Avalanche Advisory

Turnagain Area Avalanche Advisory
Wednesday, March 15th 2017 7:00 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

LOW avalanche danger remains in the backcountry at all elevations. Although triggering an avalanche is unlikely, it is not impossible on steep wind loaded features and in extreme terrain. Pay attention to any recent wind loading and be aware of old hard wind slabs and loose dry avalanches(sluffs) in steep terrain, as well as large cornices. Glide cracks continue to open - limiting exposure under these is recommended.

Good travel habits are important, even during 'green light conditions'. These include exposing only one person at a time on a slope, watching your partners closely and having 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.

 Show the Complete North American Avalanche Danger Scale
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.
Avalanche Problem 1

Northwest winds picked up in the afternoon gusting into the 40s on Seattle Ridge. Overall there is really not much soft snow to blow around. There was some flagging was observed as the settled surface snow (near surface facets) was blown into the atmosphere. If traveling in the Alpine today be on the lookout for freshly pillowed snow and watch for cracking. If there is any fresh wind slab it will be shallow, small pockets. We have seen 21 days without any precipitation and are hoping for a trace of snow today and looking forward to a shift in the overall pattern this weekend. Despite the snowpack conditions being mostly stable and the weak layers dormant, a hard wind slab 12-18” deep was triggered by a snowmachiner four days ago on a SE aspect of Seattle Ridge. This is a good example of a wind loaded terrain feature still harboring unstable snow and a good reminder that LOW danger does not mean NO danger. Kicking off even a small wind slab or loose snow avalanche in steep terrain may have high consequences. Things to keep in mind if you are headed to the mountains today:

Wind Slabs: Old and hard winds slabs are easy to find but for the most part they are locked into place. Smooth pillowed snow on steep unsupported features or in rocky areas will be the most suspect zones for someone to initiate an old wind slab. Pay attention to blowing snow today if the NW winds continue and pick up any soft snow.  Watch for shooting cracks indicating recently loaded slopes.

Loose Snow Avalanches (Sluffs): Dry sluffs on steep slopes are probable and have been fast moving this week.

Glide Avalanches: Glide cracks continue to slowly open above popular terrain on Seattle Ridge and in other areas of the advisory area. These could release at any time, watch for these cracks and avoid being under them.

Cornices: Cornices should always be given a wide berth from above and limit exposure time traveling underneath.

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. These weak layers with varying degrees of strength are in a dormant stage due to plenty of time to adjust with a lack of changing weather. Although its unlikely, an avalanche breaking deeper in the pack isn't completely out of the question in Johnson Pass, Lynx Creek and in parts of Girdwood Valley (especially around Crow Pass). 

Snowmachine triggered wind slab avalanche on Seattle Ridge on Saturday. This is terrain is the aspect that loads with NW winds. Look for signs of recent loading today. 


Mountain Weather

Yesterday was mostly clear and sunny with some high clouds moving in during late afternoon. Temperatures were in the single digits in the alpine and got into the low 20Fs in valley bottoms. NW winds picked up in the afternoon and gusted into the 40s in the evening. Temperatures stayed in the single digits at upper elevations and dropped below 0F in some valley locations overnight.

The diurnal fluctuation is forecasted to continue today with temperatures again rising in the afternoon to the low 20Fs at low to mid elevations and teens at ridge tops and dropping again at night. The skies will be partly to mostly cloudy. There is a slight chance of trace of snow falling today. Winds will continue from the NW gusting into the 20s, potentially increasing in the afternoon. 

Tomorrow will be mostly sunny again with similar temperatures and NW winds. From the National Weather Service regarding the weather pattern shift this weekend, "The trajectory of the low moving through the gulf, and associated impulses producing precipitation, are difficult to pinpoint and will be watched closely during the next few days." Time for snow dances? Praying? What will make it snow? Stay tuned! 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 10   0 59
Summit Lake (1400')  8  0  0 28 
Alyeska Mid (1700')  12  0  0 56 


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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  7 20 
Seattle Ridge(2400') 6  NW  15 42 

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: Oct 05, 2019 )

Glacier District
Johnson Pass: ClosedClosed
Placer River: ClosedClosed
Skookum Drainage: ClosedClosed
Turnagain Pass: ClosedClosed
Twentymile: ClosedClosed
Seward District
Carter Lake: ClosedClosed
Lost Lake Trail: ClosedClosed
Primrose Trail: ClosedClosed
Resurrection Pass Trail: ClosedClosed. Will be open for the 2019/20 season pending adequate snow cover.
Snug Harbor: ClosedClosed
South Fork Snow River Corridor: ClosedClosed
Summit Lake: ClosedClosed

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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.

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