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Avalanche Advisory

Turnagain Area Avalanche Advisory
Tuesday, January 9th 2018 4:33 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 all slopes above 2,000' in elevation, where triggering a slab avalanche, breaking 1-3' deep on a weak layer of snow is possible. Slabs may release after several tracks are on the slope and avalanches may be triggered remotely. Additionally, triggering a larger slab breaking near the ground remains possible at elevations above 3,000'.

The danger is LOW near 2,000' and below.


 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.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Special Announcement
Our advisory page has changed! If you are not seeing new icons and the page doesn’t look right (icons are large, bar graphs are below them) please refresh this page and/or clean out your cache to see the changes.  Clean out your cache general link HERE.  For Google and Chrome the link is HEREInformation on the changes can be found HERE along with the video HERE. These changes are part of a national push to have consistency between public avalanche advisories across the country and to help better define the avalanche hazard each day. 
 
*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

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Above ~2,000' our concern is the New Year's storm snow that has now settled into a slab, around 12 - 20" at Turnagain Pass and 20-30" in the Girdwood Valley.  We have the buried surface hoar that was the cause for last week's avalanche activity that sits right under this New Year's snow. Could this slab/weak layer combination be triggered by the weight of a skier or snowmachiner? The answer is still YES. The buried surface hoar layer is slowly gaining strength and the slab is becoming more stubborn to trigger. However, snow pit results are still showing this layer to be reactive and to propagate - meaning human triggered slabs are possible if one hits the wrong spot on the slope. In addition, we are also concerned about slopes that avalanched in early December which have a thinner snowpack and harbor facets under the slab. Observers yesterday dug in a thinner spot on Sunburst and found reactive facets near the ground. 

On January 2nd it rained up to 2,000-2,300', creating melt-freeze crusts in the upper snowpack at these elevations and below, making triggering an avalanche unlikely in lower elevation terrain.

For those riders and skiers headed out today:

  • Keep in mind that travel in the upper elevations is where triggering a slab is most likely. This is above 2,000' where NO crusts exist in the top foot of the snowpack.
  • Remotely triggering a slab is possible, 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 are more suspect as well and those with rocky features.
  • Safe travel habits are always key, but especially when dealing with persistent and deep persistent slab avalanche problems: expose only one person at a time, have an escape route planned, watch your buddies closely and view all slopes as avalanche paths. If the snow does slide where will it go? Avoid terrain traps. 

 Wendy's video and photo from 3,000' on Sunday illustrate our current buried surface hoar issue well: 

Thin snowpack at 3400' on Sunburst. Note the weak faceted snow at the base under the slab. Photo: Sam Galoob

 


Avalanche Problem 2

Deep Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Still reading... Deep Persistent Slabs have been in the forecast every day starting December 14th. Unfortunately it is a concern that we can't ignore. At high elevations above 3,000’, human triggered large and dangerous deep slab avalanches are still possible. Weak sugary snow (basal facets) near the ground is creating a low probability/high consequence avalanche problem that is impossible to outsmart and will take a long time to heal. A big trigger like a snowmachine, more than one skier on the slope at the same time or a slab avalanche in the upper layers of the snowpack may be enough force to initiate a deep slab avalanche. Likely trigger spots will be in thinner areas of the snowpack that are connected to large, loaded slopes. Cautious route-finding is essential. This includes thinking about the remote trigger potential from below.

 


Mountain Weather

Yesterday was mostly clear and sunny above the valley fog. Temperatures were in the low 20Fs at upper elevations and in the teens to single digits in the valley bottoms. Winds were mostly light and variable. 

Today there will be patchy valley fog in the morning but that should dissipate as cold dry air pushes into the region. Winds will be northerly 5-15 mph with gusts into the 20s. Temperatures will be in the low 20s and high teens today, dropping into the low teens and single digits tonight. 

Tomorrow will be partly cloudy with a chance of snow showers in the afternoon and temperatures in the high teens and low 20Fs. Winds will be from the SE 10-20mph. The weather looks to be unsettled into the weekend with snow showers and warming temperatures. Stay tuned! 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 24  43 
Summit Lake (1400')  6  15
Alyeska Mid (1700')  18 0  36

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 22  variable   4 15 
Seattle Ridge(2400')  21  10  23

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
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