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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Sunday, January 4th 2015
Created: Jan 4th 6:13 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.
0 NO RATING Below Treeline / Below 1,000'
 Show the Complete North American Avalanche Danger Scale
Special Announcement

Upcoming Events:
      
- We have rescheduled the CNFAIC Avalanche Rescue Workshop for January 18th due to minimal snow coverage at the parking lot level in Turnagain Pass. 

- Join us for our final Fireside Chat this Thursday, January 8th, in Anchorage! Topic: Mountain Weather and Snowpack. We will be taking a close look at the current state of the snowpack at Turnagain Pass along with a look into "when is it going to snow?".

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If you are getting out in the backcountry to enjoy the next few clear sky days  - remember you can participate in this very interesting research project: "Understanding Travel Behavior in Avalanche Terrain: A Crowdsourced Approach".  Researchers from Montana State University are looking for data sets worldwide and we can help provide some valuable AK data!


The Bottom Line

The avalanche danger remains MODERATE in Alpine terrain (>2,500') on steep slopes for hard slab avalanches breaking 1-3' deep. Although an avalanche will be difficult to trigger, the potential is there that one could bury or injure a person. 

At the treeline elevations (1,000-2,500') the danger is LOW where triggering an avalanche is unlikely.


Primary Concern

As we roll into a several day period of high pressure and clear skies, don't forget what is lurking below the surface. Roughly 2' down (give or take a foot) are persistent weak layers that vary with region. Turnagain Pass is plagued with mainly buried surface hoar and in lower snowpack zones, such as the West side of Girdwood Valley and Summit Lake, varying degrees of a facet/crust combination also exist. Although the slab on top is very hard and dense, making it difficult for a person's weight to impact these layers, they are still there, not buried all that deep and continue to show signs of reactivity in pits. 

I was with an Avalanche Level 2 Refresher course yesterday and we dug several pits in the lower Alpine zone (~3000') focusing on the buried surface hoar. Test results were exactly what we saw a week ago - high strength (hard to trigger an avalanche) and high propagation propensity (if an avalanche is triggered, it has potential to propagate across an entire slope). Although time is on our side and the buried surface hoar has adjusted to its current load, it still doesn't buy a ton of confidence.

A few things to remember with this type of Avalanche Problem:

  • Absence of red flags until it's too late (whoomphing, collapsing, cracking)
  • Trigger points are often where the snowpack is thin (around rocks and steep rollovers)
  • Make sure your safe zones are truly safe, hard slabs can propagate wider than you may expect
  • Expose only one person at a time


Photos: Buried surface hoar that is laying 14-16" deep at 3,100' on Sunburst's SW face (Ryan Davis).

Left photo, standing upright on the bottom of the slab.                  Right photo, laying on a 2mm grid (5-8mm in size)
  


Secondary Concern

Very hard and supportable wind slabs litter the mountainsides above treeline. These are generally 6-12" thick and fairly well locked into place in many areas. However, there is still a possibility of triggering one in very steep and rocky terrain. Chances also go up if the slab is unsupported from below (i.e., is sitting above a cliff, steep rollover or a steep gully sidewall).

This also paints a picture of the current surface conditions in exposed, above treeline zones - hard and slick. Where stiff wind slabs are not present, scoured snow, rocks and anti-tracks are. Sounds a bit dire, yes, but there is fun riding to be had in sheltered areas in the trees as well as terrain depressions and the like.


Mountain Weather

Mostly clear skies and light North winds greeted backcountry travelers yesterday. Temperatures were in the upper teens in valley bottoms and ~20F on the ridgetops. The last measureable precipitation was December 30th (the end of the very windy late December storm). 

Today, clear skies are on tap once again as a blocking high pressure has set in over mainland Alaska. A slight bump in Northerly winds (up to 10-15mph) are expected on the ridgetops. Temperatures are inverted this morning with valley bottoms in the single digits to low teens and the high teens to 20F on the ridgetops. We should see little warming through the day.

Our weather the next several days will be dominated by this blocking high pressure. Later in the week, there is a chance it could break down in the Southcentral coastal zones bringing some clouds and a chance for snow flurries. You can bet we will be watching the longer range weather models for the next storm.

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 21  34 
Summit Lake (1400') 16 
Alyeska Mid (1700') 19  0 25 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 20  NW  13 
Seattle Ridge(2400') 19  Variable  10

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 16, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedThanks all for a safe and fun season on the Chugach NF! Stay tuned for the 2017/18 season. #playsafe #snowtosealevel
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail will be open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
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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