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Avalanche Advisory

Turnagain Area Avalanche Advisory
Monday, February 11th 2019 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

The avalanche danger is MODERATE above 2000'. Look for signs of recent wind loading. Triggering a small wind slab will be possible on steep, leeward terrain features. There is also still a chance of triggering a large slab avalanche 2-3’ thick on slopes 35 degrees and steeper. Give cornices a wide berth, avoid travel under glide cracks and watch for sluffing.

SUMMIT LAKE / JOHNSON PASS: Areas south of Turnagain Pass harbor a thinner, weaker snowpack with multiple weak layers present including the MLK buried surface hoar. Choose terrain wisely and look for signs of instability. 

 


 Show the Complete North American Avalanche Danger Scale
2 Moderate Alpine / Above 2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
2 Moderate Treeline / 1,000'-2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Special Announcement

Saturday, February 2nd a snowshoer triggered an avalanche and was caught, carried and suffered a minor head injury on the Harding Icefield trail. For more details read the accident report HERE.  We really appreciate the individual involved sharing their story. This is a good reminder that summer trails often travel through avalanche terrain in the winter. 


Avalanche Problem 1

Wind Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Yesterday for most of the day the region saw sustained northeasterly winds 10-20 mph. Sunburst weather station recorded gusts into the 30s and 40s. Although only a trace of new snow fell there was old soft snow available for transport. Look for signs of wind loading in the Alpine. Fresh wind slabs maybe tender on steep, unsupported, leeward slopes. Watch for cracking in the surface snow and stiffer snow over softer snow. Although wind slabs are likely to be shallow, they could be more dangerous if they were to step-down and trigger a large slab that breaks in the MLK buried surface hoar. On steep, protected slopes watch for sluffing. 

CORNICES: Cornices are looming large in some of the Alpine terrain. Give them an extra wide berth as they often break farther back than expected.

Note the increased wind speeds during the day on Sunburst yesterday. This was enough to move snow in the Alpine.

 


Avalanche Problem 2

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

As time goes on the likelihood of triggering a large avalanche on the MLK buried surface hoar has decreased. Over the last few days many people have been pushing into steeper terrain without incident. However, don’t forget the lingering concern that this is the kind of avalanche problem where several tracks may be on a slope before someone finds a trigger point and the whole slope avalanches. The MLK buried surface hoar that is roughly 1-3' deep has been responsible for 13 human triggered avalanches since January 26th. The last one was Wednesday February 6th on Eddies. On that day snowpack tests were pointing toward a stabilizing weak layer and then the 2'-3' deep avalanche was triggered remotely from the ridge on a steep, unsupported slope. 

What to keep in mind today:

1- This weak layer is widespread in the region and seems to be particularly suspect between 2000'-2500' due to a melt-freeze crust associated with it. 
2- Use safe travel protocol. Expose only one person at a time (this includes paying attention to other groups in the area), watch partners, stop in safe zones and be rescue ready.
3- Wind loaded steep features, large connected and unsupported slopes are the most suspect. As always, one can simply avoid high consequence terrain and stick to slopes under 35 degrees with nothing steeper above to avoid the issue. 

The MLK buried surface hoar over a melt-freeze crust in a snow pit on Repeat Offender, 2-7-19. 


Additional Concern

Glide Avalanches

Glide cracks continue to creep open and are scattered across the region. The last glide crack to release into an avalanche was over a week ago in the Summit zone just north of Manitoba. Glide cracks are unpredictable, not associated with human triggers, and can release without warning at any time. Look out for glide cracks and limit exposure under them.

Lipps glide cracks threaten the skin track and ski terrain, 2-8-19.

 


Mountain Weather

Yesterday: Mostly cloudy skies with very light snow flurries. Winds were northeasterly 10-20 mph with gusts into the 40s. Temperatures were in the 20Fs to 30Fs. Overnight temperatures dropped slightly and winds shifted to the west and eased off, averaging 5-10 mph gusting into the teens.

Today:  Partly cloudy skies with some valley fog becoming mostly cloudy tonight. There is a chance of snow showers overnight, 1-3". Winds will be light and westerly and temperatures will be in the 20Fs and 30Fs. 

Tomorrow: Skies are forecast to clear in the early morning and become mostly sunny. Winds will be light and westerly and temperatures will be in the 20Fs to low 30Fs.  There is a slight cooling trend with sunshine on tap for most of the week. The next chance for snow looks to be over the weekend. 


*The Seattle Ridge anemometer (wind sensor) was destroyed. We have a replacement on the way and it should be operational by mid February.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 29  57 
Summit Lake (1400') 25  25 
Alyeska Mid (1700')  28   trace  0.03  50 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  21  NE  10 48 
Seattle Ridge(2400')  26 *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: Mar 22, 2019 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Open
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: Open
Twentymile: ClosedClosed as of 3.20.19 due to lack of snow.
Seward District
Carter Lake: Open
Lost Lake Trail: ClosedClosed as of 3/22. Unfortunately HEAVY rain over the past week has washed much of the snow off the lower stretches of this trail.
Primrose Trail: OpenPlease stay on trail to avoid resource damage through forested areas.
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: Open
South Fork Snow River Corridor: ClosedClosed as of 3.20.19 due to lack of snow.
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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