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Avalanche Advisory

Turnagain Area Avalanche Advisory
Thursday, January 11th 2018 4:38 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 today due to new snow falling on weak surface snow and increasing winds. Watch for changing conditions as the storm moves. In the Alpine triggering a slab avalanche, breaking 1-3' deep on a weak layer of snow remains possible. Additionally, triggering a larger slab breaking near the ground remains possible at elevations above 3,000'.  


 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
Our advisory page has changed! Information on the changes can be found HERE
 
*Coming up on January 13th there is a FREE avalanche rescue clinic at Hatcher Pass. Practice with your gear on your way to the backcountry - clinic runs from 11am - 1:30pm. 

 


Avalanche Problem 1

Storm Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Today is a transition day. We have had mostly cold, clear weather this week. Snow is forecasted to start falling this morning and winds are increasing, gusting into the 30s. The new snow will be falling on very weak surface snow. There is widespread surface hoar, with near-surface facets below.  In the terrain around  2000' and below, this weak snow is more developed and is sitting on the New Year's melt-freeze crust. This has the potential to act as a bed surface. As the weather comes in today it will be important to pay attention to changing conditions. Slabs may form quickly, especially in leeward terrain. Quick hand pits or riding small terrain features can help check whether or not the new snow is sticking to the old snow surfaces. In steep terrain the weak surface snow can also act as a few inches of fast moving loose surface snow “sluff” that could catch you by surprise if you’re not expecting it. 

Surface hoar in the sunshine on Tuesday at 1700' on Sunburst, photo: Ray Koleser.


Avalanche Problem 2

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

As we anticipate the weak snow on the surface getting buried today don't forget the old buried weak layers.  The chances of triggering a persistent slab avalanche have been decreasing. However, it is not something that should totally be ruled out yet. We know that the snow from the New Year's storm snow is sitting on either buried surface hoar, buried near-surface facets or in thin snowpack areas, facets near the ground. This means there is poor snowpack structure and a persistent slab set-up above 2500'. Snowpack tests over the past few days have shown variable results but point to the continued potential for triggering an avalanche.

For those riders and skiers headed out today:

  • Triggering a slab is most likely in the upper elevations above 2,500', where NO crusts exist in the top foot of the snowpack.
  • Several tracks may be on the slope before a slab releases and no signs saying 'the slope is unstable' are likely to be present.
  • Larger slopes, 35 degrees and steeper are more suspect and those with rocky features. 
  • Practice safe travel habits: expose only one person at a time, have an escape route planned, watch your buddies closely and view slopes as avalanche paths. If the snow does slide, where will it go? Avoid terrain traps. 

Watch Wendy's Extended Column Test from yesterday, January 10th, on Seattle Ridge. It took some harder hits but still propagated (failed across the weak layer). This layer could still produce an avalanche.

Wendy's pit yesterday was near her pit location on Sunday. She had very similar results. The slab yesterday was a little deeper. 

 


Additional Concern

Deep Persistent Slabs

A poor snowpack structure still exists at high elevations above 3,000’, human triggered large and dangerous, deep slab persistent avalanches are still possible. Weak sugary snow (basal facets) near the ground is creating a low probability/high consequence avalanche problem. Likely trigger spots will be in thinner areas of the snowpack that are connected to large, loaded slopes. Signs of instability will not likely be present and there may be tracks on the slope. The possibility of a deep slab avalanche should still be part of your decision-making before committing to big terrain in the Alpine. 

 


Mountain Weather

Yesterday was a mixture of obscured to overcast to broken skies. Winds were in easterly 10-20 mph, gusting to 30. There were scattered, very light snow showers in the morning. Temperatures were in the teens to low 20s. Overnight temperatures rose as warm air moved into the area. 

Today will be mostly cloudy with snow, 4-9" forecasted. Winds will be easterly 20-30 mph gusting into the 40s. Temperatures will be in the high 20s. Snow will continue overnight into Friday.

Friday afternoon the temperatures are forecasted to rise and Saturday looks like a shift to liquid precipitation at lower elevations. The pattern of the warm southerly flow combined with a series of low pressure systems could persist into next week. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 26   0 0 42 
Summit Lake (1400') 15   0 14
Alyeska Mid (1700')  22  0 34 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  13  ENE 11  31 
Seattle Ridge(2400')  17  SE 16 31 

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: Dec 01, 2018 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed
Placer River: ClosedClosed
Skookum Drainage: ClosedClosed
Turnagain Pass: ClosedClosed November 21 due to inadequate snow conditions. #hopeforsnow
Twentymile: ClosedClosed
Seward District
Carter Lake: ClosedClosed
Lost Lake Trail: ClosedClosed
Primrose Trail: ClosedClosed
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: ClosedClosed
South Fork Snow River Corridor: ClosedClosed
Summit Lake: ClosedClosed

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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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