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Avalanche Advisory

Turnagain Area Avalanche Advisory
Sunday, February 3rd 2019 7:00 am by Wendy Wagner
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche danger is expected to rise to CONSIDERABLE today in areas above treeline receiving new snow and wind. Expect fresh wind slabs to be easy to trigger and relatively shallow, up to a foot thick. The more concerning issue is, newly wind loaded slopes are overloading a weak layer of buried surface hoar 1-3' deep in the snowpack. Due to this poor set-up, large and unsurviveable human triggered slab avalanches remain possible on slopes over 2,000'

SUMMIT LAKE / JOHNSON PASS:  Human triggered slab avalanches 1-3' thick remain possible above treeline as a variety of weak layers exist in the snowpack. Wind loaded slopes are the most suspect for triggering an avalanche. 

LOST LAKE:  We have had reports that avalanches are being easily triggered on wind loaded slopes in the Lost Lake area. New snow and wind is expected to increase the avalanche danger in these areas near Seward today. 


 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.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Special Announcement
  • Headed to Hatcher Pass? Make sure and check HPAC's advisory HERE!
  • GET your tickets now! SNOWBALL Feburary 7th, 2019: This anual fundraiser supports CNFAIC and Alaska Avalanche School with a silent auction and a raffle.  Don't miss this opportunity to celebrate our awesome winter season with the funk band Superfrequency at the 49th State Theater in Anchorage. This show sells out! 

Avalanche Problem 1

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Another round of snow and wind is on the doorstep today and into tonight. Turnagain only looks to receive a few inches out of this and Girdwood/Portage areas up to 6" or more. What this will do to the snowpack is add an incremental load, which in our current snowpack set-up is significant. We did not receive any reports of avalanches being triggered yesterday, however on Friday (Feb 1st) several large slab avalanches were triggered. All of them failed on a weak layer of buried surface hoar 1-3' below the surface. They are summarized in yesterday's avalanche forecast if you missed it.

The concerning thing is, these avalanches are hard slabs, propagating across entire slopes and proving to still be reactive. They have been predominantly triggered remotely from or near ridgelines. Although the avalanches triggered so far have been in the Seattle Ridge zone, this weak layer is known to be widespread in the region. With another load of wind deposited snow today, these hard slabs on buried surface hoar are being pushed more toward their tipping point. The size and scope of this avalanche problem is nothing to mess with. Cautious route-finding is essential and steering clear of avalanche terrain above the trees is a good way to avoid the hazard. No signs of instability are likely to be present before a slope releases and therefore, we have to remember a bad layer is lurking below our feet.

 

Jr's Run avalanche, triggered remotely from the ridge on February 1st (you can see snowmachine tracks along the ridge if looking close). Photo taken February 2nd. Although this looks like three separate slides, these were all triggered close to the same time from the ridge. Interesting how the middle portion remains intact.

 

Widowmaker avalanches, triggered February 1st. The 'Looker's right' avalanche was triggered remotely from the ridge an hour or so after the main path ran. The main path was triggered near the crown by a snowboarder and that crown wraps around, out of view to the left side of photo. Very impressive, and scary, propagation.

  

 

The thin gray line the arrow points to is the weak layer under the surface we can't forget about. 


Avalanche Problem 2

Wind Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Ridgetop winds are picking up this morning from the east and expected to blow in the 25-35mph range today. With loose surface snow and 2-4" of new snow available to transport, wind slabs on leeward slopes should be expected. These are expected be fairly shallow, a foot or less in thickness, yet could be easy to trigger. 


Additional Concern

Glide Avalanches

It appears that glide cracks are opening again and a glide avalanche released in the Summit zone recently. Heads up to look for glide cracks and limit exposure under them!

Glide avalanche on a southerly slope just north of Manitoba. First noticed Feb 1st. Photo: Patrick Machacek


Mountain Weather

Yesterday:  Partly cloudy skies and sunshine filled the region yesterday. Ridgetop winds were light and variable during the day and have switched to the east overnight, increasing to the teens with gusts to 30mph. Temperatures were civil, in the 20'sF at sea level and valley bottoms with the teens along ridgelines. 

Today:  A southwest flow is ushering moisture up Cook Inlet, bringing snow to the western Kenai mountains and setting the stage for significant snow in the Hatcher Pass area. This flow direction typically leaves Girdwood and Turnagain out of the fun. We can expect cloudy skies with 2-4" of snow today and another 2-4" tonight. Ridgetop winds will be 25-35mph from the east with stronger gusts. Temperatures look to rise to near 32F at sea level, bringing a rain/snow mix, while ridgetops should remain in the teens.

Tomorrow:  A brief break between fronts may clear skies tomorrow during the daylight hours before warmer air and precipitation heads in later in the day and into Tuesday. An active pattern seems to be in place for most of the coming week. 

*The Seattle Ridge anemometer (wind sensor) was destroyed. We are currently working to replace it. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 21  57 
Summit Lake (1400') 19  23 
Alyeska Mid (1700') 21  0.14  47 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 17  variable  8 30 from east 
Seattle Ridge(2400') 18  *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, 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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