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Avalanche Advisory

Turnagain Area Avalanche Advisory
Saturday, March 2nd 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

There is a generally LOW avalanche danger in the Turnagain, Girdwood and Portage areas. Triggering a slab avalanche is unlikely. Watch for sluffs on steep shaded slopes and give cornices a wide berth. Glide cracks are moving, minimize travel under them as they can release at anytime.

SUMMIT LAKE / SILVERTIP:  More caution is advised south of Turnagain Pass as the snowpack is thin and harbors old weak layers. There is potential for a person to trigger a slab avalanche on steep slopes. See additional concerns below.

PORTAGE LAKE and BYRON GLACIER TRAIL:  Heads up that thin ice has been reported on Portage Lake. Additionally, the popular snow cave past the end of the Byron Glacier Trail is very dangerous and unstable. If you didn't see this video from February check it out.


 Show the Complete North American Avalanche Danger Scale
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.
Special Announcement
  • Take a minute out of your backcountry day to help the Community Snow Observations crew with gathering snow depth information in Alaska!! Website is communitysnowobs.org. It's easy to do, you just need a smart phone, 30 seconds and your probe to measure the snow depth.
  • Springtime has hit Hatcher Pass as well - check out today's advisory HERE!!

Avalanche Problem 1

After 8 days of brilliant sunny skies and springtime temperatures, a few clouds and cooler air is slated to move in today. The decrease in temperature will limit wet avalanche activity on south facing slopes and avalanche danger has dropped to Normal Caution (LOW danger). Over the past week, avalanche activity has been related to afternoon warming on southerly facing slopes. This triggered a number of wet loose slides, a few moist slabs and a few glide avalanches. As the southerly slopes now sport a solid sun crust, which may not soften today, and wet avalanches are not expected, glide avalanches are the exception moving forward. Things to keep in mind if you are headed out today:

  • Glide avalanches - Several small glide cracks released yesterday. These types of avalanches are highly destructive, unpredictable and not associated with human triggers. It's always best to watch for and limit exposure under glide cracks.
  • Dry-loose sluffs - Loose surface snow exists in steep shaded terrain. Dry sluffs can move faster than expected or knock a person over.
  • Cornice falls - As always in mountain travel, give cornices a wide berth. 
  • An outlier slab avalanche - Although it is unlikely a person could trigger a slab avalanche, the mountains can harbor surprises, especially in thin snowpack areas. Considering the consequences before entering into high consequence terrain and maintaining good travel protocol are good habits that could pay off one day.

 

Glide avalanches on the lower portion of Raggedtop Mtn, releasing yesterday (3/1). Photo taken from Girdwood.

 

Recent wet loose avalanche activity in upper Glacier Creek / Girdwood Valley. 


Additional Concern

Persistent Slabs

South of Turnagain - Summit Lake and Silvertip zones:  For anyone traveling in this area note that a shallow snowpack with a generally poor structure exists. A variety of old weak layers (facets and buried surface hoar) sit in the mid and base of the snowpack. It is uncertain as to how reactive these layers are at this point and if they could produce a slab avalanche. We do know whumpfing has been observed in the Summit area and last Thursday's (2/21) wind event triggered many large slab avalanches breaking in deeper weak layers. Assessing the slab as well as the weak layer will be important. Old wind slabs in steep terrain sitting on weak snow are the most suspect places to trigger an avalanche.


Mountain Weather

Yesterday:  Sunny skies with light and variable winds were over the region. Temperatures climbed into the mid 30'sF along the high peaks and mid elevations, while valley bottoms reached 30F. Overnight, temperatures have only dropped to the teens at most low elevations while ridgetop temperatures have dropped to the teens as well - limiting the inversion.

Today:  A few clouds are slated to move in today along with a chance for valley fog. The ridge of high pressure is weaker and that has decreased temperatures in the Alpine and increased them at sea level. Daytime highs should reach the mid 20'sF along ridgelines and the mid 30'sF in the low elevations. Ridgetop winds will be light from the east, 5-10mph. 

Tomorrow:  Mostly cloudy skies with a chance for a snow flurry or two will be over the area. No accumulation is expected. Mountian temperatures look to remain in the teens to 20'sF while ridgetop winds will be light from the east. 


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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 29  59 
Summit Lake (1400') 21  28 
Alyeska Mid (1700') 30  54 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 30  10 
Seattle Ridge(2400') 30  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 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

Subscribe to the Turnagain Area Avalanche Advisory:

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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