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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Wednesday, March 2nd 2016
Created: Mar 2nd 5:18 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
Alaska Mountaineering and Hiking
The Bottom Line

The avalanche danger is MODERATE in the Turnagain Pass area today for slab avalanches, cornice falls and glide avalanches. It will be possible for people/snowmachines to trigger slabs 1-2' thick at elevations above 1,000'. These are most likely on the steep sunlit slopes, more than 35 degrees. Cornice falls are possible as well, and could trigger slabs below. Last, glide avalanches remain a concern at the mid-elevations. Easing into terrain will be key. Pay close attention to Red Flags: warming by the sun, recent avalanches, 'whumphing', and cracking in the snow.

*There is little information for areas South of the Pass, such as Silvertip, Summit Lake and Johnson Pass zones. More reason for a conservative mind-set. 

**Remember a MODERATE danger means human triggered avalanches are possible:


Primary Concern

After a 10-day storm deposited between 10 and 15 feet of snow at the upper elevations, yesterday was our first day with no precipitation and today will be our first clear sky day. Many of us have been eagerly awaiting this window of high pressure to travel places other than the low angle trees and flats. After two days of snowpack analysis, one day on Seattle Ridge and one day on Tincan, we have few data points to pull from. However, from these we have found both stable and unstable results. The stable results were from Tincan (more on that HERE) and the unstable result was from Seattle Ridge (that can be seen HERE). That said, we should head into today with a conservative approach. Although large connected avalanches are not expected, pockets of wind slab and old lingering storm slabs could be triggered. Keep in mind, these pockets can be large enough to ruin your day.

SUNSHINE:
Warming by the sun is expected to help destabilize slabs that remain tippped on the balance. That makes two trigger mechanisms for lingering slabs and cornices, sun and people. Keep an eye out for warming snow surfaces and roller balling. These are signs the snowpack properties are changing and triggering an avalanche more likely.

Wind Slabs: Strong winds Monday night have formed wind slabs and wind crusts along ridgelines and in exposed areas. 

Storm Slabs: Lingering storm slabs are possible where fluctuations during the storm created layers of crusts, strong snow and weak snow. This is what Graham found on Seattle Ridge on Monday. These storm slabs are most likely to be found at the mid-elevations.

Sluffs: Sun induced loose snow avalanches are possible. These will likely be damp heavy snow and could push you around on steep sunny slopes.

A CALL FOR OBSERVATIONS:
We want to hear what you are seeing!! Please pass on photos/videos/a few sentences of what you see today/tomorrow. We are trying to map out the post-storm snowpack.


Secondary Concern

Cornice fall may one of the larger hazards today with sunshine acting to weaken these already tenuous bombs. Cornices right now are LARGE - some bigger than a semi-truck. Limiting time spend under these is key. With amount of snow from the last storm, discerning how far back from the ridge you should travel could be difficult, err on the safest side possible as they really can break much farther back than expected!

Photo: Cornice fall on the Tincan Ridge (CFR). This large cornice fell just after the end of the storm cycle, possibly Tuesday. It triggered a wind slab below and ran around 700' down the slope out of view. This is one the smaller cornices seen in the area.


Additional Concern

Glide cracks are moving and coming out of hiding after they were covered by wind and snow during the storm cycle. Although it has been several days since the last glide crack we know of released and avalanched, they are still on the move. Limiting time spend under cracks is crucial, as they will mow anything down in their path if one does release.


Mountain Weather

Yesterday, the mountains surrounding Turnagain Pass saw overcast skies with some sunshine breaking through. Over the past 24-hours there has been no precipitation, winds have been light out of the East on the ridgelines and temperatures have been mild (~32F at 1,000' and in the low to mid 20's at 3,500'). Temperatures in valley bottoms have cooled overnight to the low 20'sF.

Today, we are scheduled for our first sunny day in just about two weeks; yet, this could be in conjunction with some valley fog. Winds are forecast to be light, 5-10mph out of the East along the ridgelines. Temperatures should be warm, up to 30F at 3,000' and 35F at 1,000'.

Thursday another nice and sunny day is on tap before clouds begin to move in Friday ahead of a possible weekend storm system. Stay tuned.

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 28  143 
Summit Lake (1400') 29  42 
Alyeska Mid (1700') 30  106 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 24  NE  31 
Seattle Ridge(2400') 23 

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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