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Avalanche Advisory

Turnagain Area Avalanche Advisory
Monday, December 10th 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. As easterly winds continue today triggering a wind slab in steep leeward terrain will be possible. Watch for changing conditions. If snow amounts are higher than forecast expect danger to rise to CONSIDERABLE and human triggered avalanches to be likely. 

SUMMIT LAKE:  A very weak and shallow snowpack exists under the recent storm snow. Slab avalanches 1-2' deep may to be easy to trigger on steeper 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.
1 Low Treeline / 1,000'-2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Special Announcement

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

Looking for avalanche courses or evening presentations? Check out our calendar page! There are two CNFAIC evening discussions coming up - these are FREE and a great way to get your head back in the avalanche game. This week - 'Tales from the Pit' at Blue & Gold Boardshop in Anchorage!

 


Avalanche Problem 1

Wind Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
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Size

Easterly winds blowing 15-30 mph with gusts into the 50s overnight will have moved any soft storm snow left available to transport into leeward areas. Additional snow falling today may also get blown around with 1-4" in the forecast. Wind effect from the very strong winds during the wet storm on Friday and Saturday was evident in the Alpine yesterday. However, there was minimal signs of wind slab. Today that may have changed, wind-loaded, steep unsupported slopes above 2500' may be tender.  Look for stiff, pillowed snow and cracking and listen for hollow, drum-like sounds. Loading patterns can be very localized and it is crucial to look for clues indicating where the snow is being distributed. 

Wind effect on the Tincan uptrack, 12-9-18

 


Additional Concern

Persistent Slabs

Observations yesterday in Turnagain Pass found signs that the storm snow is bonding well to the old snow surfaces. We do not have evidence that there currently is a persistent weak layer issue in the this core area of the advisory zone. Above 2,500' there is a thin layer of buried surface hoar anywhere from 2-5' deep in the snowpack but it is not showing signs of reactivity and at this point is being regarded as a dormant layer to track.  As we move south and the snowpack is shallower, the potential to trigger a persistent slab avalanche on weak snow near the ground increases. Observations prior to the storm showed weak facets in Summit Lake. If traveling in this area the likelihood of triggering a dangerous avalanche remains. Choose terrain carefully.

Red flags to watch for:
-  Recent avalanches 
-  Whumpfing (collapsing) of the snowpack, a sign to avoid avalanche terrain.
-  Shooting cracks, likely to be seen near ridgelines where the wind has formed wind slabs.

 

Summit snowpack observation: Tenderfoot, 12-3-18


Mountain Weather

Yesterday: Skies were mostly clear and sunny. Temperatures were in the 20Fs to mid teens. Winds during the day were light and variable. Overnight easterly winds picked up blowing 15-30 mph with gusts into the 50s. Temperatures initially cooled into the evening and then rose again in the early morning into the 20Fs and low 30Fs. 

Today: Cloudy skies and snow showers throughout the day. 1-4" of snow above 300'.  Easterly winds 10-20 mph with gusts into the 30s. Temperatures in the low 30Fs to mid 20Fs. Continued snow showers overnight with snow to sea level, 2-5". 

Tomorrow: Continued snow showers with more cold air moving into the region Tuesday night. From the National Weather Service: The colder air which moved across the Gulf and Southcentral yesterday was the beginning of what appears to be a prolonged shift to a more "typical" Alaska weather regime for this time of year. There are a number of features in the forecast that we will keep tabs on for the week! Stay tuned. Timing and precipitation amounts are still uncertain. 

*Seattle Ridge anemometer (wind sensor) is rimed over and not reporting. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 24   0.1  26  
Summit Lake (1400') 19   0  
Alyeska Mid (1700') 24 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 14  NE  12  53 
Seattle Ridge(2400') 20  *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: 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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