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Avalanche Advisory

Turnagain Area Avalanche Advisory
Thursday, April 12th 2018 4:56 am by Aleph Johnston-Bloom
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

Sunshine, warm temperatures, fresh snow and rain saturated snow will keep the danger at CONSIDERABLE today. Human triggered wet snow avalanches and storm slabs are likely and naturals are possible, especially this afternoon. In the Alpine triggering a persistent slab avalanche 1-2' thick remains possible on Northerly aspects where drier snow exists. Give cornices a wide berth.


 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.
3 Considerable Treeline / 1,000'-2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
3 Considerable Below Treeline / Below 1,000' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
Avalanche Problem 1

Wet Loose

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Yesterday as the sun poked out late in the afternoon a wet loose avalanche on Raggedtop mountain in Girdwood triggered a wet slab. Observers also noted new wet loose snow avalanches around the region. Rain/snow line was approximately 2700'. Conditions below that were described as "slop" in the saturated surface snow and above that new snow easily formed roller balls. A few skiers remarked on the "parade of pinwheels" initiating from their turns. There was clearing last night and a crust formed on the surface of the snowpack. This will slow snowpack warming down in the morning. However, the temperatures are forecast to rapidly rise and it is supposed to be clear and sunny with calm winds. Expect human triggered wet loose avalanches to become likely on solar aspects and watch for naturals later in the day. The wet loose avalanches may trigger wet slabs. If you do decide to recreate today pay attention to the depth you are sinking in and get off the slope if the snow is over your boot tops or your machine is trenching in. Watch for roller balls.  Expect loose snow moving to entrain more as moves downhill. Any fresh snow in the Alpine may be especially reactive on solar aspects. If the clouds move in early and trap the heat, fresh snow on shaded aspects may also become more reactive. Wet loose and wet slab avalanches today could be large and dangerous.

Wet slab avalanche on Raggedtop triggered by loose snow off of the rocks. 

Wet loose avalanches on Raggedtop initiated when the sun came out. 


Avalanche Problem 2

Storm Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Storm slabs: The precipitation over the past few days in the Alpine has fallen as snow. This rain/snowline has fluctuated so pay attention to changing conditions. Locations closer to the coast may have received up to a foot above 3000'. This storm slab may be especially reactive as temperatures rise today and on solar aspects as the sun hits. The winds have been strong as well and this may have created deeper slabs on leeward aspects. Look for wind drifts or pillowed snow, watch for cracking and remember conditions could change rapidly as the sun warms the snow. 

Cornices: This new snow and wind will have also added to already large cornices.  It's that time of year where the snowpack is warming up and cornices will begin to break. Give cornices a wide berth.


Additional Concern

Persistent Slabs

In the Alpine on Northerly shaded aspects above the rain/snow line triggering a slab avalanche 1-2' thick on weak faceted snow is still possible. The old slab/facet combo remains suspect and may be more tender with the additional snow and wind loading. 

 


Mountain Weather

Yesterday was mostly cloudy with rain and snow showers on and off throughout the day. Skies became broken in the late afternoon and eventually cleared overnight. Temperatures were in the high 20Fs to mid 40Fs depending on elevation. The rain/snow line was around 2700'. Winds were easterly 15-25 mph with gusts into the 50s. Overnight temperatures dropped into the mid to low 30Fs and winds became light. 

Today is forecast to be mostly sunny and could be the warmest day of the season so far with highs getting close to 50F. Winds will be light and easterly. Tonight will be partly to mostly cloudy with temperatures dropping into the low 30Fs. Winds will become calm. 

Tomorrow is forecast to be partly to mostly cloudy with temperatures in the high 40Fs again. Temperatures may drop below freezing overnight Friday and skies are forecast to clear for the weekend. There is a chance of rain/snow early next week as another low tracks into the Northern Gulf. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 36   0  0.2  71

Summit Lake (1400')

 38  

  0  0.1  26
Alyeska Mid (1700')  36     0  0.4  68

 RIDGETOP 24-hour data (6am - 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  27  ENE  19  59
Seattle Ridge(2400')  32  ESE    20   52

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
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