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Avalanche Advisory

Turnagain Area Avalanche Advisory
Tuesday, January 1st 2019 7:00 am by Wendy Wagner
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

Hurricane force wind plus another foot of new snow overnight has brought the avalanche danger to HIGH in the Alpine. Natural storm snow avalanches 2-4' thick are likely while this second storm hits. The avalanche danger is CONSIDERABLE in the treeline and below treeline band where natural storm snow avalanches may occur and human triggered avalanches are likely. Wet snow avalanches below 1,000' are possible with forecast rising temperatures. 

Travel is NOT recommended in the Alpine, above the trees, or in runout zones at all elevations. Cautious route-finding and conservative decision-making are essential if choosing to travel in the trees. 

GIRDWOOD: Roof avalanches are expected with warming temperatures. Pay attention to children and pets and where you park your car. 

SUMMIT LAKE / JOHNSON PASS / LYNX DRAINAGE:  South of Turnagain Pass, keep in mind old buried weak layers exist and there is a potential for very large avalanches to occur that break near the ground. 


 Show the Complete North American Avalanche Danger Scale
4 High Alpine / Above 2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
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
  • Parking may be difficult along Turnagain Pass. Please be aware of parking safely and avoid blocking unplowed lots as DOT crews work to clear roads and parking areas.

Avalanche Problem 1

Storm Slabs

Almost Certain
Very Likely
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Unlikely

Chance

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Size

The second storm, in a two-part series, is over the region now and bringing in the 2019 New Year with a bang. The highest wind gust recorded this season occurred at 0200 this morning at the Sunburst weather station - 113mph from the NE. Not to mention an hourly average of 76mph... This second system is a bit more blow than snow. Overnight, roughly a foot of new snow has fallen at the upper elevations with 2-5" forecast for today. It is the winds that are expected to create much of the havoc and induce avalanche activity, which will be in the form of cornice falls, wind slabs, storm slabs and loose snow avalanches. 

Skies opened yesterday and small pockets of storm slabs were seen and reported from the first storm. The good news was all avalanche activity we know of was confined to the storm snow and did not show wide propagation. However, there are still many areas we have no information for, such as upper Girdwood Valley, Johnson Pass, Lynx Crk and Summit Lake. 

The other issue is a layer of buried surface hoar (buried by the first storm beginning 12/30) that now sits 2-3' deep. Observations yesterday pointed to little reactivity in the layer as it was sandwiched between very loose soft snow. Settlement and wind effect can quickly turn loose snow into a slab and avalanche potential rises quickly. 

If you're headed into the trees look for signs of collapsing/cracking and recent avalanches breaking deeper than you may expect. If avalanches begin to break in the buried surface hoar they will be unmanageable. Watch for any area with stiffer snow over softer snow and stay well clear of runout paths from terrain above you.

 New Year Storm Cycle - total snowfall at mid-elevations from Sunday to 6am Tuesday: 

  • Turnagain Pass SNOTEL: 23" 
  • Girdwood – Alyeska Midway: 25” 
  • Summit Lake: 7-12" 

SNOW IMMERSION SUFFOCATION:  Getting caught in a tree well, stuck head down in a depression and other means of snow immersion are all possible with so much snow. Watch your partners and be aware of this hazard! 

 

Natural storm slab avalanche from Sunday night below Hippy Bowl on Tincan's SW face. (Photo: Nikki Champion)

 

Small natural storm slab avalanche in the Tincan Trees from Sunday night. (Photo: Nikki Champion)


Avalanche Problem 2

Glide Avalanches

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Chance

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Under all this new snow are hidden glide cracks. They are looming over popular ski and snowmachine terrain. Today isn't the day to be in the runnout of these anyhow but when skies clear and the storm snow issues settle down, don't forget to watch for brown cracks and limit as much time under them as possible. They can release at anytime and have already done so in high use areas of Corn Biscuit and Lipps. 


Additional Concern

Persistent Slabs

South of Turnagain:  A shallow and poor snowpack structure exists in the Summit Lake zone. Buried weak layers of facets associated with crusts sit near the base of the snowpack. Although Summit did not get as much precipitation with these storms it will be important not to forget the possibility of triggering a larger avalanche that could release near the ground. Check out the Summit observations HERE for the most current information. 


Mountain Weather

Yesterday:  Partly cloudy skies with good visibility. Winds died down into the teens across the region before picking back up in the evening as the next storm moved in. Ridgetop winds have been averaging 25-75mph with gusts over 100mph. The rain/snow line has been near 500'. Temperatures remain near 32F at 1,000' and in the 20'sF along the ridgetops. 

24-hour precipitation and wind: 

  • Turnagain Pass SNOTEL: 8" (0.9" SWE), Sunburst wx station winds: NE, 40-76 mph, gusting to 113
  • Girdwood – Alyeska Midway: 5” (0.6” SWE), Max's wx station winds: E-NE 25-35 mph, gusting to 76
  • Summit Lake: 4-6" (0.3” SWE)

Today:  Light snowfall should continue today adding another 2-5" as the brunt of the storm has passed. Temperatures should rise to the mid-30'sF at 1,000' bringing the snow line up to 1,000' (possibly 1,500' in places). Ridgetop winds should start a slow decline into the 20-40mph range from the east - which is still very strong however. Tonight we could see another inch or so of snow as the storm heads out for good.

Tomorrow:  A cooling and drying trend is on tap for Wednesday and the latter part of the week as a ridge of high-pressure builds over the region.


*Seattle Ridge weather station was heavily rimed and the anemometer (wind sensor) was destroyed.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 30  0.9  69 
Summit Lake (1400') 32  0.3  18 (estimate) 
Alyeska Mid (1700') 31  0.6  53 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 23  ENE  41  113 
Seattle Ridge(2400') 28  *N/A   *N/A *N/A 

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: May 06, 2019 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed as of 4.3.19
Placer River: ClosedClosed as of 3.20.19 due to lack of snow.
Skookum Drainage: ClosedPlacer access closed as of 3.20.19 due to lack of snow.
Turnagain Pass: ClosedClosed as of 5/6. Thanks for a great season all, see you next winter!
Twentymile: ClosedClosed as of 3.20.19 due to lack of snow.
Seward District
Carter Lake: Closed
Lost Lake Trail: ClosedClosed as of 3.22.19 due to lack of snow
Primrose Trail: ClosedClosed as of 4.3.19 due to lack of snow
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: ClosedClose as of 5.1.2019
South Fork Snow River Corridor: ClosedClosed as of 3.20.19 due to lack of snow.
Summit Lake: Closed

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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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