CNFAIC LogoCNFAIC Logo

Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Tuesday, January 13th 2015
Created: Jan 13th 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.
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.
0 NO RATING Below Treeline / Below 1,000'
 Show the Complete North American Avalanche Danger Scale
The Bottom Line

A MODERATE avalanche danger exists at all elevations in the backcountry. Naturally occurring glide avalanches and human triggered wet loose avalanches will be possible in the treeline elevation band (1,000'-2,500'). Above treeline, in the Alpine, human triggered fresh wind slab avalanches 8-16" thick will be possible on wind loaded slopes.


Primary Concern

Another warm, wet and windy storm is impacting the Eastern Turnagain Arm region once again. This system moved in yesterday afternoon and will be exiting today. So far we have seen just under an inch of rain up to 2,500' with heavy wet snow above this. The rain has likely melted most surface crusts up to 2,500', and possibly higher, and will continue to saturate the snowpack. This will create wet loose avalanche potential along with an increased glide avalanche potential.

Since the pack has already adjusted to rain up to 2,500' from the last storm, it is not prime to produce significant natural wet avalanche activity. Yet, at the upper elevaitons we may see some shallow wet loose avalanches in the new snow as temperature climb slightly today. That said, human triggered wet loose snow avalanche will be possible on steep slopes where loose, unconsolidated and soggy snow exists. On sustained steep slopes these could be quite large. Avoiding steep terrain with unsupportable wet snow is recommended. 

Glide Avalanches:
We are currently in a "glide cycle" of sorts. We have seen widespread glide crack development through Turnagain Pass and Girdwood Valley during the past 3 days. Only a handful of these cracks have actually avalanched. Check out the comparison photo below put together by Heather Thamm. This shows that not all glide avalanches are preceded by a slowly opening crack. Something to keep in mind if you are headed out in the backcountry. This can make avoiding being under a glide avalanche more tricky, but most of the time they do have glide cracks present which are easy to recognize.

 


Secondary Concern

While it has been raining up to 2,500', it has been snowing above this. I think it is safe to say that around 5-8" of heavy to medium density snow exists and covers essentially the top 500-1,000' or so of the ridgelines around Turnagain Pass. The new snow has come in with strong Easterly winds which has likely built wind slabs up to 8-16" in depth. Another 2-4" of snow is expected with moderate Easterly winds today which, if this is the case, add to the slabs from the past 24-hours. These will be sitting on a hard pre-existing crust and bonding of the new slabs to the older crust is uncertain. However, I'd expect with the warm temperatures, that these slabs should settle out rather quickly and be somewhat stubborn to trigger. 

If you are headed out in search of new snow at the high elevations, watching for red flags (recent avalanches, collapsing and cracking in the new snow) will be essential. Quick hand pits are an additional great way to see how the new snow is bonding.


Mountain Weather

Light rain spread over our area yesterday with a more intense precipitation period overnight as a warm storm is slowly exiting the region. A total of 0.9" of water has accumulated at the Center Ridge Snotel station as of this morning while Girdwood Valley has seen 0.7" and Summit Lake recording no measureable precipitation. The rain/snow line was up to 2,500' with temperatures close to 30F on the ridgetops and the upper 30's F below treeline. Winds have been strong from the East, averaging 33mph with gusts over 70mph at the Sunburst weather station.

Today, 0.3-0.5" of rain is expected to continue up to 2,500', possibly higher, with 2-4" of heavy snow above this. Temperatures should remain near 30F on the ridgetops and in the upper 30's at and below treeline. Ridgetop winds will continue from an Easterly direction in the 20-25mph range.

As we head into the remainder of the week, a series of warm low pressure systems continue to spin in the Gulf bringing intermittent rain showers. The rain/snow line looks to remain near 2,500' (or higher) through Thursday. Friday, cooler air does look to become mixed in and we may see the rain/snow line drop to 1,500' or so for the weekend.

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 36  0.9  29 
Summit Lake (1400') 37 
Alyeska Mid (1700') 36 0.7  21.5 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 29  33  74 
Seattle Ridge(2400') 30  NE  14  42

 

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: Nov 18, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedOnly a few inches of snow sits at the motorized lot, not enough to open for snowmachining at this time. Updated Nov. 18, 2017
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail is expected to open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
Summit Lake: Closed

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.
FCNFAIC