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Avalanche Advisory

Turnagain Area Avalanche Advisory
Monday, April 2nd 2018 5:05 am by Wendy Wagner
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

A generally LOW avalanche danger exists in the core zone of Turnagain Pass, while areas on the periphery continue to trend from a MODERATE danger to a LOW danger. Triggering an old hard slab avalanche 2-4' thick is unlikely, but not out of the question. Areas of most concern are above 2,000' and in shallow snowpack zones such as Girdwood Valley and South of Turnagain Pass toward Johnson Pass and Summit Lake. Pay attention to afternoon warming and give cornices a wide berth. 

If you are headed South of Turnagain Pass check out the Summit snowpack and avalanche summary.


 Show the Complete North American Avalanche Danger Scale
1 Low Alpine / Above 2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
1 Low Treeline / 1,000'-2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Avalanche Problem 1

Deep Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

The sunny skies and high pressure that sit over our region will be present again today; clouds may move in tomorrow and a chance for snow exists on Wednesday. Despite the sunshine, chilly and breezy Northerly winds are likely to keep the sun from warming the snow surface too much today, limiting the chance for wet snow avalanches. What this means avalanche-wise is another day with no contributing factors to snowpack instability. We remain in a holding pattern of sorts as the chances for triggering an old hard slab avalanche are becoming more unlikely as time goes on.

The current snowpack has a poor structure with many weak layers that sit 2-4' below the surface. These layers are composed of facets and buried surface hoar. The slab on top is hard and varies in thickness due to prior wind effect. The snow surface has been beat up by wind and sun over the past three weeks. Although the weak layers continue to adjust and the slab on top is losing its ability to propagate, we are still concerned someone could find just the wrong spot on just the wrong slope and trigger a dangerous avalanche. Places most suspect are thin snowpack zones such as the Girdwood Valley and the South end of Turnagain Pass towards Johnson Pass, Lynx Creek and Summit Lake. Additionally, North and Easterly slopes in general have a thinner pack making them more suspect. Trigger points in this situation are often in thin areas near rocks or in scoured areas along ridges. As always, practice safe travel habits, expose one person at a time and minimize exposure in avalanche terrain. 

Although winds are likely to limit surface warming by the sun, keep this on your radar in the afternoon. If the snow heats up enough to become wet and punchy, it's time to move to another aspect. Photos below are from Portage Valley on Saturday. This close up view on the right is a solar aspect of Maynard Mtn on the North side of Portage Lake. This slope is one of the first to have natural wet avalanches on sunny warm days. 

 

 

Note the snowfall during March in the chart below. One large storm right before Spring Break that brought 2-3 feet of snow to the region. Since then, only a few inches has fallen and since March 20th, no snow has fallen. 


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Additional Concern

Cornice

Watch out for cornices along ridgelines. It's that time of year where cornices will begin to slowly warm during daytime heating, making them easier to break off. As always, give cornices plenty of space and limit exposure underneath them. 


Mountain Weather

Yesterday sunny skies prevailed again over the region. Ridgetop winds were light (5-10mph) with gusts in the 20's mph from the Northwest. During the day, temperatures warmed to the low 40'sF at sea level and to 30F along ridgetops. Overnight, temperatures have dropped to the teens to the low 20's at sea level and similar along ridgelines.

Today, Monday, we can expect clear skies again. Ridgetop winds may bump up slightly from the North to the 10-15mph. Temperatures should climb at sea level to near 40F again today and to near 30F along ridgelines. 

For Tuesday, clouds may move in ahead of a low-pressure that looks to move into our region from the East on Wednesday. This may also bring a chance for light snowfall on Wednesday. Stay tuned!

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 31  75 
Summit Lake (1400') 30  30 
Alyeska Mid (1700') 31  70

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 24    NW  23 
Seattle Ridge(2400') 29   NW 32 

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: Dec 01, 2018 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed
Placer River: ClosedClosed
Skookum Drainage: ClosedClosed
Turnagain Pass: ClosedClosed November 21 due to inadequate snow conditions. #hopeforsnow
Twentymile: ClosedClosed
Seward District
Carter Lake: ClosedClosed
Lost Lake Trail: ClosedClosed
Primrose Trail: ClosedClosed
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: ClosedClosed
South Fork Snow River Corridor: ClosedClosed
Summit Lake: ClosedClosed

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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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