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Avalanche Advisory

Turnagain Area Avalanche Advisory
Saturday, April 6th 2019 7:00 am by Heather Thamm
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 today at all elevations. Triggering a wind slab up to 10" thick will be possible on steep leeward features due to new snow and strong wind. Below 3000' glide cracks may avalanche without warning in popular terrain. Plan your route to avoid traveling under existing cracks. Additionally triggering a wet loose avalanche may be possible with rain in the lower elevations if surface crusts become unsupportable. Be prepared for natural wet loose activity on solar aspects in the alpine if the sun makes an appearance today.

PORTAGE VALLEY: Summer trails with avalanche terrain overhead, such as Byron Glacier Trail, are not recommended due to the possibility of an avalanche or cornice fall sending debris over the trail.


 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.
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.
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. Check in at any Ski Patrol station or visit the Snow Report for the location of the search park.
  • Are you wondering what the snowpack is like in Hatcher and Chugach State Park with all this warm spring weather? Check out Hatcher Pass Avalanche Center Saturday advisory and recent observations from Chugach State Park and consider bringing bear spray. 

Avalanche Problem 1

Wind Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
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Large
Small

Size

Warm temperatures and Low pressure in the Gulf of Alaska will bring rain to ~2000’ today and snow showers above. In the alpine Easterly winds 20-35mph will form isolated wind slabs on leeward terrain features. The size of these wind slabs will depend on how much snow falls. Areas closer to the coast (Portage, Girdwood and North end of Turnagain Pass) could see 4-6” of snow by early evening. Interior areas will see less precipitation. New snow will be falling on a variety of slick surfaces and bonding may be poor. Surfaces include firm crusts on W-S-E facing aspects in the alpine and surface hoar and near surface facets on shaded Northern aspects. Look for blowing snow, shooting cracking - steep leeward terrain features will be the most suspect for triggering a wind slab. Keep in mind its spring-time and be ready for wet loose activity on solar aspects if the sun comes out.

WET LOOSE: In the lower elevations below 2000’ where a stout crust has formed rain will start to soften this surface crust. If this crust starts to deteriorate and become wet and unsupportable, triggering a wet loose avalanche in steeper terrain will be possible.

CORNICES: Cornices remain very large along some ridgelines in the alpine. Give them a wide berth and avoid travel directly below them.

South of Turnagain in Summit Lake and areas in the interior Kenai Peninsula have a variety of old weak layers within the snowpack. The last observed slab avalanche was 10 days ago on the West face of Butch. A stout crust has formed on all elevations below 3000’ and on solar aspects in the alpine. Triggering a persistent slab 2-3’ deep is becoming an outlier at this time, but worth noting if headed to Summit Lake. Be aware of a variety of avalanche conditions ranging from small isolated wind slabs to wet loose. This area is more likely to see sun in the afternoon. Otherwise conditions are very similar to Turnagain.

Wind slabs will be forming on a variety of surfaces. Surface hoar  has been seen on North aspect (top photo) and stout crusts (bottom photo) on all aspects below 3000' and W-S-E aspects in the alpine.

 


Avalanche Problem 2

Glide Avalanches

Almost Certain
Very Likely
Likely
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Unlikely

Chance

Historic
Very Large
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Glide cracks have been opening and releasing across our region over the last two weeks. This is the entire snowpack gliding downhill and spontaneously releasing. So far all of this activity has occurred on East, South, and West facing slopes below 3000’. This week Turnagain Pass has been the most active. Glide avalanches are not associated with a human trigger and release without warning. These avalanches, even small ones, are extremely destructive. The best way to manage this problem is avoidance. Identify existing cracks and plan your route to avoid being under a glide. Many cracks are opening in popular terrain and may require an unusual route to avoid their runout. This is a case of 'don't be caught in the wrong place at the wrong time'.

Recent glide avalanches and lots of glide cracks on popular terrain in Turnagain. From left to right - Magnum, Corn Biscuit, and Lipps - SW aspects


Mountain Weather

Yesterday: Skies were sunny to partly cloudy. Temperatures reached the mid 40Fs to low 50Fs at sea level. Ridgetop temps were in the upper 20Fs during the day and dropped to the low-20Fs overnight. Ridgtop winds were light from the Northeast increasing into the 20s mph overnight. Light rain starting falling this morning with 0.1" recorded at Turnagain Pass. Rainline is estimated around 1800'.

Today: Snow showers are expected above 2000' 4-6" of snow possible. Rain is expected in the lower elevations with up to 0.5" of rain. Areas further from the coast will see less precip today and a chance for broken skies in the afternoon. Easterly ridge top winds are expected to be 20-35mph. Temperatures at sea level will be in the mid-40Fs and temps along ridgetops may reach the low-30Fs.

Tomorrow: Scattered snow and rain showers are expected on Sunday. Easterly Ridgetop winds will decrease to 5-15mph. Light precipitation is expected with rain below 2500' and a few inches of snow possible in the upper elevations. Temperatures at sea level will be in the 40Fs to low 50Fs. Ridge top temps are expected to range from mid-20s to low-30Fs.

**SNOTEL data for Center Ridge and Summit was unavailable after 5am (reads 4am due to daylight savings.) 24-hour precip for Turnagain was recorded on the Turnagain DOT RWIS weather station. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 35  **0.1  65 
Summit Lake (1400') 35  20 
Alyeska Mid (1700') 36  .01  57 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 25  ENE  24 
Seattle Ridge(2400') 31  ESE  11 

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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