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Avalanche Advisory

Turnagain Area Avalanche Advisory
Saturday, March 9th 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

The avalanche danger is CONSIDERABLE this morning due to 1-2 feet of new snow in the past 24-hours. The danger is expected to rise to HIGH this evening as another round of snow and wind moves in. Human triggered slab avalanches, up to 2+ feet thick, will be likely. Natural avalanches will be possible. The new snow is falling on a very weak base and expected to slide easily on steep slopes. We are entering spring break with a dangerous avalanche situation and restraint will be required as travel in avalanche terrain is not recommended. 

PORTAGE VALLEY: Natural avalanches are possible today that could send debris to valley floors. Areas with steep slopes and avalanche terrain above you, such as the Byron Glacier Trail, should be avoided.

SUMMIT LAKE:  Despite little new snow, this area has a very shallow snowpack with multiple weak layers. Strong winds and the potential for a few inches of new snow today could overload buried weak layers, producing an unexpected slab avalanche. Caution is advised if heading to this area.

LOST LAKE:  Dangerous avalanche conditions are expected in the Lost Lake and Seward regions as well due to 1-2 feet of new snow and strong winds. 


 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.
4 High Treeline / 1,000'-2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
3 Considerable Below Treeline / Below 1,000' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
Special Announcement
  • If you’re headed to Alyeska today, bring your avalanche beacon. Backcountry Access (BCA) and Alyeska Ski Resort will have a beacon training park set up all day on March 9, March 23, and April 6. Check in at any Ski Patrol station or visit the Snow Report for the location of the search park.
  • Heading to Hatcher Pass? Be sure to check out the Hatcher Pass Avalanche Center Saturday avalanche forecast HERE.

Avalanche Problem 1

Storm Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

It's a simple equation:  new snow falling on a slippery surface + wind loading = easily triggered avalanches.

Heads up for anyone headed out today. Storm snow avalanches are expected to be easily triggered. These will be in the form of wind slabs on wind loaded slopes, storm slabs in areas out of the wind, cornice falls and new snow sluffs. The size of the avalanche will depend on the amount of new snow and wind loading. In the Girdwood Valley slabs could be up to 3' thick on wind loaded slopes. In the Turnagain Pass area, slabs could be up to 2' thick. Come tomorrow, add another 10-20" to the thickness of these slabs. 

Although hidden from view, under the storm snow is the old surface, which is a combination of sun and wind crusts, facets and surface hoar. Not only will this old surface inhibit bonding with the new snow, it may also allow slabs to propagate wider than expected. Remotely triggered avalanches are also possible, meaning triggering a slide from the ridge or the bottom of a slope. With another round of snow and wind slated to hit later today, pushing the danger to HIGH, now is the time for us to keep out of avalanche terrain and let the mountains do their thing. 

Estimated storm totals (mid-upper elevations) beginning Thursday ending Saturday 6am:

  • Turnagain Pass:  10" - 16" snow (1" water)
  • Girdwood Valley:  16 - 24" snow (1.5 - 2.3" water)
  • Summit Lake:  1-2" snow (0 - 0.1 water)
  • Bear Valley (Portage):  20 - 30" snow (2 - 2.5" water)
  • Seward area:  12" - 20" snow (1-1.5" water)

 Rain has been falling below 1,000' and expected to continue today. This whas saturated the low elevations and wet sluffs will be possible. 

Storm slab avalanche in the Tincan Trees from yesterday. Roughly 6 more inches of snow has fallen with more on the way, which will create much larger slabs for today. Photo: Allen Dahl.

 

The photo above shows the 6-8" of new snow from yesterday sliding easily on the old sun crust that was the surface a few days ago. (Photo: Allen Dahl)


Mountain Weather

Yesterday:  Light to heavy snowfall was over the region as the second storm front passed through. Rain fell up to 500' and in some areas up to 1,000'. Snowfall amounts across the region varied greatly from only a trace in the Summit Lake area to over 2 feet in the upper Girdwood and Portage Valleys. Turnagain Pass has seen around a foot of new snow. Ridgetop winds over the past 24-hours have been blowing 20-30mph from the east with stronger gusts. Temperatures have been steady in the low to mid 20'sF along ridgelines and in the mid 30'sF near sea level.

Today:  A brief break between storms is expected this morning with the third wave of precipitation moving in midday and peaking late tonight. An additional 3-6" of snow is expected to fall today with 10-14" tonight. The snow/rain line should creep up to 1,500' in areas and therefore, rain will be falling at the low elevations. Ridgetop winds are forecast to remain easterly in the 20-30mph range with gusts up to 50mph. Temperatures may reach the upper 40F at sea level, 32 at the mid elevations and the mid 20'sF along ridgelines.

Tomorrow:  Stormy weather will continue Sunday and into Monday with an additional 6-12" of snow at the mid and upper elevations. Cooler air looks to be entrained on Monday, which will lower the rain line and snow could fall near sea level. Another small break in storms may occur Tuesday before another round of precipitation hits. Stay tuned!

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 31  10  0.8 63 
Summit Lake (1400') 33  trace   0 26 
Alyeska Mid (1700') 30  14  1.05  67 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 21  NE  29  57 
Seattle Ridge(2400') 27  SE  14  27 

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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