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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Wednesday, January 28th 2015
Created: Jan 28th 5:48 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.
0 NO RATING Below Treeline / Below 1,000'
 Show the Complete North American Avalanche Danger Scale
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Special Announcement

Join CNFAIC forecaster John Fitzgerald for an evening of general avalanche awareness and a discussion on the state of the snowpack at Turnagain Pass!  This event will be held on Tuesday, Feb.3 at REI in Anchorage from 6:00pm to 7:30pm and is FREE. See Calendar for detials


The Bottom Line

Pockets of MODERATE danger are possible today as winds15-25mph could form shallow wind slabs on steep leeward terrain features in the Alpine. If winds persist these slabs could be tender enough for human triggered activity. The avalanche danger remains LOW at Treeline below 2500'.

It is important to note that shallow surface instabilities do exist in areas outside of the Turnagain Pass advisory zone. Heightened caution is advised at higher elevations above 4000’ and in areas that have had more wind exposure over the last few days like Girdwood Valley, Portage and Summit Lake.  


Primary Concern

Temperatures have been relatively cool (single digits to teens F) over the last four days. Turnagain Pass has about 4-6” of slightly aged, low-density snow available for transport. This morning winds have increased along ridgetops averaging 15mph with gusts into the low 30’s. The prominent wind direction on Seattle Ridge has been Southwesterly and Easterly on Sunburst. If winds continue as forecasted today this combination of loose dry snow and moderate winds could be just enough to form wind slab pockets up to 6” thick.  Be on the look out for tender areas of wind-stiffened snow. These shallow slabs will be small, not likely to bury a person, but could be just enough to knock you off your feet and take you for a ride in terrain steeper than 35°.

Yesterday we received a report of a skier triggered soft slab 10” deep that propagated 75’ across a Western aspect, mid-slope near 5000’.  This is outside of our normal forecast zone, but is worth noting for anyone planning to access remote terrain. Also Girdwood Valley, Portage, and Summit Lake have seen more wind exposure than Turnagain Pass in the last three days, therefore wind slab pockets could be more tender and easier to initiate on leeward features. Evaluate surface conditions as you travel today and watch for visible wind loading on terrain above you. This could be extra important for ice climbers in very steep terrain where natural wind slab avalanches could occur. 


Additional Concern

Glide Cracks

No new significant glide activity has been observed over the last week. Due to the unpredictable nature of glide avalanches it is important to get a good look at the terrain you’re about to ski/ride to avoid traveling directly on the slab of a glide. See photo below. In general be quick if traversing direcly below glides to minimize your travel time in the run-out zone.

Close up of a glide crack on Magnum's South face. This ski track crosses directly over this glide and appears to be from before Jan.24th with 2" of new snow covering it. 

 

Low snow coverage

Below 2000’ low snow coverage is deceiving with only a few inches of new snow covering rocks, ice and vegetation. Take your time getting in and out of the alpine today.


Mountain Weather

Yesterday skies were sunny and clear with light variable winds averaging 5-10mph. No new precipitation was recorded and temperatures increased slightly from single digits into the mid teens to low 20’sF during the day.  

Overnight ridgetop winds have increased, averaging 15mph with gusts into the low 30’s. Wind directions are variable based on location. As of this morning Sunburst wind direction is Easterly, and Seattle Ridge has more of a Southwesterly flow. Temperatures have remained in the teens (F) overnight and no precipitation has been recorded.

Today ridgetop winds are expected to remain moderate, averaging 15mph with gusts into the high 20’s to low 30’s from the Northeast. Temps will be in the low to mid 20’s F, with partly cloudy skies.

Tonight there is a chance for light precipitation, up to an 2” of new snow at higher elevations and 1” at sea level. Temperatures are expected to remain in the low to mid 20’s F and winds will remain moderate 15-25mph, mostly from the Northeast into the evening. 



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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 19  31 
Summit Lake (1400') 13 
Alyeska Mid (1700') 16   0 22 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 16  25 
Seattle Ridge(2400') 17  Var  33 

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 16, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedThanks all for a safe and fun season on the Chugach NF! Stay tuned for the 2017/18 season. #playsafe #snowtosealevel
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail will be open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
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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