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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Thursday, January 7th 2016
Created: Jan 7th 5:44 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.
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.
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The John Byrne Family
Special Announcement

The Hatcher Pass Avalanche Center has completed an avalanche accident report following the recent death of a snowmachiner that occurred on January 2nd. Click HERE for the report.

Tonight Wendy Wagner, CNFAIC forecaster and director, will be giving our final Fireside Chat on snowpack and weather. It will be in Anchorage at the Alaska Avalanche School at 6:30pm.

On Saturday CNFAIC forecasters are hosting a Hands-on Avalanche Rescue Workshop from 11:00am to 12:30pm at the motorized lot on Turnagain Pass.

*All events are free to the public!  

Filing for the PFD this week? Remember, The Friends of the CNFAIC is part of PICK.CLICK.GIVE. Your donations are greatly appreciated and an integral part to making the CNFAIC possible and sustainable.


The Bottom Line

Today the avalanche danger is MODERATE both at Treeline and in the Alpine. Triggering a fresh windslab 4-8” thick is possible today near ridgetops and on leeward features. Be on the look out for hollow sounding snow, shooting cracks, and blowing snow. Be aware of large cornice features and recent glide crack movement and avoid putting yourself on or under these unpredictable hazards.

Below 1000’ the avalanche danger is LOW where triggering an avalanche on a hard supportable crust is unlikely.

*Outside of our forecast zone in Summit Lake where a generally thinner snowpack exists triggering a slab 3’ thick is a concern. Cautious route-finding and careful snowpack evaluation is advised. 


Primary Concern

Overnight Easterly winds increased into the 20’s with gusts in the 30-40’s mph and moderate winds are expected to continue today. With 6-10” of low-density surface snow available for transport, isolated winds slabs are possible on leeward features. These slabs are expected to be small (4-8” thick), but if triggered in steep terrain, could send you for an unintentional ride.

Older winds slabs from the holiday storm event may still be lingering in very steep terrain, but otherwise this problem is becoming less likely as we move away from the storm. Yesterday a generally stable snowpack was observed where older wind affected snow was stabilizing quickly.

Ease into steep terrain today and pay attention for hard hollow sounding snow and shooting cracks. If you see snow being transported off of ridges be very aware of the consequences below you. 


Secondary Concern

Today’s secondary concern is Cornice Fall and Glide Cracks!

Very large cornice features have formed throughout the region as a result of a two-week storm that deposited ~9’ of snow and was accompanied by very high winds. Cornices have the potential to fall naturally or be triggered by the weight of a person or machine and can be very dangerous. Travel under or on them should be avoided. They have the tendency to break farther back from the ridge than expected and can trigger an avalanche on the slope below by adding a lot of weight quickly. As you approach ridgelines and the entrances to backcountry bowls make sure you aren't accidently traveling on overhanging snow. 

Glide cracks are appearing throughout the forecast region (Girdwood to Turnagain Pass.) These cracks appear to be opening fast and are very unpredictable. Similar to managing a cornice, it is best to avoid traveling on or under slopes with glide cracks. Although triggering one of these is uncommon, should one release above you, consequences would be high. 

Significant moat at least 5 meters back from cornice on Seattle Ridge near the top of uptrack. At least one sled track took a quick dip. Photo by Paul Forward

 

Ski tracks above two glide cracks on Lipps SW face. These glide crack have recently opened and were not present a week ago.

 


Additional Concern

In some parts of the advisory area 5-7' of settled storm snow is sitting on a layer of old faceted snow on top of the Thanksgiving Rain Crust. This still needs to be a consideration as you travel into the backcountry today. This is a low probability, very high consequence set-up.  It is important to use safe travel practices and do not overload slopes with multiple skiers, boarders or snowmachines. Limit your exposure time spent underneath large paths.

On the Sourthern periphey of our forecast zone such as Johnson Pass and Lynx Creek we have limited snowpack information. But we do know in Summit Lake, the snowpack is shallower and harbors more weak layers under the recent storm snow.  See Wendy’s observation and write-up from a snowboarder-triggered avalanche (Saturday) that failed on a buried surface hoar layer.

Watch for signs of instability: recent avalanches, shooting cracks, collapsing and whumpfing. Pay attention to snow depth and trigger points. Deep slabs are most easily triggered from shallow spots where the weight of the traveler can more easily affect the weak layer. 


Mountain Weather

Yesterday skies were clear and temperatures were in the 20’s F. Light ridgetop winds were from the West.

Overnight Easterly winds increased into the 20’s mph. This morning increasing temperatures were 32F at 1000’ at Turnagain Pass. No precipitation was recorded overnight.

Today showery conditions are forecasted for mountain areas near the coast. This will likely be light rain below 1000’ near Girdwood and Portage and periods of light flurries are possible today in Turnagain Pass. Not much accumulation is expected. Easterly Ridgetop winds will remain in 15-30mph range throughout the day.

Friday night into Saturday another storm is expected to bring warm temps and more precipitation. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 28  83 
Summit Lake (1400') 25  26 
Alyeska Mid (1700') 28  61 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 23   NE 11  40 
Seattle Ridge(2400') 25  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: 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

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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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