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Avalanche Advisory

Turnagain Area Avalanche Advisory
Saturday, March 17th 2018 5:23 am by Heather Thamm
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche danger is CONSIDERABLE on all aspects and elevations, and may increase to HIGH in the afternoon if we see natural avalanches on Southerly aspects. Triggering a slab avalanche 2-4+’ thick is likely on all aspects below 3000’. Above this elevation where slab depths are deeper, the potential for triggering a very deep and dangerous avalanche exists. Be aware of newly formed wind slabs and unstable cornices in the alpine. Pay attention to daily warming and changing snow conditions and if you see natural avalanches avoid all avalanche terrain. Cautious route-finding and conservative decision making are essential. 

Dangerous avalanche conditions also exist in Summit Lake, check out the most recent Summit snowpack and avalanche summary if you are headed South of Turnagian Pass.


 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.
Special Announcement

CNFAIC has issued a Special Avalanche Bulletin for the weekend due to the potential for a skier or rider or snowmachiner triggering a dangerous slab avalanche. Sunny weather today combined with warm temps and a sketchy snowpack is the perfect recipe for dangerous human triggered avalanches. Lots of activity has occured this week region-wide from Lost Lake all the way to Girdwood and even a few reports of natural avalanches in South Fork, Eagle River.  

Roof avalanches are a serious concern today with warm temperatures, particularly around Girdwood where there is still snow on some roof tops. Be mindful of where children and pets are playing, vehicles parked and entrances to buildings in relation to loaded roofs.


Avalanche Problem 1

Deep Persistent Slabs

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Avalanche danger will rise as a superficial melt-freeze crust breaks down with daily warming and radiation from the sun this afternoon. Light rain fell yesterday, and last night was the second night in a row with above freezing temps in the lower elevations.  Large human triggered avalanches and/or natural avalanches have released daily since Monday from Seward all the way to Girdwood. Some of these avalanches have been remotely triggered while others have released after a skier or snowmachiner were well onto a slope. So far we’ve seen one ‘very large’ natural avalanche, where the crown was a mile-wide, on a NE aspect of Skookum Valley near Placer.  Most of these avalanches have occurred below 3000’, releasing on weak faceted snow on a slick crust, 2-4 feet below the surface. Widespread buried surface hoar and facets have been well documented at all elevations and this poor snowpack structure leaves us concerned about the potential of another very large high-consequence avalanche. A lot of uncertainty remains in the Alpine where slab depths are much deeper and triggering an avalanche could be more stubborn. Today as surfaces become moist and crusts start to break down with daily warming, keep your terrain choices mellow. Slope angles steeper than 30 degrees, and smaller unsupported terrain features are all suspect. There is potential to trigger a slab remotely from below a slope or along a ridge. If you’re playing in the flats, be aware of other parties in the area and avoid runout zones. 

Video of this week's avalanche cycle in the Kenai Mountains.  

 

A natural avalanche seen on SE aspect of Seattle Ridge yesterday afternoon. 

 

Large natural avalanche that released on Tuesday afternoon on a NE aspect of Skookum Valley near Placer. 

 


Avalanche Problem 2

Wet Loose

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Wet loose avalanches or roller balls today are indicative of solar radiation and/ or daily warming temperatures affecting change on the snowpack. We have been seeing this throughout the week with unusually warm temperatures. A wet point release could be small to large and has the potential to trigger a much larger, more dangerous slab, particularly on steep southerly aspects. If the sun comes out this afternoon and evening, natural wet loose avalanches are expected. Pay attention to the surface crust as it breaks down and becomes moist. This will be your first clue that the avalanche danger is increasing.

Small wet point release avalanches were seen yesterday below 2000' on all aspects in very steep terrain where light rain was falling to this elevation. Today expect these to be more prominent on Southerly aspects at all elevations. 


Additional Concern

Wind Slabs

Wind Slabs: In the upper elevations Easterly winds 20-45mph yesterday were loading leeward slopes and adding stress to a very stressed out snowpack. Triggering a newly formed wind slab up to a foot deep is likely on leeward features in the upper elevations where dry-loose snow was available for transport. Sun and warm temperatures could make wind slabs easier to trigger. A fresh wind slab could step down to older snow in the snowpack and create a much deeper and more dangerous avalanche. 

Cornice Fall: Cornices have grown significantly since the March 9th storm, an event that arrived with strong winds and dumped 3-4’ of new snow. If the sun appears it will be heating up cornices today and could make them more unstable. Give corniced ridges an extra wide berth and minimize time spent below them. A cornice fall could trigger and propagate an avalanche on a slope below.


Mountain Weather

 Yesterday was overcast with scattered rain showers below 2000’. Only a trace of precipitation was recorded. Daytime temps reached the mid 40F’s near sea level and mid 30F’s in the mid elevations. Temperatures in the alpine were in the upper 20F’s. Temperatures remained at or above freezing for the second night in a row below 1500’.  Easterly ridge top winds 15-45mph gradually decreased in the late afternoon and evening.     

Today expect scattered rain showers in the morning with clearing skies in the afternoon. Clouds will move back into the area this evening. Unusually warm temperatures will continue today with highs in the mid 40F’s at sea level and mid 30F’s in the alpine. Overnight temps will dip into the upper-20F’s to low-30F’s. Winds will be light from the South. 

Temperatures are expected to remain warm through Sunday and into Monday as another front moves through Southcentral, AK. The Southwest direction of this low will likely favor Cook Inlet and the Mat-Su Valley for precipitation, a mix of rain and snow. Cooler temperatures associated with Arctic air moving into our region are in the forecast by mid week.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 35 .1  85 
Summit Lake (1400') 35  32 
Alyeska Mid (1700') 33   .07 79 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 24  ENE  10 50 
Seattle Ridge(2400') 29  ESE  14  44 

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: Dec 01, 2018 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed
Placer River: ClosedClosed
Skookum Drainage: ClosedClosed
Turnagain Pass: ClosedClosed November 21 due to inadequate snow conditions. #hopeforsnow
Twentymile: ClosedClosed
Seward District
Carter Lake: ClosedClosed
Lost Lake Trail: ClosedClosed
Primrose Trail: ClosedClosed
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: ClosedClosed
South Fork Snow River Corridor: ClosedClosed
Summit Lake: ClosedClosed

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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