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Avalanche Advisory

Turnagain Area Avalanche Advisory
Tuesday, March 12th 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 remains CONSIDERABLE in the Alpine today. Human triggered slab avalanches 2-3' thick are likely on steep slopes above 2000'. A MODERATE danger exists at Treeline and below where triggering an avalanche is still possible. Pay attention to changing conditions on solar aspects and with warming temperatures in the afternoon. Watch for roller balls and natural wet loose avalanche activity.  Extra caution is advised. Give cornices a wide berth.

SUMMIT LAKE:  This area has a very shallow and weak snowpack. Strong winds combined with a few inches of snow during the weekend storm may have overload buried weak layers and caution is advised if heading to this area. Look for signs of instability. 

LOST LAKE:  Caution is advised in the Seward region. New snow and wind over the weekend have created dangerous avalanche conditions. The potential for large human triggered avalanches remains in this area as well. 


 Show the Complete North American Avalanche Danger Scale
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
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.
2 Moderate Below Treeline / Below 1,000' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Today will be the first day after this weekend's storm with a real chance of mostly clear skies and sunshine for a least part of the day. Yesterday the area received a couple inches of snow with rain below 1000'. Overnight skies cleared and temperatures dropped below freezing. On lower elevation terrain there will be a crust this morning on the surface. Due to the wet snow yesterday this may extend as high as approximately 2000'. Where this is crust supportable there is a lower likelihood of triggering an avalanche in the layers below. If you or your machine penetrate through crust or your traveling at an elevation that is crust free you need to consider the possibility of triggering an avalanche 2-3' deep on a layer of buried facets/surface hoar. Overall the snowpack is fairly untested and good visibility may lure folks out on to bigger terrain. Slope angle and consequences of a large slide must still be taken into consideration. This type of set-up may not fail with the first skier or snowmachine on the slope. Snowpack tests still show the potential for triggering. As temperatures warm and the sun shines on steep slopes this may increase stress in the slab and make triggering more likely. Additionally look for loading patterns from the strong winds over the weekend. Wind loaded slopes could have deeper slabs and be more prone to triggering on steep unsupported slopes. Use safe travel protocols and ease into terrain. Pay close attention to changing conditions. Look for signs of instability. 

Slab over facets on Tincan, 2100'. 3-10-19. 

 Small skier triggered slab on Tincan, 3-11-19. Photo: Kyle Van Peursem


Avalanche Problem 2

Wet Loose

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Direct sunshine today and warm temperatures in the afternoon may heat up the surface snow and initiate roller balls and progress to wet loose avalanches. Steep, rocky solar aspects will be the most suspect. There is the potential for these loose snow avalanches to trigger slab avalanches on the slopes below if the heating is sustained long enough. If you see roller ball activity starting avoid solar aspects and watch the terrain above you. 


Additional Concern

Cornice

Cornices grew larger during the storm this weekend. Be careful to avoid traveling to close to the edge. Remember cornices often break farther back than expected and could trigger a large avalanche on the slope below. 


Mountain Weather

Yesterday: Mostly cloudy skies with rain/snow showers and rain/snow line fluctuating around 1000'. Temperatures were in the mid 20Fs to high 30Fs. Winds were mostly light and easterly shifting to the west in the evening. Overnight skies cleared and temperatures dropped ranging from just below freezing at sea level to the teens at upper elevations. Winds remained light. 

Today: Mostly clear and sunny in the morning with clouds building later in the day and a chance of snow showers in the evening. Temperatures will be in the 20Fs to mid 30Fs. Winds will be easterly 5-15 mph with gusts into the 20s.  Tonight will be mostly cloudy with temperatures in the 20Fs. Easterly winds will increase with gusts into the 30Fs. Snow showers overnight with 1-5" forecast. 

Tomorrow: Mostly cloudy skies with snow showers throughout the day and snow likely in the evening. Temperatures will be in the 20Fs and 30Fs. Easterly winds blowing 10-20 mph with gusts into the 30s increasing overnight. The position of the low in the Gulf with this system is a still a little uncertain and could impact how much precipitation the area receives. The most intense part of this storm still looks to be Wednesday night. 

*Seattle Ridge wind sensor is not reporting. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 30   0 0.1  69 
Summit Lake (1400')  28    0 27 
Alyeska Mid (1700')  31    3 0.26   73  

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  21  NE  5 18 
Seattle Ridge(2400')  27  *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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