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Avalanche Advisory

Turnagain Area Avalanche Advisory
Saturday, December 1st 2018 7:00 am by Wendy Wagner
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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BROUGHT TO YOU BY
The Bottom Line

MODERATE avalanche danger exists above 2500’ in the Alpine. Triggering a slab avalanche 1-3’ thick remains possible due to a layer of buried surface hoar under the Thanksgiving weekend storm snow. Additionally, watch for increasing winds today from a southerly direction that may form wind slabs in unusual places.


 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

The Friends of the CNFAIC have two scholarships dedicated to avalanche education. The funds generated to make these possible are in celebration of Rob Hammel and Amy Downing, their love and passion for the mountains, and to help others stay safe. We encourage you to read each one and apply if you fit the need, or pass along to someone who could benefit. Applications due today - Dec 1st.

Rob Hammel Scholarship Fund – For recreational users and professional avalanche workers.

Amy Downing Scholarship Fund – For recreational users.


Avalanche Problem 1

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

The mountain snowpack was tested yesterday with Mother Nature's violent shake down. The Nov 30th 7.0 earthquake rocked the region. Luckily visibility was good enough to get eyes on some of the aftermath. Girdwood Valley was the most exciting as large slabs were triggered along with rock fall. Turnagain Pass fared better, as most the snowpack stayed intact. The most notable slabs on Turnagain were on the east facing slopes of Twin Peaks. Otherwise there were some shallow slabs on the southern end of Seattle Ridge and small cornice falls along ridgetops. 

What does this say about the snowpack? Well, the storm snow from last weekend that fell on buried surface hoar (a weak layer) and in some areas old weak snow, is definitely adjusting - the snowpack did not totally shake off the mountainsides. One can deduce that triggering a large avalanche is becoming less possible. Despite this, keeping in the forefront of our minds that a weak layer sits 1-3' below the snow surface is still essential. Safe travel protocols and watching our partners shouldn't be forgotten. Additionally, any signs telling us a slope could be unstable are not likely to be seen. 

 

Earthquake triggered avalanches in upper Goat Mt and Goat Couior in the Girdwood Valley

 

Magpie Peak in the upper Crow Creek Valley - avalanche debris and some slabs seen triggered by the earthquake

 

 

Rock fall off peak 4710', north aspect

 

 

Rockslide off the east face of Rainbow Peak in Chugach State Park - triggered by earthquake


Avalanche Problem 2

Wind Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Winds are slated to bump into the 40's mph today from a southerly direction along the ridgetops. This is an unusual flow direction. Watch for terrain forcing to shift winds either westerly or easterly. Be on the lookout for how winds may be transporting snow and avoid any fresh wind drifts or slabs that may form. Above 2,500' there is loose snow available for transport plus a possible 1-3" of snowfall today. 


Mountain Weather

Yesterday:  Partly cloudy skies were over the region with a few snowflakes falling last night, adding a trace. Temperatures have been steadily in the 20'sF and teens at the high elevations. Light and variable winds yesterday turned easterly overnight, with a bump in speed to 15mph with gusts to 30mph.

Today:  Light snowfall with 1-3" accumulation is expected today before diminishing tonight. Temperatures should rise significantly, turning snowfall to rain as high as 2,000' by the afternoon. Cross your fingers the cool air stays in place! Winds are forecast to increase up to 40mph from the SW with stronger gusts, also diminishing to the 15-20mph range tonight.

Tomorrow:  Another band of precipitation is expected to move through tomorrow. This one is expected to be cooler, bringing a chance for a few inches of snowfall to lower elevations. 


*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') 26  Trace  10 
Summit Lake (1400') 26  0.1 
Alyeska Mid (1700') 27 Trace  0.03 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 19  NE  31 
Seattle Ridge(2400') 23   *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

Subscribe to the Turnagain Area Avalanche Advisory:

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
© 2019 Chugach National Forest Avalanche Information Center. All rights reserved.
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