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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Tuesday, January 3rd 2017
Created: Jan 3rd 5:48 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.
1 Low Treeline / 1,000'-2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
 Show the Complete North American Avalanche Danger Scale
Special Announcement
  • As of yesterday Alaska DOT has not cleared the Turnagain Pass motorized lot. Please park safely and be respectful of any plow efforts to clear this lot. 

  • If heading to Hatcher this New Year - unstable conditions exist - check the Hatcher Pass advisory HERE Mark your calendars for the FREE rescue workshop at Hatcher Pass on January 14th. More info HERE.
  • For Turnagain Pass December Weather History Chart click HERE.

The Bottom Line

A MODERATE avalanche danger remains in the alpine where triggering an isolated wind slab or a deeper slab 2+’ thick is possible on steep wind loaded slopes that haven’t avalanched. Within the trees and at lower elevations there is LOW avalanche danger, where triggering an avalanche is unlikely, but not impossible.

In the periphery zones of Girdwood, Johnson Pass and Summit Lake a much shallower snowpack exists and it may be easier to trigger a slab avalanche in these areas.  Check out the Summit Lake Summary HERE and click HERE for a recent observation from Max's Mountain in Girdwood. 

 


Primary Concern

PERSISTENT SLAB AVALANCHES (In our current case: Hard WIND SLABS SITTING ON WEAK SNOW): Its been 4 days since a big wind event loaded Northern aspects and cross loaded many Eastern aspects. This wind event as well as the Christmas snow storm (a week ago) caused widespread avalanching in the area. Several persistent weak layers are buried within the snowpack (facets and buried surface hoar), but strong supportable snow over top is making it stubborn to trigger. In the periphery areas (Girdwood, Johnson, Lynx, Summit Lake and even Kickstep) where a thinner snowpack exists several observers have experienced collapsing/wumpfing in recent days. Including an observer who felt/heard a loud collapse followed by a fast moving shooting crack on their second ascent up Max’s Mountain on Sunday. It will be in these areas where finding unstable snow may be easier. 

If you were out yesterday you probably noticed an extreme temperature inversion. Some ridgetops reached 40F while valley bottoms remained in the single digits (F). Today looks similar. Luckily this warming trend did not melt the surface snow and radiation is minimal at this time of year. However when temperatures remain above freezing for several days it should warrant caution. Be skeptical of steep loaded slopes that haven’t avalanched yet. Likely trigger spots will be in thinner areas of the snowpack in steep rocky terrain or on unsupported slopes that may harbor just the right set-up for a person or snowmachine to tip the balance. Obvious signs like cracking and ‘wumpfing’ are becoming less common in the Turnagain Pass area and may not be an early warning sign. The problem with hard slabs, as noted by local ski guide and avalanche educator, Joe Stock, “They let you get out in to middle with no feedback, then they crack far uphill from you.”  Be sure to check out Stock’s excellent discussion on Close Calls With Avalanches.

This is why we should always practice safe travel habits to minimize exposure in avalanche terrain! 

  • Expose one person at a time
  • Watch your partner from a safe zone
  • Have an escape route planned
  • Watch for other groups

These slabs on the North side of Tincan likely released during the Dec.30th wind event. This a good example of where pockets of poor snowpack structure may linger. It is in these places where practicing safe travel protocals is very important. Photo taken 1/2/17

 


Mountain Weather

Yesterday skies were sunny with light Northwest ridge top wind. A large temperature inversion was observed, valley bottoms were in the single digits (F) and ridge tops reached 40F. A thick valley fog filled Turnagain Arm. 

Overnight ridge top temps dipped slightly into the mid-30F’s and valley temps averaged around 10F.  Winds have remained light and no precipitation was recorded. 

Today expect a similar inverted weather pattern with above freezing temperatures near ridgetops. Northwest ridge top winds are expected to pick up today, 10-20mph. Dense Valley fog may linger in and along Turnagain Arm. 

A dominent high pressure is positioned over Interior and Southcentral, Alaska. The latest weather discussion mentions the potential for strong gap winds Wednesday night thru Thursday and cooling upper elevation temperatures. This could bring a windchill factor well below zero (F.)

An impressive photo taken yesterday of recent surface hoar growth (~4" long) found on Center Ridge. Don't worry this on the surface of the snow and doesn't present any current concerns. Photo courtesy of Sam Galoob



Thick valley fog along Turnagain Pass yesterday was a result of the extreme temperature inversion in our region. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 30  37 
Summit Lake (1400') 12  11 
Alyeska Mid (1700') 29  25 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 36  NW  14 
Seattle Ridge(2400') 37  NW  17 

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: Mar 25, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: OpenPlease park on road in and leave the turnaround (near outhouse) open for trailers to turn around.
Placer River: Open
Skookum Drainage: OpenSkookum drainage closes to motorized use on April 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: Open
Seward District
Carter Lake: Open
Lost Lake Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Primrose Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
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: Open
South Fork Snow River Corridor: Open
Summit Lake: Open

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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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