CNFAIC LogoCNFAIC Logo

Avalanche Advisory

Turnagain Area Avalanche Advisory
Tuesday, February 20th 2018 5:08 am by Aleph Johnston-Bloom
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
Previous ForecastNext Forecast
BROUGHT TO YOU BY
The Bottom Line

The avalanche danger is MODERATE above 1,000' on all aspects. Human triggered slab avalanches 1-2' thick remain possible. Additionally, weak layers deeper in the snowpack may still be triggered, creating a larger avalanche. Sunshine warming southerly slopes could contribute to instability today.

The Summit Lake area saw more avalanche activity last week. Take a look at the Summit Summary HERE. 

 


 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.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Avalanche Problem 1

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Persistent Slabs:  Triggering a slab avalanche 1-2+ feet thick remains our main concern. There has been mostly quiet weather and lack of people triggering avalanches over the past week. The persistent slabs are becoming more difficult to trigger with time, but a large and unmanageable avalanche is still possible. Weak layers in the snowpack below your feet or snowmachine should not be forgotten. The January 21st  layer of buried surface hoar with weak facets directly below sit 1-2' deep in the snowpack. This weak snow continues to show signs of reactivity. Red flags may not be present before a slope releases and it may not be the first person on the slope that triggers the avalanche. The most likely place to find this avalanche problem are slopes that have not seen significant traffic this season. 

Sunshine:  It's that time of year when we need to pay attention to the sun. On calm days the sun can heat up Southerly aspects enough to melt surface snow. This heating can also cause a slab sitting on a weak layer to become more reactive. Keep this in mind if you are enjoying Southerly aspects later in the day. 

Wind Slabs:  Watch for old wind slabs that could pop out on steep slopes. Steep rocky terrain where the slab is not supported from below are the most suspect. These hard slabs often break when you are out onto them. 

Cornices:  Avoid traveling under cornices and give them a wide berth on ridges as they can break back further than expected.

Snowpit from Eddies yesterday showing the January 21st layer of concern 

January 21st buried surface hoar in Eddies snowpit at 2400'

 


Additional Concern

Deep Persistent Slabs

As you plan your day, keep in mind that there are deeper persistent layers that could 'wake up' if you find the wrong spot above 3,000' in the Alpine. At these high elevations, old weak layers of facets and buried surface hoar sit in the bottom half of the snowpack. This structure is most pronounced in places with a thin overall snow cover, such as the South end of Turnagain Pass and the Summit Lake area. 

 


Mountain Weather

Yesterday was partly cloudy with skies becoming progressively clearer throughout the day. Temperatures were in the mid 20Fs to low 30Fs with a minor inversion in place. Winds were light and variable. 

Today is forecasted to be similar with the clouds that built overnight decreasing through the day and skies becoming mostly sunny. Temperatures will be in the mid 20Fs to mid 30Fs. Winds will be northerly 5-15 mph with gusts into the 20s. 

Tomorrow will be mostly cloudy. There is snow in the forecast for Thursday but precipitation amounts are still uncertain. From NWS: A fairly strong and moist trough will approach Southcentral from the west on Wednesday night and cross the area on Thursday. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 27  63 
Summit Lake (1400')  23    0    0    24  
Alyeska Mid (1700')  24    55  

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  27  WSW  6  20
Seattle Ridge(2400')  26 variable   3  8

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, 2018 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed as of April 20th
Placer River: ClosedClosed as of April 17th
Skookum Drainage: ClosedClosed as of April 1st.
Turnagain Pass: ClosedClosed as of May 7th. Happy summer, see ya when the snow flies!
Twentymile: ClosedClosed as of April 13th
Seward District
Carter Lake: ClosedClosed as of 4/27
Lost Lake Trail: ClosedClosed as of April 13th
Primrose Trail: ClosedClosed as of April 13th
Resurrection Pass Trail: ClosedClosed as of April 20th
Snug Harbor: ClosedClosed as of 4/27
South Fork Snow River Corridor: ClosedClosed as of April 13th
Summit Lake: ClosedClosed as of April 20th

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
© 2018 Chugach National Forest Avalanche Information Center. All rights reserved.
FCNFAIC