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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Thursday, February 4th 2016
Created: Feb 4th 6:39 am
4 High Alpine / Above 2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
3 Considerable Treeline / 1,000'-2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
2 Moderate Below Treeline / Below 1,000' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
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The Bottom Line

Today the avalanche danger is HIGH in the Alpine (above 2500') where natural avalanche activity is likely due to high winds and heavy precipitation.  A CONSIDERABLE danger exists at Treeline where natural glides avalanche and wind slabs +3’ thick are possible and could easily entrain wet snow below 1500’. Below treeline (1000') a MODERATE danger exists where an avalanche in steep channeled terrain could run into this elevation band.

South of Turnagian Pass, including Johnson Pass and Lynx Creek, a variety of weak layers persist within the snowpack. Today strong winds and precipitation will be adding stress to the snowpack and warrants extra caution in these areas. Click HERE for details about a large avalanche triggered in Groundhog Creek on Saturday in Lynx Creek area and for recent observations from Summit Lake click HERE

 


Primary Concern

Today is day two of a warm and wet storm that has dumped 1.5” of water (15-20” of new snow) in the upper elevations of Turnagain Pass. Rain was observed to 1000’ yesterday, but with rising temperatures rain will easily reach 1500’ today and maybe higher. Strong Easterly winds and another 12” of new snow (.9” of water) is expected today and will be adding stress to a variety of avalanche problems.   

Wind SlabsStormy conditions continue to make wind slabs our primary concern for the upper elevations. Triggering a wind slab +3’ thick is likely on wind loaded and cross loaded features. Below 3000’ these wind slabs are sitting on an old snow/crust combo and may propagate further than expected. Until more information is known about how this new snow is bonding to this interface give large open slopes like Magnum’s West face and the East Face of Seattle Ridge extra space today. 

Wet Snow: Wet snow is sitting on a slick crust in the mid elevation band. Rain to 1500’ will be lubricating this poor interface making wet avalanches possible in the mid elevation band. This hazard will be especially dangerous under big open slopes and in terrain traps like gullies or abrupt transitions where an avalanche from above could have high consequences. Keep slope angles under 35° and pay close attention to your runout zones. Natural activity is possible in steep channeled terrain and will likely entrain wet snow.

Cornices: Cornices will be unstable today and may release naturally. These features have been tender over the last week and now have the added stress of high winds and new snow. These backcountry bombs can easily trigger a a wind slab below and should be avoided.     

 

Below 3000' a stout crust + old snow combo is sitting under under 2' of storm snow. Click HERE for an observation from yesterday. 

 


Secondary Concern

Warm temps, rain and wet snow continue to add weight and stress to glide cracks throughout Turnagain Pass. These unpredictable hazards are widespread in steep terrain between 1000’ to 2500’ and can release without warning. Today’s limited visibility will make it challenging to identify existing glides, and is an added reason to avoid being on or under steep terrain. 


Mountain Weather

Since yesterday 1.2” of water has been recorded; 14” of new snow at the Center Ridge weather station. Northeast ridgetop winds have averaged in the 30’s with gusts in the 50’s.  Temperatures have been on the rise pushing rain as high as 1500’ early this morning.  Yesterday rain/snow line hovered around ~1000’ most of the day.

Today another 0.9” of water is expected to fall, another 12” in the alpine. Temperatures will remain warm with rain below 1500’.  Easterly ridgetop winds will remain moderate to strong throughout the afternoon.

Tonight temps look to be cooling slightly bringing rain/snow line back down to ~1000’. Easterly winds and precipitation will be decreasing this evening, but scattered showers are expected into tomorrow. 

 



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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 31  14   1.2 106 
Summit Lake (1400') 33  .1  29 
Alyeska Mid (1700') 33  1.06  75 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 24  ENE  31   64
Seattle Ridge(2400') 26 

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: Mar 15, 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: Open
Skookum Drainage: OpenSkookum drainage closes to motorized use on April 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: Open
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
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