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Avalanche Advisory

Turnagain Area Avalanche Advisory
Friday, December 15th 2017 4:13 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 CONSIDERABLE on all aspects in the Alpine, 2500' and above. Triggering deep slab, 4-8+' deep, and/or a fresh wind slab 1-2' is likely on slopes steeper than 30 degrees. Cautious route-finding and conservative decision-making are essential. 

2500' and below the avalanche danger is MODERATE where rain has fallen and a melt-freeze crust has developed. Triggering a slab avalanche is still possible. 

Below 1000’, where little snow exists, there is no danger rating. 


 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.
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.
0 NO RATING Below Treeline / Below 1,000'
Special Announcement

The final accident report from the November 22nd avalanche fatality at Hatcher Pass is available HEREOur thoughts continue to go out to Randy Bergt's family, friends and ski partners.

Save the dates for two upcoming CNFAIC Fireside chats, December 19th at Blue & Gold Boardshop in Anchorage and December 21st at Powder Hound Ski Shop in Girdwood. Both will discuss lessons learned from past avalanche incidents.

Scholarship Applications are due TODAY! The Friends of the CNFAIC have two scholarships dedicated to avalanche education for skiers, snowmachiners and all user groups. The funds generated to make these possible are in celebration of Rob Hammel and Amy Downing, their love and passion for the mountains, and to help others stay safe. 


Avalanche Problem 1

Deep Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Above 2,500' moist to dry snow has fallen for two weeks now. We have little information for these upper elevations at this time, but we do know prior to the storm cycle weak faceted snow with crust(s) sat near the ground. Prior to this last warm, wet storm this set-up was very reactive and there were multiple remote triggered avalanches. The slab on top of this weak foundation has now grown to several feet. This presents a deep persistent slab problem and will be guilty until proven innocent.  The 1st person on the slope or the 10th might trigger this type of avalanche. It is a total roll of the dice or Russian roulette set-up. Finding the shallow spot could have devastating results. This type of avalanche would be unsurvivable. There may be no obvious clues to indicate instability and digging to find the weak layer could be challenging. We need more time and information to determine the sensitivity and distribution of the deep persistent slab problemConservative route-finding will be essential due to the potential for large avalanches. 

Below 2500' where rain fell the snowpack is a mixture of crusts and wet snow. Runnels are present and the facets near the ground are moist to wet and rounding. The cooling trend is locking up the snowpack. Triggering an avalanche is still possible but does not have the same potential for the large destructive deep slabs. Pay attention to your elevation bands today and as always look for signs of instability. 

Deep slab avalanches are like messing with a sleeping dragon. You might tiptoe around it but waking the dragon up will be terrible. Avoidance is key!

4-6+ inches of water weight, multiple feet of snow, now rest on top of this snowpack structure observed on December 8th. 


Avalanche Problem 2

Wind Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

In the Alpine there is plenty of new snow to blow around and an additional 2-6" is forecasted to fall throughout the day. Easterly winds gusting into the 40s will load leeward slopes today and triggering a fresh wind slab will be likely. Look for drifting and cracking and avoid hollow sounding snow. These same slopes may also have a deep slab problem. Triggering an avalanche in the upper snowpack may have the potential step down. 

Video from the National Avalanche Center Encyclopedia


Mountain Weather

Yesterday was overcast with light snow showers on and off throughout the day.   Easterly winds were light 5-10 with a few gusts into the teens. Temperatures were in the mid 20Fs to low 30Fs. There was a cooling trend overnight. 

Today is forecasted to be mostly cloudy with snow showers during the day with snow likely tonight. 2-6" of snow expected to fall today and 4-10" tonight. Temperatures will be in the mid 20Fs to low 30Fs. Winds will be easterly 15-25 gusting into the 40s. Rain/snow line will be approximately 500' today dropping to sea level tonight. 

Tomorrow should see continued snow showers, decreasing winds and cooler temperatures. According to the National Weather Service, "The long term will continue to see rather active weather, though cooler (more seasonable) temperatures should move back in." #snowtosealevel

* Sunburst weather station is down due to loss of battery power.
** Seattle Ridge anemometer is rimed and not reporting.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 30   0  0 25 
Summit Lake (1400') 28  0  0
Alyeska Mid (1700') 30  0  0  18

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') *n/a  *n/a  *n/a  *n/a 
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, 2018 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed as of April 20th
Placer River: ClosedClosed as of April 17th
Skookum Drainage: ClosedClosed as of April 1st.
Turnagain Pass: ClosedClosed as of May 7th. Happy summer, see ya when the snow flies!
Twentymile: ClosedClosed as of April 13th
Seward District
Carter Lake: ClosedClosed as of 4/27
Lost Lake Trail: ClosedClosed as of April 13th
Primrose Trail: ClosedClosed as of April 13th
Resurrection Pass Trail: ClosedClosed as of April 20th
Snug Harbor: ClosedClosed as of 4/27
South Fork Snow River Corridor: ClosedClosed as of April 13th
Summit Lake: ClosedClosed as of April 20th

Subscribe to the Turnagain Area Avalanche Advisory:

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
© 2018 Chugach National Forest Avalanche Information Center. All rights reserved.
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