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Avalanche Advisory

Turnagain Area Avalanche Advisory
Friday, November 30th 2018 7:00 am by Heather Thamm
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’ where triggering a slab 1-3’ thick is possible on slopes steeper than 35 degrees. Be aware of changing weather and wind slabs forming late afternoon.

At treeline (below 2500’) the avalanche danger is LOW where a strong crust has formed and capped the snowpack.

 


 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 on 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

In the alpine a thicker snowpack exists and with it more uncertainty.  Observers yesterday found depths to be in the 3-5’ range near 3000’. Two pit locations above 3000’ (on Tincan & Sunburst) found a layer of surface hoar buried 2-3’ below the surface. One party on Sunburst felt a collapse ‘whumpf’ around 2800’ along the West ridge and several large piles of debris were noted on steep Northern terrain from avalanches earlier in the week.

What does this all mean?

Triggering a large persistent slab is possible in steep terrain and will be more likely in thinner areas of the snowpack. It remains unknown how widespread this layer is across our region or how much avalanche activity occurred on it early in the storm that may be hidden. It may be more likely to trigger a persistent slab in places that received less overall precipitation like the Southern end of Turnagain Pass and Summit Lake. Persistent weak layers are tricky and hard to manage. Evaluate your consequences and choose conservative terrain. Be on the lookout for any obvious signs on instability like whumpfing, shooting cracks or any new avalanche activity.

 

Several snowpits dug in the upper elevations yesterday found buried surface hoar

 

Rollerballs and a small mid storm avalanche were visible yesterday. This visual is a little deceiving. Loose snow is covering a thin crust, but gradually disappears around 2700'. 

 

A strong crust has formed below 2500’ but the snowpack remains very thin to nonexistent below 1500'.


Avalanche Problem 2

Wind Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Easterly winds are expected to increase to Moderate (15-25mph) late afternoon and into the evening. In the alpine there is snow available for transport and triggering a shallow wind slab on leeward features may be possible. Pay close attention to changing weather and be on the lookout for shooting cracks and drifting snow.


Mountain Weather

Yesterday: Temperatures remained below freezing with ridgetops near 15F most of the day and mid 20F’s near 1000’. Winds were light and variable. No measureable amount of precipitation fell.  Skies were broken in the morning becoming overcast in the afternoon.

Today: Winds are expected to be light and variable in the morning shifting to an Easterly pattern and increasing to Moderate (15-30mph) by tonight. Temperatures are expected to remain below freezing in the mid and upper elevations for today. Scattered snow showers are possible in the upper elevations and skies will be overcast.  

Tomorrow:  Saturday temperatures are expected to rise as a second front moves up Cook Inlet. Rain/snowline may push as high as 1500’ by late morning. A few inches of snow is possible above this elevation and rain showers at lower elevations. Easterly ridgetop winds will remain Moderate (15-25mph) through Saturday evening. 

*Seattle Ridge weather station stopped collecting wind data at 10 pm on Nov 27, 2018. *Center Ridge weather station depth sensor showed 2" increase, but no actual accumulation occurred.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 24  0 *10
Summit Lake (1400') 19 
Alyeska Mid (1700') 25   *N/A

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 15  Variable  11 
Seattle Ridge(2400') 21  *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
If you have comments or questions regarding CNFAIC operations or winter recreation management, please email staff@chugachavalanche.org
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