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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Aleph Johnston-Bloom  
Saturday, February 11th 2017
Created: Feb 11th 4:27 am
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.
 Show the Complete North American Avalanche Danger Scale
Bear Tooth Theatre Pub & Grill
Special Announcement

As you make plans this weekend remember that many areas around Southcentral, Alaska including the Southern Kenai Mountains, Seward, Snug Harbor and Lost LakeAnchorage Front RangeHatcher Pass have had an unstable snowpack over the past few weeks. Human triggered large avalanches, breaking near the ground, are still possible. Please see links above for recent activity. Careful snowpack evaluation and cautious route-finding are recommended.  

TODAY: CNFAIC and the Anchorage Snowmobile Club will be hosting a FREE Avalanche Rescue Workshop at Turnagain Pass, 11am -12:30pm in the Motorized parking lot. We will focus on practicing with your beacon, probe and shovel. This workshop is open to everyone and anyone, PLEASE JOIN US!! Click HERE for more details. 

 


The Bottom Line

There is a MODERATE avalanche danger in the Turnagain Pass area. Triggering a fresh wind slab in leeward terrain is possible. In protected areas triggering a shallow storm slab or loose snow avalanche is also a concern. In addition, keep in mind that due to poor snowpack structure there is still a chance of triggering a large slab avalanche (2’-5’ thick) that breaks near the ground. 

Summit Lake: Make sure and check the Saturday Summit Summary HERE.


Primary Concern

The snow that fell yesterday was light and fluffy and the kind that will easily blow around and form tender wind slabs. Overall the winds weren't strong but there was period of more sustained wind last night. The new snow fell on surface hoar, near surface facets and sun crusts and was not bonding well. This should make winds slabs easy to trigger but due to limited snow totals the slabs shouldn't be that deep (6"-1'). Look for pillowed or drifted areas in leeward terrain and pay attention to shooting cracks. 

In areas not affected by wind there is also potential for shallow storm slabs and loose snow avalanches due to the new snow not bonding well to old snow surfaces. When the sun comes out today look for point releases on steep solar aspects. 

Storm snow easliy failing on buried surface hoar in a shovel tilt test yesterday.

Buried surface hoar over a micro sun crust @ 2200' on Sunburst yesterday.

 


Secondary Concern

Weak snow (facets and depth hoar) in the lower layers of the snowpack lingers as an issue in our advisory area. It has been 8 days since the last human triggered avalanches on these layers. However, triggering a deep slab is still a possibility if you find the wrong spot and a concern due to the depth of slab overlying the weak snow. The likelihood for someone to find and trigger a large slab is decreasing as the snowpack adjusts, but the poor snowpack structure remains and the consequences are scary. Both near miss avalanche accidents last week were triggered in thinner areas of the snowpack, on slopes that already had tracks on them. The tricky part about this particular avalanche problem is that it is very difficult to assess. Obvious signs like whumpfing and shooting cracks are unlikely and stability tests may not be reactive. Just because a slope has tracks on it does not mean it is safe. Likely places to trigger a deep persistent slab will be near rocks or in thin zones where affecting the weak layer is more of a possibility. Likely triggers are large: snowmachines, groups of people or cornice falls. Identify and avoid terrain traps (like large gullies).

Snow pit @ 2200' on Sunburst yesterday. Note the soft (weak, faceted snow) under the hard slab. 


Additional Concern

Last weekend cornice cracks were reported along the back bowls of Seattle Ridge. A few chunks have been triggered this week. Remember these unpredictable hazards can break farther back onto a ridge than expected and have the potential to trigger an avalanche on the slope below. Give cornices extra space and avoid being under them. 


Mountain Weather

Yesterday skies were obscured and light, low density snow fell throughout the day.  Temperatures were around 0 in the Alpine and teens/single digits in valley bottoms. Winds were mostly light and shifted from the West to the North. There was an uptick in winds that saw gusts up to 40 mph in the early evening. Light snow showers continued overnight. 

The chance for snow showers decreases this morning with clearing skies. Today temperatures will remain cold 3-13F and winds will be light and Northerly.  Tomorrow the pattern shifts as warm, moist air moves in with the first of a series of low pressure systems on track to affect the area. Stay tuned for details! 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880')  .3 58 
Summit Lake (1400')  1  .1  25
Alyeska Mid (1700')  6 6.5   .2  53

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  WNW-ENE 10 42 
Seattle Ridge(2400')  -1 NNE   5 21 

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: Apr 28, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: ClosedSKOOKUM DRAINAGE CLOSED TO MOTORIZED USE ON APRIL 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: OpenOpen thru May 14th.
Twentymile: Closed
Seward District
Carter Lake: OpenClosed May 1.
Lost Lake Trail: OpenClosed May 1.
Primrose Trail: OpenClosed May 1.
Resurrection Pass Trail: ClosedClosed for 2016/17 winter season. This is a non-motorized season. This alternates every other year and will open again during the 2017/18 winter.
Snug Harbor: OpenClosed May 1.
South Fork Snow River Corridor: OpenClosed May 1.
Summit Lake: OpenClosed May 1.

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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
© 2017 Chugach National Forest Avalanche Information Center. All rights reserved.
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