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Avalanche Advisory

Turnagain Area Avalanche Advisory
Wednesday, December 19th 2018 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 1,000'. Wind slabs will be possible to trigger on steep wind-loaded slopes. Watch for storm slabs forming and pay attention to changing conditions. Additional concerns: watch your sluff in steep terrain and avoid traveling underneath glide cracks.

JOHNSON PASS AND LYNX CREEK: We have no snowpack data from these areas. The snowpack can sometimes be similar to Summit Lake; where we continue to find poor snowpack structure and more reactive weak layers. Ease into avalanche terrain and look for signs of instability. 

SUMMIT LAKE:  There are more developed weak layers near the ground that continue to be reactive in stability tests. There is an increased chance a person could trigger a larger slab avalanche. Choose terrain carefully.

LOST LAKE: This zone is out of our advisory area and we have no snowpack information from here. Please let us know what you see! Ease into avalanche terrain 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

Many riding areas on the Chugach National Forest opened yesterday. Please check the riding area status below for the most up-to-date information. The avalanche center would love to know what you are seeing out riding. See any recent avalanches, shooting cracks or experience the snowpack collapsing??? Please send us an observation or tag us in a photo @chugachavy. Remember to always carry avalanche rescue gear and use stafe travel protocols: ride one at a time in avalanche terrain, park out of runout zones and avoid terrain traps. 


Avalanche Problem 1

Wind Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

There is a lot of snow available for transport and the winds bumped up early this morning, blowing from the east 20 mph gusting into the 40s on Sunburst. Maxs Mountain weather station saw gusts into the 50s.  Look for tender wind slabs along ridgelines, especially on unsupported slopes. Girdwood Valley picked up another 5" of snow in the last 24 hrs and Turnagain Pass an additional 3". Since the storm on Sunday avalanche activity has been relegated to small pockets of storm slab, soft wind slab and loose snow sluffs. Today it will be important to watch for stiffer snow over softer snow, cracking and whumpfing (collapsing). Due to more snow in the Girdwood Valley wind slabs could be thicker. As always think about the consequences of even a small slab in steep terrain. As more snow falls today storm slabs may form quickly and be reactive. 

Loose snow avalanches: In areas protected from the winds watch your sluff. Sluffs could start getting larger with the cooler temperatures and the quantity of soft snow. 

Sunburst weather station's bump in winds this morning. 12-19-18

Remember there is a lot of snow available for transport! New snow that fell Sunday in Girdwood. 12-16-18. Photo: Andy Moderow

 

 

 


Avalanche Problem 2

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

As we have been mentioning for a while now, in thinner snowpack zones such as Summit Lake and Crow Pass, we are tracking buried layers of facets, crusts and buried surface hoar that sit 1-3' under the snow surface. These layers are most prevalent in the mid-elevations (2000’ – 2700’). A lack of avalanche activity has been pointing to an unlikely chance for an avalanche releasing in these deeper layers. However, Summit Lake has poor snowpack structure and stability tests still show the potential for an avalanche to release. Wind loading this morning will potentially stress these weak layers in upper elevation start zones.  As we push out into more and more terrain in areas that may have a thinner snowpack like Lynx Creek and Johnson Pass, we need to keep in mind the buried weak layers.  

Fresno snow pit with weak snow near the ground, 12-18-18


Additional Concern

Glide Avalanches

We have had several reports that the glide cracks are opening. Glide cracks we know about are on Sunburst's SW face under the weather stationSW face of Tincan Proper, Gold Pan area (behind Cornbiscuit/Magnum) and a crack that did release in the Johnson Pass area. These cracks can release at any moment. They are not associated with human triggers and the best way to manage the hazard is to avoid being on or beneath slopes with cracks. 


Mountain Weather

Yesterday: Sky cover fluctuated between overcast and obscure. Light snow fell on and off throughout the day. Winds were light and easterly and temperatures were in the teens and 20Fs. Overnight snow showers continued. Temperatures stayed in the teens and 20Fs and winds were calm.

Today: At 4 am this morning easterly winds picked up blowing 20 mph and gusting as high as 56 mph on Maxs Mountain weather station. Today winds are forecast to be 10-20 mph with gusts into the 40s. Temperatures will be in the 20Fs and light snow is forecast to continue falling, 1-6".  Winds decrease overnight and temperatures will be in the teens with clouds clearing out.  

Tomorrow: Thursday is forecast to be mostly sunny. Temperatures will be in the teens and winds will be light. Overnight temperatures will drop into the single digits. This cold and clear pattern looks to last into Saturday. Stay tuned for next low moving into the Gulf Saturday night. 


*Seattle Ridge anemometer (wind sensor) is rimed over and not reporting. Temperature data went down at 1:00 pm yesterday. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 20   0.2  39  
Summit Lake (1400') 20    1  0.1  14  
Alyeska Mid (1700')

20  

 5  0.4  31 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 17  NE   3  45
Seattle Ridge(2400') *18  *no data  *no data    *no data 

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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