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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Tuesday, February 24th 2015
Created: Feb 24th 6:02 am
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
3 Considerable Treeline / 1,000'-2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
0 NO RATING Below Treeline / Below 1,000'
 Show the Complete North American Avalanche Danger Scale
Special Announcement

If you haven't heard - the first annual SNOWBALL is around the corner!! A "more formal than normal" night of music, door prizes, raffle and fun is on the schedule at the Taproot this Friday. Please join the Friends of the Chugach National Forest Avalanche Information Center and Alaska Avalanche School in an effort to support local avalanche education and information!


The Bottom Line

The avalanche danger remains CONSIDERABLE on all aspects and slopes above 2,000'. Wet slab avalanches up to a foot thick will be possible to trigger in the short elevation band from 2,000'-~2,500'. Dry slabs, 1-3+' thick, will also be possible to trigger above roughly 2,500'. On top of these slab avalanche problems, daytime warming and solar radiation may induce wet loose slides on steep Southerly slopes. 

NOTE:
Although natural avalanche activity is not expected today and human triggered avalanches are only possible as opposed to likely, which is the definition of a MODERATE avalanche danger rating, today's rating is based on the "Travel Advice" column of the danger scale - stated above in orange. We have very little information for Turnagain Pass and the surrounding mountains. As we head into a relatively clear sky period and travel into the backcountry and the upper elevations is possible, know that there is a layer of weak faceted snow under a variable slab 1-3+' thick. Careful snowpack evaluation, cautious route finding and conservative decision-making will be key for a safe outing. 

A fun day skiing or riding can be had in the dry snow by sticking to slopes 35 degrees or less and avoiding steep rollovers on the ascent through the mid-elevation wet and crusty snow.


Primary Concern

Following in step with our unprecedented warm winter, during the past several days we have seen rain falling on snow up to 2,000', and as high as 3,000' in places. Water amounts have accumulated to ~.7" on Turnagain Pass and up to 2" in the Girdwood Valley since Saturday. Not only has this been raising the snow line (which is currently around 1,500') but it has more importantly induced a mini wet slab cycle in this small elevation band. Technically, warm temperatures and sunshine has helped to tip the balance for some of these wet slabs after the rain, but regardless, there is a poor snowpack structure in the top 1-2' and this is why we are seeing wet slabs. Below are some shallow slabs seen yesterday in the Portage Valley - these are similar to the shallow slabs on Seattle Ridge two days ago

For today, skies have been clearing the temperature dropping which will start freezing the pack from the surface down and decrease the wet slab potential. But, only a shallow re-freeze on the surface should not be mistaken for good stability. Sometimes a shallow re-freeze can act to strengthen the slab enough to increase triggering potential before it does indeed freeze enough to be safe; something to keep in mind when moving through the mid-elevations to get to the drier snow above.

Portage Valley shallow wet slabs likely from Sunday 2/22 (Maynard Mtn, West facing ~2,000').


Secondary Concern

In the dry snow, which begins roughly just above 2,500', we continue to be concerned with the well documented layer of faceted snow that sits under a slab 1-3+' thick. The slab is highly variable due to the extreme winds seen a week ago. From the little information we have been able to gather, high variability does exist in the slab depth as well as the weak layer depth and strength. This variability can be helpful in breaking up the slab/weak layer combo and minimize the ability for an avalanche to propagate across entire slopes. However, a 3' slab is nothing to mess with even if it does just release in a pocket and not over an entire slope. 

If you are getting out in search of dry snow today:

  • Watch for RED FLAGS - collapsing (whoomphing) will be most likely

  • Be aware this set-up is the type where NO Red Flags may be present until a slope avalanches

  • Stability tests may not be representative due to the variability of the slab (and possibly the weak layer)

  • Practice safe travel protocol!!! Exposing only one person at a time, watch your partners and have an escape route planned if choosing to enter terrain over 35 degrees

Mountain Weather

Partly cloudy skies, some sunshine and intermittent rain showers covered much of the region yesterday. Around 0.2" of rain fell below 2,000' with a dusting of new snow above this. Ridgetop winds were 5-10mph from the Southwest while temperatures were in the upper 30's F at 1,000' and in the upper 20's F on the Ridgetops.

Overnight, skies have continued to clear and temperatures have cooled slightly at each station (ridgetop as well as valley bottom). Valley fog is likely today with partly sunny skies above. Temperatures should warm back up to the mid 30's at 1,000' and the upper 20's on the ridgetops and feel quite warm in areas with sunshine. Ridgetops winds are expected to be in the 5-10mph from the East. 

We look to remain between storms with mostly sunny skies and light winds through Friday; a low pressure does brush to our South on Wednesday, which should only bring some high clouds and moderate East winds. The weather models are showing our next shot of precipitation on Saturday with another dose of warm, wet and windy weather.

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 32  rain  0.1  40 
Summit Lake (1400') 30  rain  0.1 
Alyeska Mid (1700') 33  rain  0.17  22 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 26  N/A  N/A   N/A  
Seattle Ridge(2400') 27  N/A   18 

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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