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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Sunday, January 3rd 2016
Created: Jan 3rd 6:05 am
4 High Alpine / Above 2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
3 Considerable Treeline / 1,000'-2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
2 Moderate Below Treeline / Below 1,000' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
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Special Announcement

We are sad to report an avalanche fatality occurred yesterday in Hatcher Pass involving one person on a snowmachine on the Willow side of the Pass. Right now information is limited; check out Hatcher Pass Avalanche Center website and read the most recent article HERE on Alaska Dispatch News. 

OUTSIDE OF CNFAIC ADVISORY ZONE:

*Over the weekend natural and human triggered avalanches have occurred near Anchorage and Eagle River in the Front Range. Strong winds and snowfall are creating dangerous avalanche conditions throughout the region. Keep in mind summer trails can pass through avalanche paths such as the Flattop trail, where an avalanche occured on Friday. Check out several recent Front Range observations HERE.


The Bottom Line

Over the last two days 3 feet of new snow and strong winds have rapidly loaded the mountains surrounding Turnagain Pass and created a HIGH avalanche danger in the Alpine zones (above 2,500'). CONSIDERABLE avalanche danger exists at Treeline (1,000'-2,500') where triggering a wind slab 2-6' thick is possible today on steep wind-loaded slopes. Sticking to mellow terrain (off and out from under slopes 35 degrees and steeper) and avoiding avalanche terrain is recommended. In the Treeline zones, careful snowpack assessment and conservative route-finding will be necessary. A MODERATE danger exists in the runout zones below 1,000' where debris from an avalanche above could reach.   

*At Summit Lake 2 feet of new snow has created dangerous avalanche conditions. Yesterday a snowboarder triggered a 3’ slab on Tenderfoot, and luckily was not buried or injured. Don't forget to check the weekly summary for Summit Lake (on the Kenai). This summary is produced on Saturday mornings at 7am.

 


Primary Concern

A strong Southerly flow will continue to bring us showery conditions today; 3-5” of new snow is expected. Easterly ridgetop winds 20-30mph will continue to transport snow in the upper elevations and load leeward aspects. This is in addition to 28”of new snow that has fallen in the last two days, a total of almost 9’ of snow since Christmas. Rain/snow line has fluctuated between 1500’ to 800’ this weekend causing wet saturated snowpack below Treeline. Wind slabs in the new snow could be as thick as 6' in places. 

If you are thinking of heading to Turnagain Pass today, keep in mind the 'rapid loading' is a Red flag and warrants extreme caution. Avoid all avalanche terrain including putting yourself under steep slopes where a natural avalanche from above could run into flat terrain.

Many different avalanches are possible today:

1) Wind slab: Triggering a wind slab 2-6’ thick is likely on steep wind loaded slopes. Winds are forecast to remain from the East in the 20mph range. If this is the case, fresh and sensitive wind slabs will remain through the day. 

2) Cornices: With such strong winds and warm snow at the ridgetops, we can expect cornices to be tender! Not only can these trigger an avalanche below, but may also trigger a slide breaking deeper in the snowpack - creating a very large avalanche. 

3) Wet loose avalanches: Rain and wet snow has saturated the snowpack below 1500’ in Turnagain (up to 2000’ in Girdwood and Portage.) This is more of a concern in areas with terrain traps and in steep channeled terrain where an avalanche from above will be impossible to escape. Cooler temps today will be helping this part of the snowpack drain.

Be aware that plow drivers are working hard to keep Turnagain Pass clear of snow. With heavy wet snowfall like yesterday many of the parking areas may not be plowed. Please try to park in places that allow the plows to continue working. 


Secondary Concern

Yesterday in Summit Lake a snowboarder triggered an avalanche on Tenderfoot in an area many perceive as safe terrain. In the last two days Summit Lake has received 2’ of new snow, which is sitting on several different layers of weak snow including buried surface hoar. Human triggered slabs 3-4’ deep are likely in the Summit Lake area today and may be triggered on slope angles less than 30°. Obvious signs like wumpfing should not be ignored.

A weak layer sitting on a hard bed surface is buried under 5’ of settled snow. Many large avalanches have been observed naturally in channeled terrain along Turnagain Arm and Portage this weekend, but due to poor visibility it is unknown if avalanches have occurred on these older layers. Periods of rain have saturated areas of the snowpack below 2000’. Several large avalanches (D3’s) were triggered yesterday morning with artillery at Alyeska. One of these large avalanches triggered a large wet slab at 1800’ likely on the Thanksgiving crust bed surface. Snow pit tests at Tincan have demonstrated good stability this weekend, but due to limited information we don’t want to make any assumptions. Buried surface hoar is also lurking in the snowpack.

The bottom line is poor structure exists in the snowpack and a 10 day loading events (snow, rain and wind) have created a high consequence avalanche problem. More time and stable weather conditions are needed before it will be safe to go into avalanche terrain. 

 

 


Mountain Weather

Yesterday Turnagain Pass another 8” of new snow in addition to the 20” the day before. Winds were in the 20’s mph gusting to into the 40’s mph. Rain was observed below 800’ in Portage and Girdwood.

Overnight winds have decreased and precipitation stopped.  Temperatures have cooled slightly dipping below 32F at the road level at Turnagain Pass.

Today Easterly ridgetop winds are expected to increase back to the 20-30 mph range. Light snow should start falling this morning into the afternoon, but only a few inches are expected. Temps look to be cooling slightly which means rain/snow line may be as low as 600’.

Heavy precipitation is expected late tonight through Monday with similar temperatures as today.



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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 30   0.8 90 
Summit Lake (1400') 31  0.7  32 
Alyeska Mid (1700') 32  2  0.31 64 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 23  NE  20  43 
Seattle Ridge(2400') 26  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: Apr 28, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: ClosedSKOOKUM DRAINAGE CLOSED TO MOTORIZED USE ON APRIL 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: OpenOpen thru May 14th.
Twentymile: Closed
Seward District
Carter Lake: OpenClosed May 1.
Lost Lake Trail: OpenClosed May 1.
Primrose Trail: OpenClosed May 1.
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: OpenClosed May 1.
South Fork Snow River Corridor: OpenClosed May 1.
Summit Lake: OpenClosed May 1.

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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