lower 20Fs as skies clear and colder air moves over the region. Winds will be northeasterly 5-15 mph with gusts into the 20s. Expect overnight temperatures in the low 20Fs and high teens. Clouds will move back in overnight. 

Tomorrow: Chance of snow showers and increased easterly winds in the afternoon as the next front moves over the area. The pattern remains active through the week. As usual the temperatures and timing are uncertain. Stay tuned!

*Seattle Ridge wind sensor is rimed over.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 33  1 0.1 13 
Summit Lake (1400')  29   3 0.3 2
Alyeska Mid (1700')   33    0 0.19  N/A

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 24  NE  11 32 
Seattle Ridge(2400')  29   *no data *no data  *no data 

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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