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Avalanche Advisory

Turnagain Area Avalanche Advisory
Tuesday, April 10th 2018 4:43 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

Warm weather, a second night with no freeze and rain have increased the danger below 2500' to CONSIDERABLE. Human triggered wet snow avalanches are likely and naturals are possible. In the Alpine triggering a 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
2 Moderate Alpine / Above 2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
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

Rain on snow breaks up bonds and adds load to the snowpack. Yesterday saw rain showers throughout today and the precipitation intensity picked up this morning. Rain continuing today combined with another day of warm temperatures and last night being the second night in a row with no freeze below 3000' has increased the likelihood of both wet loose avalanches and wet slab avalanches. The snowpack will continue to get more saturated throughout the day. 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. Expect loose snow moving to entrain more as moves downhill. Yesterday observers reported large roller balls/pinwheels and the size of human triggered loose avalanches increasing later in the day. Anywhere that had softer drier snow becoming wet was the most tender. 

Wet slab avalanches:  We have not seen any wet slab avalanche activity yet, but it's not out of the question that a wet loose slide (or the weight of a skier or snowachiner) could trigger a wet slab today as water penetrates to lower layers. 

Wet loose avalanches on the North Corbiscuit chutes yesterday. 

 Wet loose avalanches on Pete's South. Expect the size of wet loose avalanches to increase today. 

 


Avalanche Problem 2

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Above the rain line triggering a slab avalanche 1-2' thick on North shaded aspects is still possible. Overall we have seen that the snow from last week has been bonding but haven't forgotten that there is a weak layer under the old storm slab.  The slab/facet combo remains suspect and may be more tender in the Alpine today as heavy wet snow falls. Wind loading may also add stress, as the ridgetop winds remain strong.  

Facets found beneath last weeks storm snow in a pit on the North side of Tincan at 3,200'. Photo: Eric Roberts


Additional Concern

Cornice

It's that time of year where the snowpack is warming up and cornices will begin to break. Give cornices a wide berth.


Mountain Weather

Yesterday was mostly cloudy with rain showers throughout the day. Temperatures were in the 40Fs at sea level and the high 20Fs to mid 30Fs at upper elevations. Winds were easterly 20-30 mph gusting as high as 67 on Sunburst. 

Today is forecast to mostly cloudy with around a half an inch of rain expected. Temperatures will remain in the 30Fs and 40Fs. Winds will continue from the east 15-25 mph with gusts into the 40s. Temperatures will stay warm overnight and rain showers will continue. 

The next couple of days look to remain cloudy with a continued chance of rain as another low moves into the Gulf. There is a chance for some clearing this weekend but the long-term forecast discussion keeps temperatures warm and the overall pattern active. Springtime in AK! 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 37  0.4   71
Summit Lake (1400') 39   0    0.4    30
Alyeska Mid (1700')  36    0   0.34   71

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  28 ENE  25  65 
Seattle Ridge(2400')  31  ESE   21  47 

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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