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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Monday, January 30th 2017
Created: Jan 30th 5:31 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.
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.
 Show the Complete North American Avalanche Danger Scale
Special Announcement

Dangerous avalanche conditions persist in many areas around Southcentral Alaska
including the Southern Kenai Mountains, Hatcher Pass and Anchorage Front Range

  • A preliminary report is out with a few photos regarding the snowmachine avalanche fatality in the Snug Harbor area on Saturday. The final report with finalized details on the events, rescue and snowpack analysis will be posted in the next couple days. Our thoughts continue to be with the victim's family, friends and rescuers.
  • The Southern Kenai Mountains, including Snug Harbor and Lost Lake zones continue to have dangerous avalanche conditions. This region is out of the advisory area but large human triggered slab avalanches 3-5 thick are possible on slopes over 35 degrees. Careful snowpack evaluation, cautious route-finding and conservative decision-making are essential.
  • Click HERE for the Hatcher Pass Avalanche Center advisory and HERE for recent snowpack observations.

The Bottom Line

The avalanche danger is MODERATE in the Turnagain Pass area. On slopes over 35 degrees and above ~1,500' there is the possibility for triggering a large (2-3') slab avalanche that breaks lower in the snowpack. The most suspect areas are on the South end of Turnagain Pass where the snowpack is shallower and there has been little traffic this season. In addition, watch for fresh shallow wind slabs to be formed, and possibly easy to trigger, due to an increase in winds along ridgelines. Last, cornice falls are still a concern along with glide avalanches. Below 1,000' the danger is LOW where surface crusts exist.

Girdwood Valley:  A shallower snowpack exists in the Girdwood Valley. Slab avalanches have the potential to be larger, over 3' thick, and break near the ground. 

Summit Lake:  Dangerous human triggered slab avalanche conditions persist in the Summit Lake zone. Check out the Saturday Summit Summary HERE


**The probability of triggering one of these large slabs is decreasing but the consequences remain high. This is more reason to be sure to carry your rescue gear and practice safe travel protocol - such as exposing one person at a time, grouping up in safe zones, having escape routes planned and watching your partners!  


Primary Concern

It has been just over 3 days since the tail end of the January 26th warm storm event added 2-3' of snow to the upper elevations. This event overloaded a variety of weak layers in the pre-existing snowpack and caused a widespread avalanche cycle in the region. The good news is the snowpack in the heart of Turnagain Pass is showing signs of adjusting to the load, the bad news is other areas are not. This can make for difficult snowpack assessment as the weak layers of concern (depth hoar, facets and buried surface hoar) are lurking anywhere from 2-4+ feet below the surface. Thicker snowpacks, as found at Turnagain Pass and on the North end of the Pass had a stronger snowpack to begin with and this has been a big factor in the area beginning to adjust quicker. This is opposed to the persisting unstable snowpack found South of Turnagain Pass and the Girdwood Valley.

In general - this is a high consequence but low probability situation. If choosing to ride or ski the steeper terrain, we recommend using safe travel protocol, especially exposing one person at a time and grouping up in safe zones. If a large slab is triggered it may run further than expected and wrap around terrain features taking out mid-slope relative safe zones. Since the weak layers in question are fairly deep, it will likely take finding a thin spot in the slab or a big trigger to initiate an avalanche.

A few points to consider today if visibility holds enough for travel to the high elevations:

  1. Obvious signs of instability may not be present (such as whumphing and shooting cracks)
  2. Large groups of people and/or snowmachines could initiate a failure and trigger an avalanche (or cornice fall)
  3. Cornice falls may trigger large slabs 
  4. Again, areas surrounding the main Turnagain Pass zone are the most suspect for these large slides, though Turnagain is not completely out of the woods.

Secondary Concern

With Several inches of soft settled powder on the surface, watch for winds today to take this and form soft wind slabs along ridgelines and potentially cross-load upper elevation gullies. These fresh slabs could be sensitive to human triggers and likely to be on the shallow end, up to a foot thick. Watching for recent wind loading, stiffer snow over softer snow, cracks that shoot out from you and performing quick hand pits are all good ways to assess whether you have found a wind slab. 

Winds have already impacted the Eddies ridge, to some degree, yesterday (photo: Andy Moderow)


Additional Concern

For those traveling in the Seattle Ridge area, there are a few glide cracks opening up above the flats along the Northern side facing the road. There are also a few cracks on the backside. Watching for these and limiting time underneath them is recommended.

Glide cracks on the North side of Seattle Ridge (photo: Andy Moderow)


Mountain Weather

Mostly sunny skies filled the region yesterday before clouds began filtering through later in the day. Ridgetop winds were light to moderate from the West before switching to Easterly mid-day and remaining light with gusts near 20mph. Temperatures warmed a few degrees, into the mid teens F at all elevations yesterday.

This morning, we are expecting clouds to begin filling in as a frontal boundary heads our way associated with a low-pressure system in the Bering. Snow, falling to sea level, is expected to begin later today with only 1-3" expected by this evening. Another 2-6" of snow is forecast for tonight into tomorrow morning (also falling to sea level). Ridgetop winds will bump up today into the 15-25mph range from the Southeast and bump up again into the 20-35mph range overnight. Temperatures should continue to climb to ~30F at sea level, the mid 20'sF at the higher elevations.

For Tuesday into Wednesday, the front is expected to stall and weaken, this will bring a chance for another few inches of snow and decreasing winds. Later in the week, high pressure builds bringing clear sky conditions with cooler temperatures.

*THANK YOU to whomever cleared the rime off the Seattle Ridge weather station yesterday!!!! 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 17  62 
Summit Lake (1400') 10  25 
Alyeska Mid (1700') 20   0 52 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 14  23 
Seattle Ridge(2400') 15  SE  13*  26*

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: Apr 11, 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: OpenWide swaths of open river in the Placer Valley. Travel with extreme caution!
Skookum Drainage: ClosedSKOOKUM DRAINAGE CLOSED TO MOTORIZED USE ON APRIL 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: ClosedClosed for the remainder of the 2017 season.
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

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
© 2017 Chugach National Forest Avalanche Information Center. All rights reserved.
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