Avalanche Advisory

Turnagain Area Avalanche Advisory
Friday, January 17th 2014 7:00 am by John Fitzgerald
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche hazard is HIGH at all elevations.  Large natural avalanches are likely today.  Rain & snow along with warm temperatures and high winds will make for very dangerous conditions in the backcountry.  Travel in or near avalanche terrain is NOT recommended today.

All of the concerns listed below deserve equal weight in terms of both likelihood and consequences.

 Show the Complete North American Avalanche Danger Scale
4 High Alpine / Above 2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4 High Treeline / 1,000'-2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4 High Below Treeline / Below 1,000' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
Special Announcement

There will be intermittent closures today on the Seward Highway for avalanche hazard reduction work between Girdwood and Seward near mileposts 99, 97, 87, 44, 37, 21.  Motorists should expect delays of up to 45 minutes between 10:00 AM and 3:00 PM.

Updates will be posted on the 511 system.

Avalanche Problem 1

The already tenuous snowpack is receiving a significant shock to its system.  Rain began falling up to 2,000’ overnight.  Snow that has fallen since mid December has formed into slabs up to 3 feet in depth.  That slab is now losing strength.  As that slab loses strength it becomes much more likely for weak layers near the ground to awaken and release large avalanches.  Expect entire slopes to avalanche.

Wet slab and wet loose avalanches are possible up to 3,000' in elevation today.

Avalanche Problem 2

Heavy wet snow combined with high winds in the upper elevations will create very unstable conditions within the new snow today.  Freshly formed slabs up to 2 feet in depth will likely avalanche on their own.  High winds will also help to build slabs in areas that don't normally see much wind (e.g. below treeline and well below typical starting zones).  These slabs have the potential to step down to older weak layers near the ground.  Expect avalanches to pull out across large areas and run long distances.

Additional Concern

Weak layers that make up the bottom of the snowpack proved to be reactive yesterday.  Both natural and remotely triggered avalanches were observed.  Even if we took today’s weather out of the equation we would still have dangerous avalanche conditions.  Given today’s weather, the likelihood of triggering an avalanche in these deeper weak layers is rapidly on the rise.  Warm temperatures and rain up to 2,000 feet will help to activate these layers.  Dangerous slabs up to 3 feet in depth are likely to take out large areas today.

Mountain Weather

Red flags abound in the weather category today.

Temperatures (F) are first, with current temps (6am):
Center Ridge SNOTEL @ 1,880': 35
Seattle Ridge @ 2,400’: 30
Sunburst @ 3,812’: 28

Center Ridge had a high overnight reading of 40 deg F.  This is a 10 degree rise in 12 hours.

It is currently raining at Center Ridge with .4” of water over the past 8 hours, with slightly higher amounts in the Girdwood Valley (.5" of H2O).  This equates to roughly 5” of new snow at ridge tops.  This by itself is a modest amount of snowfall in starting zones.  However, let’s take a look at winds.

Sunburst averaging 62 mph out of the East.  Gust to 105 mph.
Seattle averaging 48 mph out of the ESE.  Gust to 82 mph.

Precipitation, temperature and winds are currently combining to create very unstable conditions.

Today expect as much as 12” of new snow, with 2” of snow water equivalent.  Freezing level will climb up to ridge top elevation (3,000’).  Ridge top winds will be strong all day, in the 65-70 mph range.

Winds and precipitation should taper off on Saturday.  The pattern will remain active (continuation of precip) through the weekend and into the early part of next week.

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 06, 2019 )

Glacier District
Johnson Pass: ClosedClosed as of 4.3.19
Placer River: ClosedClosed as of 3.20.19 due to lack of snow.
Skookum Drainage: ClosedPlacer access closed as of 3.20.19 due to lack of snow.
Turnagain Pass: ClosedClosed as of 5/6. Thanks for a great season all, see you next winter!
Twentymile: ClosedClosed as of 3.20.19 due to lack of snow.
Seward District
Carter Lake: Closed
Lost Lake Trail: ClosedClosed as of 3.22.19 due to lack of snow
Primrose Trail: ClosedClosed as of 4.3.19 due to lack of snow
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: ClosedClose as of 5.1.2019
South Fork Snow River Corridor: ClosedClosed as of 3.20.19 due to lack of snow.
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.

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