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Avalanche Advisory

Turnagain Area Avalanche Advisory
Friday, January 12th 2018 5:10 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 HIGH at all elevations above 1000’ due to a storm bringing new snow, strong winds and warm temperatures to our region. Natural and human triggered storm slabs 1-3’ deep will be likely today in avalanche terrain and may step down to an older more dangerous week layer. Travel is not recommended on slopes steeper than 30 degrees and in all runout zones. 

The avalanche danger is CONSIDERABLE below 1000’ where natural avalanches from above are possible in steep channeled terrain.  

**Portage and Whittier, outside of our advisory zone, are expected to receive double the amount of precipitation as Turnagain Pass. Avalanche activity in these zones may run to valley bottoms.   


 Show the Complete North American Avalanche Danger Scale
4 High Alpine / Above 2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4 High Treeline / 1,000'-2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
3 Considerable Below Treeline / Below 1,000' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
Special Announcement

Our advisory page has changed! Information on the changes can be found HERE

*Tomorrow, January 13th, there is a FREE avalanche rescue clinic at Hatcher Pass. Practice with your gear on your way to the backcountry - clinic runs from 11am - 1:30pm. 


Avalanche Problem 1

Storm Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Overnight a foot of new snow has fallen in the upper elevations of Turnagain Pass and Girdwood and another 10-20” of snow is expected today. This new snow combined with strong Easterly winds and warming temperatures will be forming unstable storm slabs and adding stress to preexisting weak layers within the snowpack. This new snow has fallen on surface hoar and near-surface facets and slabs are expected to be sensitive and easy to trigger. Below 2000’ these weak layers are sitting on a slick crust and could catch you by surprise in more protected areas and on small terrain features. Stormy weather today will be increasing the avalanche hazard, as slabs grown in size, and natural avalanches will become more likely as the day moves on.  Should you venture out today, stick it low angle slopes, less than 30 degrees and avoid being under the runout of larger slopes above. Shooting cracks and collapsing sounds “whumpfing” are expected and will be obvious signs the snow is unstable. This is a good day to ride in the flats and keep your terrain choices mellow. Don’t forget even small terrain feature can have high consequences. 

Shooting cracks observed yesterday during the beginning of the storm

 

 


Avalanche Problem 2

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Rapid loading due to new snow and winds will be adding stress to existing week layers within the snowpack. We have been tracking a layer of buried surface hoar from the New Year’s holiday, which still is showing propagation potential in test pits above 2500’. Triggering a storm slab could step down to this layer producing a large to very large avalanche depending on the size of the slope. In addition, a Deep Persistent Slab problem remains a concern in the upper elevations above 3000’, and serves as one of the many reason to not go into the alpine today. In fact - today is a great day to stay on low angle terrain and practice your rescue skills. 

 

Several week layers exist within the snowpack, additional reasons to avoid travel in avalanche terrain. 

 


Mountain Weather

Snow started falling yesterday morning and continued overnight with 0.7” of Snow Water Equivalent (SWE) at Center Ridge Snotel and 0.62” SWE at Alyeska Midway station. Unfortunately the Snotel site was not recording height of snow this morning, but Alyeska midway station recored 11” since yesterday.  Easterly ridgetop winds averaged in the 30’s mph with gusts reaching the 60’s mph on Sunburst. Gusty valley winds were also observed along the road corridor at Turnagain Pass. Temps gradually increased overnight with sea level temps reaching the mid 36F’s this morning and transitioning to rain just above sea level.  

Today 0.8” SWE, another 10-12” of snow is expected during the day and double this amount midnight. Winds will continue to blow from East, 20-40mph and temperatures are expected to continue to warm with high’s in the upper 30F’s at sea level. Rain/snow line is likely to bump up to 500’ by this afternoon. 

Tomorrow more rain and snow and Easterly winds are on tap as another front moves into our region. Temperatures are expected to increase into the 40Fs at sea level and rain/snow line will continue to move up in elevation, possibly as high as 1500’ by Sunday.

*New snow was estimated at Center Ridge Snotel based on similar SWE (Water inches) at Alyeska midway station. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 31  *12  0.7  *54 
Summit Lake (1400') 29  15 
Alyeska Mid (1700') 28  11  0.62  45 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 19  ENE  35  68 
Seattle Ridge(2400') 23  SE  20  41 

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
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