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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Thursday, February 9th 2017
Created: Feb 9th 6:01 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
Key Bank
Special Announcement

Many areas around Southcentral, Alaska including the Southern Kenai Mountains, Seward, Snug Harbor and Lost LakeAnchorage Front RangeHatcher Pass continue to have an unstable snowpack. Human triggered large avalanches, breaking near the ground, are possible. Please see links above for recent activity. Careful snowpack evaluation and cautious route-finding is essential. 

Mark your calendars: This Saturday CNFAIC and the Anchorage Snowmobile Club will be hosting a FREE Avalanche Rescue Workshop at Turnagain Pass, 11am -12:30pm in the Motorized parking lot. We will focus on practicing with your avalanche beacon, probe and shovel. This workshop is open to everyone and anyone, novices and experts, that recreate in avalanche terrain – snowmachiners, skiers, snowboarders, etc… Click HERE for more details. 

 

 

 


The Bottom Line

The avalanche danger above 1500’ in Turnagain Pass remains MODERATE due to a poor snowpack structure where triggering a large slab avalanche (2’-5’ thick) that breaks near the ground is possible. This is a low probability, but high consequence situation and it is critical that safe travel protocols are executed and avalanche rescue gear is carried. This means only one person on a slope at a time - in the event an avalanche is triggered, there are people capable of rescue. Additionally, there are some normal caution problems to keep an eye out for today, these are: shallow fresh wind slabs, sluffs in steep terrain and cornice breaks. 

Below 1500’ the avalanche danger is LOW where triggering an avalanche is unlikely. 

Summit Lake and Girdwood:  A poor snowpack structure exists in these areas as well and human triggered avalanches breaking near the ground are possible. Make sure and check the Saturday Summit Summary HERE.


Primary Concern

It has been 6 days since two separate snowmachine triggered avalanches occurred in Turnagain Pass zone, one in Seattle Creek and the other in Lynx Creek. Sunny weather this week has allowed many people to venture far and wide, testing a lot of terrain without incident. The likelihood for someone to find and trigger a large slab is decreasing as the snowpack adjusts, but the poor snowpack structure remains and the consequences are scary. For example the avalanche in Lynx Creek had a crown that was 1000’ wide and ran 1500’ into a large terrain trap. The slab was 1-4’ thick and was sitting on weak faceted snow near the ground. Both near miss avalanche accidents last week were triggered in thinner areas of the snowpack, on slopes that already had tracks on them. The tricky part about this particular avalanche problem is that it is very difficult to assess. Obvious signs like whumpfing and shooting cracks are unlikely and stability tests may not be reactive. Just because a slope has tracks on it does not mean it is safe. Likely places to trigger a deep persistent slab will be near rocks or in scoured zones. Likely triggers are large: snowmachines, groups of people or cornice falls. Identify and avoid terrain traps (like large gullies,) and always practice safe travel protocol, by only exposing one person at a time on steep slopes. 

Click HERE to read the detailed near miss report about the Seattle Creek avalanche where one snowmachiner was fully buried, and a quick rescue by his partners saved his life. Click HERE for the initial details about the Lynx Creek avalanche where luckily no one was caught. Stay tuned as we will be posting more info about this avalanche soon.

A photo of the crown on a NE aspect of Seattle Ridge avalanche near the Headwall. Photo taken 2/6/17 by Wendy Wagner

  

 


Secondary Concern

Wind slabs: Light flurries today combined with Easterly ridge top winds 10-20mph are expected and may form small isolated wind slabs on leeward features. There is also up to 8” of older loose snow available for transport. These wind slabs could from on a hard sun crust on Southern aspect and may be extra tender. Keep an eye out for blowing snow and pay attention to which slopes may be more loaded. Avoid pillowed or drifted snow or areas with stiff snow over soft snow on high consequence terrain.

Loose snow: With 4-8" of loose snow on the surface over a dense base and possibly a few inches of light dry snow today, watch your sluff. 

Sun: It's that time of year again. Although the sun is not expected today, should it appear, it has the potential to weaken the surface snow and make wind slabs and loose snow easier to trigger. 

Sun crust found on a SE aspect of Tincan early this week. Photo courtesy of Brooke Edwards


Additional Concern

This weekend cornice cracks were reported along the back bowls of Seattle Ridge making some of these cornices extra sketchy. A few chunks have been triggered this week. Also these features can be difficult to see in poor visibility. Remember these unpredictable hazards can break farther back onto a ridge than expected and have the potential to trigger an avalanche on the slope below. Give cornices extra space and avoid being under them. 

 


Mountain Weather

Yesterday clear skies became overcast by early afternoon and winds were light from the East, 5-15mph. Temperatures averaged between 15F to 20F at all elevations. Snow flurries have been observed this morning at the Turnagain Pass DOT web cam, but no measurable amount has accumulated.

Today expect light snow flurries throughout the day, 1-3” by this evening. Southeast ridge top winds are expected to be in the 10-20mph range and temperature are forecasted to drop throughout the day into the single digits (F) by this evening. A similar pattern is expected through tomorrow.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 17  49 
Summit Lake (1400') 17  trace  .1  24 
Alyeska Mid (1700') 21  45 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 15  13 
Seattle Ridge(2400') 16  16 

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
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