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Avalanche Advisory

Turnagain Area Avalanche Advisory
Sunday, January 7th 2018 5:09 am by Wendy Wagner
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche danger remains CONSIDERABLE for the travel advice portion of the danger scale. Triggering a slab avalanche 1-3' thick at elevations 2,000' and higher is possible and may still be likely in places. Additionally, triggering a larger slab breaking near the ground remains possible at elevations above 3,000'. Careful snowpack evaluation, cautious route-finding and conservative decision-making are essential in the Alpine. Sticking to low consequence terrain 30 degrees and less, and out of runout zones, is recommended above 2,000' to simply avoid these issues. The danger is MODERATE between 2,000-2,500' and a LOW danger exists below 2,000'.


 Show the Complete North American Avalanche Danger Scale
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
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.
Special Announcement

Turnagain Pass is open to motorized use. Special Avalanche Bulletin has been issued this weekend due to an unstable snowpack in an area with little information combined with anticipated crowdsThe Chugach National Forest wants to remind riders to avoid areas with thin snow cover like “Rookie Hill” and the Southern end of Turnagain Pass towards Bertha Creek. Johnson Pass remains closed due to lack of snow. 

*Coming up January 13th 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

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Several days of generally quiet weather is allowing the snowpack to slowly adjust and theoretically avalanches are becoming less likely to trigger. There was a spike in Easterly winds on Friday afternoon that loaded certain slopes, but other than this no load has been added since Wednesday. Time is on our side, but with that said, we have several weak layers in the snowpack. The pack is getting to the point it may not show any signs of instability until an avalanche is triggered. Many folks may ride/ski a slope before someone hits just the wrong spot. It's a tricky situation. 

Points to keep in mind if you are headed out today and the visibility opens enough for travel above treeline:

1-  Slab avalanches 1-3' thick will be possible to trigger, and may even remain likely to trigger on certain slopes
2-  The snowpack is likely to 'feel' stable and not show its cards till it's too late (several tracks may be on a slope before it releases)
3-  Safe travel protocol is key to stacking the odds in your group's favor if choosing to ride upper elevation avalanche terrain (i.e., exposing one person at a time)
4-  Avalanches triggered can be large and unsurvivable

Over the past week we have been concerned about a layer of buried surface hoar that sits 1-3' deep (buried by the New Year's storm). This layer remains reactive in pits between 2,000-3,200', yet it remains untested at the higher elevations. We are also concerned about a layer of faceted snow that sits near the ground on slopes that avalanched in early December. Both these issues are in the top three feet of the snowpack and are responsible for these 'persistent slab' avalanche problems. Quick note of thanks to the many folks writing in to help us assess the layers!

Plumes on the Twin Peaks near Silvertip, created by Easterly winds on Friday afternoon.


Snowpack just above treeline on Tincan - buried surface hoar main concern for human triggered avalanches


Many tracks on a slope - snow is complex, we know there are weak layers lurking, don't assume the slope next door will allow that many tracks.


Seattle Ridge, just open to motorized use - very little information for this zone, please let us know what you see if you head this way!


Avalanche Problem 2

Deep Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

In the Alpine, above 3,000’, human triggered large and dangerous deep slab avalanches are still possible. Weak sugary snow (basal facets) near the ground is creating a low probability/high consequence avalanche problem that is impossible to outsmart. This will take a long time to heal. A big trigger like a snowmachine or a slab avalanche in the upper layers of the snowpack may be enough force to initiate a deep slab avalanche. Likely trigger spots will be in thinner areas of the snowpack that are connected to large, loaded slopes. Cautious route-finding is essential. This includes thinking about the remote trigger potential from below.


Additional Concern

Changes coming to this advisory page tomorrow! Please see this short document and video about the changes and reasons for them.

 


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Mountain Weather

Mostly cloudy skies were over the region yesterday with light precipitation falling early in the day. Around an inch of new snow was seen in most places with period of light rain at sea level. Temperatures were in the mid 20'sF along ridgetops and 32F at 1,000'. Ridgetop winds were light from the East in the 5-10mph range. 

Today, expect mostly cloudy skies with possible breaks in cloud cover. Scattered snow flurries could fall in places higher than 700' with light rain below. Winds will be light and variable. Temperatures should reach 30-32F at 1,000' and remain in the mid 20's at ridgetops.

Monday and Tuesday look to be a true break in weather with mostly sunny skies. Wednesday is a chance for more flurries, but little accumulation expected. The next 'real' chance for snow may come this weekend. 

*Seattle Ridge anemometer is rimed and not reporting.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 31  43 
Summit Lake (1400') 26  16
Alyeska Mid (1700') 30   0.06 38 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 23  NE  27 
Seattle Ridge(2400') 26  *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, 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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