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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Aleph Johnston-Bloom  
Tuesday, March 14th 2017
Created: Mar 14th 5:29 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.
 Show the Complete North American Avalanche Danger Scale
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. 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.

 


Primary Concern

The weather DJ seems to have left the buliding and the weather pattern continues to be stuck on repeat. Sunshine, sunshine, sunshine... Yesterday cloudy skies in the middle of the day were almost a tease. Today there will be an uptick in afternoon NW winds to add a little spice but really the story remains the same. We have seen 20 days without any precipitation and nine days since a wind event impacted our region. Despite the weather and snowpack conditions being mostly stable and the weak layers dormant, a hard wind slab 12-18” deep was triggered by a snowmachiner three 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 SlabsOld 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 start to pick up any soft snow. There is not much left to transport. Watch for shooting cracks if slopes are actively being loaded.

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.

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

Persistent Slabs and Deep SlabsThere 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). 

This hard wind slab was initiated by a snowmachine just below the trees, lookers left side of photo, while exiting the slide path. This was on a SE aspect of Seattle Ridge at 2400' in an area near 'God's Country'. Photo by Brian Bird.

 High clouds over Seattle Ridge yesterday. Note the series of glide cracks along the ridge that continue to open.


Mountain Weather

Yesterday high clouds rolled into the region as a short wave passed over. Skies cleared in the evening. Winds were light and variable. Temperatures were in the teens to low 20Fs. Overnight the temperatures dropped into the single digits. 

Today is forecasted to be clear, sunny and cold. Valley temperatures may hit the low 20s but the ridge tops will remain in the single digits to low teens. NW winds are expected to pick up with gusts into the 20s. Tonight temperatures may drop below 0F. 

Tomorrow will be partly to mostly cloudy with a chance of light snow in the afternoon and the colder temperatures will continue. There is hope that the overall pattern will change more significantly early next week. 

*Seattle Weather Station tables and graphs are not recording temperature history. The current temperature at 7 am was 7F. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 11  59 
Summit Lake (1400') 28 
Alyeska Mid (1700') 14 0 56 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  8 variable   3  9
Seattle Ridge(2400')  *n/a variable   4   12

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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