CNFAIC LogoCNFAIC Logo

Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Tuesday, December 11th 2012
Created: Dec 11th 6:51 am
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.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
 Show the Complete North American Avalanche Danger Scale
The Bottom Line

BOTTOM LINE

There is a MODERATE avalanche danger today for wind slab avalanches above treeline. Human triggered avalanches are possible on steep slopes (greater than 35 degrees) where the high winds from Saturday night's storm created sensitive slabs and drifts.These wind slabs are sitting on a persistent weak layer of faceted snow that is keeping avalanche potential possible. Any slide triggered today has the potential to be dangerous if released in high consequence terrain, such as large bowls and above cliffs and gullies. Below treeline there is a generally LOW avalanche danger as the snowpack consists of mostly loose unconsolidated snow.


Primary Concern

There were no new avalanches reported yesterday after the plethora of easily human triggered avalanches on Sunday. This is likely due to two things: (1) only a handful of folks were out testing slopes that were not already tested Sunday and (2) the weak layer is slowly adjusting to the new load of the wind slab. The widespread collapsing seen Sunday has decreased but was still occurring on the ridgelines yesterday, which points to the lingering instability. Snowpack test results show signs the slabs are gaining strength - moderately easy to trigger (compared with Sunday when it was just plain easy to trigger).

Areas where the Saturday winds loaded slopes and scoured slopes are still visible as the scoured areas have a darker look while wind drifts and slabs have a brighter, white look and often a rounded nature. A slight bump in wind today (NW, 10-20mph on the ridgelines) will likely not add to the avalanche problem but may mask these older, more concerning wind slabs. Any wind loaded slope steep enough (> 35 degrees) has the potential to avalanche, these slides could be anywhere from small and manageable to larger and unmanageable. If one of these releases in unforgiving terrain (for example, in a large bowl like Todd’s Run, or over a cliff) a ride could be enough to injure or kill a person. Watching for collapsing (whoomphing) and cracking will be obvious signs the slab is unstable.

Good travel practices are not to be left at home. Only exposing one person at a time, keeping a close eye on your partners and discussing potential avalanche zones will be prudent.

Below treeline, the snowpack is back to one unconsolidated unit with low density storm snow, which has lost its slab properties, over the weak old snow. There is a layer of buried surface hoar that does a good job at marking this new/old interface.


Mountain Weather

We have a brief break between storms today with clearing skies and light to moderate northerly winds. Temperatures have cooled off with the northerly flow overnight and are in the upper 20’s F at sea level and mid-teens at 4000ft. Ridgetop winds are forecast to be ~10mph from the NW, gusting up to 25mph.

Another system is moving in from the west tonight but it is not the ideal set up for Turnagain Pass as the low is centered north of the Aleutians – more of an Anchorage and Hatcher Pass special. It looks like Turnagain Pass could see somewhere around 4-8” of snowfall tonight through Wednesday. Stay tuned tomorrow morning.

 


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). 

Kevin will issue the next advisory Wednesday morning, December 12th.

 

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: Apr 11, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: OpenPlease park on road in and leave the turnaround (near outhouse) open for trailers to turn around.
Placer River: OpenWide swaths of open river in the Placer Valley. Travel with extreme caution!
Skookum Drainage: ClosedSKOOKUM DRAINAGE CLOSED TO MOTORIZED USE ON APRIL 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: ClosedClosed for the remainder of the 2017 season.
Seward District
Carter Lake: Open
Lost Lake Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Primrose Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Resurrection Pass Trail: ClosedClosed for 2016/17 winter season. This is a non-motorized season. This alternates every other year and will open again during the 2017/18 winter.
Snug Harbor: Open
South Fork Snow River Corridor: Open
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
© 2017 Chugach National Forest Avalanche Information Center. All rights reserved.
FCNFAIC