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Avalanche Advisory

Turnagain Area Avalanche Advisory
Monday, February 25th 2019 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 on slopes over 35 degrees above 2,000'. Triggering a slab resting on weak faceted snow is still possible. Slabs could be anywhere from 6" to 2' thick depending on prior wind-loading. Additionally, pay attention to changing conditions with warm temperatures in the Alpine, especially on steep slopes in direct sunshine. As always, give cornices a wide berth and limit exposure under glide cracks.

SUMMIT LAKE / JOHNSON PASS:  Triggering a larger, more dangerous slab remains a concern due to variety of old weak layers in the mid and base of the snowpack. Extra caution is advised. Evaluate snow and terrain carefully. 

SEWARD / LOST LAKE:  Slabs up to 2' in depth could be found and triggered in this area on steep wind-loaded slopes.


 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.
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 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.


Avalanche Problem 1

Persistent Slabs

Almost Certain
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Unlikely

Chance

Historic
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Size

With a strong inversion in place some Alpine weather stations are already near or above freezing this morning. Alyeska Summit (3664') is at 35F and the base of Alyeska (100') is at 13F. Sunburst (3812') is at 30F and Turnagain Pass DOT (1020') is at 7F. Summit Lake MP 45 (3800') is at 36F and Summit Lake DOT (1348') is at 4F.  This is the first day to see temperatures above freezing at upper elevations. It will be important to pay attention to changing conditions. This can sometimes make triggering an avalanche on a persistent weak layer more likely. Be most suspect on steep slopes getting direct sunshine. Look for roller balls and wet sluffs, signs that the snow is heating up. The slab avalanche issues today revolve around older weak layers within the snowpack (persistent weak layers). The most recent weak layer (the Valentine's near surface facets) sits around a foot deep under the wind affected snow and old wind slabs. This layer has been showing signs that it could still be reactive if you find the trigger point. There was a small skier triggered avalanche observed yesterday looker's right of Ragged Bowl (near Girdwood) that is suspected to have run on this layer. The second layer down is the MLK Jr buried surface hoar. Although found throughout the advisory area this layer is showing signs of only being reactive in the Summit Lake zone. Additionally in the Summit Lake region there is weak snow near the ground. 

If you are headed out today watch for:
    -  Wind-loaded, steep, unsupported slopes are the most suspect for popping out a wind slab that may be sitting on weak snow.
    -  Larger and more dangerous avalanches are possible in the Summit Lake and Johnson/Bench peak area where a thinner snowpack exists.
    -  SUN EFFECT and moist/wet sluffs on steep rocky southerly terrain. 
    -  Cornices. Warmer temperatures at higher elevations can help loosen these monsters and with good weather and ridgeline travel, don't forget to give cornices a wide berth.
 And remember to practice safe travel protocol

Observer on Max's yesterday found no signs of instability but found the buried Valentine's facets to still be reactive, 2.24.19

 

Large natural avalanches triggered by high winds on 2.21.19 in Summit Lake. If heading that way remember the snowpack is harboring a number of weak layers. 


Additional Concern

Glide Avalanches

Glide cracks are unpredictable, not associated with human triggers, and can release without warning at any time.  The best way to manage this problem is to avoid traveling on slopes directly below glide cracks. A short list of known cracks in popular zones:  Magnum, Lipps, Seattle Ridge, Eddies, Lynx Ck. See a new glide crack or one that appears to be opening up? Please snap a photo and send us a quick ob!


Mountain Weather

Yesterday: Mostly sunny with some high clouds, very light westerly winds and temperatures in the 20Fs in mid to upper elevations. Overnight valley bottoms saw temperatures in the single digits with the inversion in place. 

Today: Mostly sunny with a chance of valley fog in the morning. Light winds. With the temperature inversion early morning temperatures in the Alpine are near or above freezing and valley bottoms are in the teens to single digits. Valley bottoms temperatures are forecast to rise into the 20Fs and then dip back down overnight. Upper elevations should stay in the 30Fs to high 20Fs. 

Tomorrow: The ridge of high pressure looks to dominate the weather pattern and similar weather looks to be on tap for the remainder of the week with the high temperatures slightly increasing each day and lows in the teens at night in the valley bottoms. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 23  61 
Summit Lake (1400')  12   29 
Alyeska Mid (1700') 24   0    0    56  

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  24  SW
Seattle Ridge(2400')  24   NW   1    6  

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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