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Avalanche Advisory

Turnagain Area Avalanche Advisory
Monday, December 31st 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

Strong winds and new snow have created dangerous avalanche conditions. The avalanche danger is CONSIDERABLE at all elevations today. Triggering a large slab avalanche 1-3' feet thick will be likely on slopes steeper than 30 degrees and natural avalanches are possible. Cautious route-finding and conservative decision-making are essential today. Avoid travel under cornices and glide cracks. Pay attention to changing conditions. If the next storm moves in earlier than forecast the danger will bump up to HIGH and natural avalanches will be likely. 

GIRDWOOD: Roof avalanches are real hazard with warming temperatures and rain on snow. Pay attention to children and pets and where you park your car. 

SUMMIT LAKE / JOHNSON PASS / LYNX DRAINAGE:  South of Turnagain Pass, keep in mind weak layers near the ground and the potential for large avalanches. 

 

 

 


 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.
3 Considerable Treeline / 1,000'-2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
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 are considering Hatcher Pass today, PLEASE check HPAC's Saturday avalanche forecast. A close call occurred at Hatcher on Friday and tricky snowpack conditions exist, read the report HERE

  •  There will be intermittent traffic delays today on the Seward Highway for avalanche hazard reduction work between Girdwood and Portage near mileposts 82 to 89. Motorists should expect delays of up to 45 minutes between 12:00 Noon and 1:30 PM. Updates will be posted on the 511 system. http://511.alaska.gov/

Avalanche Problem 1

Storm Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Human triggered (skier or snowmachiner) storm slabs are likely today on slopes steeper than 30 degrees. The first in the series of storms forecast to impact the area is moving out this morning. The storm brought sustained strong winds yesterday and last night and heavy snow overnight. Do not let the potential for decent visibility today lure you into avalanche terrain. Look for signs of instability. Recent avalanches are the best clue that the snowpack is unstable. 

24-hour precipitation and wind:

  • Turnagain Pass SNOTEL: 15" (1.3" SWE), Sunburst wx station winds: NE, 25-40 mph, gusting to 102
  • Girdwood – Alyeska Midway: 20” (1.5” SWE), Max's wx station winds: E-NE 25-40 mph, gusting to 92
  • Summit Lake: 3-6" (0.3” SWE)

With the strong winds and new snow we expect a buffet of storm related avalanche issues today. New snow was landing on a layer of surface hoar and may not bond well to the old snow. The temperatures increased during the storm putting heavier snow over lighter snow. Storm slabs may be very sensitive. Look for cracking and collapsing. With the buried surface hoar potential these slabs may be very reactive even on slopes in the Tincan Trees. Remote triggering may be possible. Avoid travel in runout zones. 

Wind slabs: Strong winds will have the blown snow into the leeward start zones. Due to the high wind speeds slabs may have formed further down the slope than expected. Look for pillowing, drifting and cracking. Be suspect of hollow sounding snow or hard snow over soft snow. 

Cornices: High winds and blowing snow will have added to already large cornices. These may be very sensitive and a cornice fall could trigger a large avalanche on the slope below. Remember these can break further back than expected. 

 Heavy snow overnight on Turnagain Pass.

Surface hoar observed 12-28-18, Photo: Trip Kinney


Avalanche Problem 2

Glide Avalanches

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Glide avalanches have been releasing over the past week. Remember these avalanches are not triggered by people and are unpredictable. The most recent release of a glide crack (glide avalanche) was noted Saturday on Lipps. The new snow may have covered some of the glide cracks up. Don't forget they are looming over popular ski and snowmachine terrain and limit as much time under them as possible! The glide cracks are on the move... Don't mess with the brown frown!

 Lipps glide avalanche, 12-29-18. Photo: Andy Moderow


Additional Concern

Persistent Slabs

South of Turnagain:  As we have been mentioning for some time, a shallow and poor snowpack structure exists in the Summit Lake zone. Buried weak layers of facets associated with crusts sit 1-3' below the surface near the base of the snowpack. Although Summit did not get much precipitation in this first storm it will be important not to forget the possibility of triggering a larger avalanche that could release near the ground if recreating in that zone. Check out the Summit observations HERE for the most current information. 


Mountain Weather

Yesterday: Skies were overcast to obscured with snow and rain showers throughout the day intensifying overnight. Rain/snow line was around 500'. Winds were easterly 25-40 mph gusting as high as 102 on Sunburst. Temperatures were in the 20Fs to mid 30Fs. 

Today: Skies will be mostly to partly cloudy. There is a chance of snow showers during the day. Winds will be easterly10-20 mph with gusts into the 30s. They shift to the north this afternoon and ease up briefly. Temperatures will be in the high 20Fs to mid 30Fs. This evening the next storm moves into the area with easterly winds increasing 20-40 mph gusting into the 50s. Precipitation may be heavy again with rain/snow line around 800'-1000'. 

Tomorrow: Rain and snow in the morning decreasing in the afternoon. Winds will decrease as well. Temperatures will be in the high 20Fs to high 30Fs. The pattern remains active for the week but the model confidence remains low. Stay tuned for storm details. 

*Seattle Ridge weather station was heavily rimed and the anemometer (wind sensor) was destroyed.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 30  15  1.3  67 
Summit Lake (1400')  30   3 0.3  15 
Alyeska Mid (1700') 30   20  1.5  55 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 20  NE  38   102  
Seattle Ridge(2400') 25  *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: May 06, 2019 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed as of 4.3.19
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: ClosedClosed as of 5/6. Thanks for a great season all, see you next winter!
Twentymile: ClosedClosed as of 3.20.19 due to lack of snow.
Seward District
Carter Lake: Closed
Lost Lake Trail: ClosedClosed as of 3.22.19 due to lack of snow
Primrose Trail: ClosedClosed as of 4.3.19 due to lack of snow
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: ClosedClose as of 5.1.2019
South Fork Snow River Corridor: ClosedClosed as of 3.20.19 due to lack of snow.
Summit Lake: Closed

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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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