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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Graham Predeger  
Thursday, March 16th 2017
Created: Mar 16th 5:59 am
1 Low Alpine / Above 2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
1 Low Treeline / 1,000'-2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
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The Bottom Line

Avalanche danger remains LOW today at all elevations across the advisory area.  Triggering an avalanche is unlikely though still not impossible.  Steep, wind-loaded features do have all the ingredients for an outlier avalanche.  Very steep (extreme) terrain may also produce fast-moving loose dry sluffs.  Cornices and glide cracks also deserve a mention.  If either of these features fail, a large avalanche could be possible. 

Good travel habits are important, even during 'green light conditions'.  Expose only one person at a time in avalanche terrain, watch your partners closely, communicate and have an escape route planned in case the snow moves. 

Summit Lake, South of Johnson Pass and North in parts of the Girdwood Valley (around Crow Pass):  A reminder that the snowpack remains thinner in these areas with a poor structure. There is still a chance for triggering an avalanche deeper in the snowpack in these areas. Read the Saturday Summit Summary HERE.


Primary Concern

What a long strange trip it’s been without any measurable precipitation… 22 days for those that are counting!  Surface conditions are made up primarily of thin crusts, hard wind board on ridges and near surface facets (recycled powder) in favored areas sheltered from the recent winds.  Avalanche concerns to keep in mind today if venturing out:

 Wind Slabs: Some fresher wind slabs likely formed during Tuesday’s wind event and could be tender, though likely small in size.  Watch for shooting cracks indicating recently loaded slopes and fresher wind slabs.  Older, stiffer wind slabs such as the one triggered on Seattle ridge last weekend will be less likely to trigger by a skier or snowmachiner today. Smooth pillowed snow on steep unsupported features or in rocky areas will be the most suspect of areas for someone to initiate an old wind slab.  

Loose Snow Avalanches (Sluffs): Dry sluffs on steep slopes are probable and have been fast moving this week.  Keep terrain choices and potential consequences in mind when managing sluffs.

Glide Avalanches: Glide cracks continue to slowly open above popular terrain on Seattle Ridge and in other zones across the advisory area. These may release at any time.  Minimize exposure time spent under visible cracks.

Cornices: Cornices should always be given an extra wide berth if travelling along a corniced ridge.  Like glide cracks, minimize your exposure time spent under these backcountry bombs. 

Persistent Slabs and Deep Slabs: There are various weak layers in our thin snowpack. Buried surface hoar sits 1-3+' below the surface and faceted snow sits in the mid and base of the pack. Given plenty of time and a lack of changing weather, these weak layers (with varying degrees of strength) are in a ‘dormant stage’.  Although unlikely, an avalanche breaking deeper in the pack isn't completely out of the question in areas such as Johnson Pass, Lynx Creek and in parts of Girdwood Valley (especially around Crow Pass).  A cornice fall or glide crack release could also be a large enough trigger to wake up one of these persistent slabs.  

Wind-buffed Magnum ridge with a sizeable cornice still in-tact over PMS bowl.  photo: Conrad Chapman

Thin sun-crust capping chained Facets at 2,400' yesterday on Magnum.  photo: Conrad Chapman


Mountain Weather

High clouds making for a grey-bird day were a welcome ‘change’ for many a backcountry enthusiasts in south-central Alaska yesterday.  Unfortunately those clouds weren’t of the precip-producing type.  Temps continue to be unseasonably cool with a high topping out in the single digits at 1880’ on Center ridge.  Winds were light to moderate from the NW at ridgetop levels.

High clouds today will give way to mostly sunny skies by this afternoon.  Expect light winds from the NNE today as the worst of the blow appear to be over (at least for now).  Temps will again start out cool but should warm a bit more today to the low 20's F at 1,000'.  No measurable precip is expected.  

Expect mostly clear skies, light winds and cool overnight temps recovering to the 20's F thru the weekend.  We've got some "chances of snow" materializing in the longer term forecast by early next week.  Stay tuned!

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880')  59
Summit Lake (1400')  9 29 
Alyeska Mid (1700')  9  56

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  0 WNW 16 
Seattle Ridge(2400')  3 20 

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
If you have comments or questions regarding CNFAIC operations or winter recreation management, please email staff@chugachavalanche.org
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