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Avalanche Advisory

Turnagain Area Avalanche Advisory
Wednesday, April 11th 2018 4:53 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

Above freezing temperatures and rain showers will keep the danger at CONSIDERABLE today. 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
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
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Possible
Unlikely

Chance

Historic
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Yesterday saw heavier rain in the early morning then rain showers on and off throughout the day. Portage picked up over an inch of rain. Temperatures were above freezing to around 3500'. Observers reported snow becoming progressively more saturated especially below 2000'. Skies cleared briefly last night and there was a superficial freeze. However, today a bit more rain is in the forecast, we may see some afternoon clearing with direct sun and the temperatures remain warm. All these factors are continuing to make triggering a wet loose avalanche likely and naturals remain possible. There were a number of natural wet loose avalanches observed yesterday with the largest occurring on the west face of Pyramid mid morning. The snowpack could 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. 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 sun comes out today. 

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. 

Natural wet loose avalanche on Pyramid

Wet loose avalanches on Magnum


Avalanche Problem 2

Persistent Slabs

Almost Certain
Very Likely
Likely
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Unlikely

Chance

Historic
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Above the rain line triggering a slab avalanche 1-2' thick on Northerly 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 with the additional few inches of heavy snow from yesterday. Wind loading may also add stress, as the ridgetop winds remained strong yesterday and continue today. 


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 partly to mostly cloudy with heavier rain falling in the early morning and localized rain showers on and off throughout the day. Over an inch of rain fell in Portage Valley. Temperatures were in the 30Fs to 40Fs. Winds were Easterly 15-25 mph with gusts into the 40s. Overnight there was brief period of clearing. Temperatures remained above freezing to around 3500'. Sunburst (3812') hit 32F this morning at 5 am. Easterly winds decreased overnight and are picking up again this morning. 

Today is forecast to be mostly to partly cloudy with rain showers. Winds will be easterly 15-25 mph with gusts into the 40s. Temperatures will be in the 30Fs and 40Fs. Tonight temperatures will cool down a bit as colder air moves into the region. 

The weather for the next couple of day looks to be a mix of sun and clouds, rain and snow showers and variable temperatures. If the cooler air lines up with some clearer skies at night we could get more of a freeze. Sunshine is in the forecast for the weekend.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880')  38  0 0.2 73 
Summit Lake (1400')  36   0   0.1  28  
Alyeska Mid (1700')  37  0  0.1  69  

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  28  ENE  20 45 
Seattle Ridge(2400')  33  ESE  13  27  

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 20, 2018 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed as of April 20
Placer River: ClosedClosed as of April 17th
Skookum Drainage: ClosedClosed as of April 1st.
Turnagain Pass: Open
Twentymile: ClosedClosed as of April 13th
Seward District
Carter Lake: Open
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: Open
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
If you have comments or questions regarding CNFAIC operations or winter recreation management, please email staff@chugachavalanche.org
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