Avalanche Advisory

Turnagain Area Avalanche Advisory
Monday, December 23rd 2013 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 MODERATE today above and below treeline.  It will be possible for large triggers such as snowmachines or groups of people to trigger slabs up to 2 feet in depth on steep terrain today.  Isolated pockets of newly formed wind slabs will also be an issue to contend with in higher elevation terrain with an Easterly component.

 Show the Complete North American Avalanche Danger Scale
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.
2 Moderate Below Treeline / Below 1,000' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1

Over the past several weeks snowfall has come in small doses.  This has helped to slowly build a slab on top of a generally weak foundation.  Due to the gradual nature of these loading events, avalanche activity has been spotty in nature.  Yesterday we received reports of two human triggered avalanches in mid elevation terrain (one report HERE).  We have been experiencing collapsing for several days in a row at all elevations but not widespread avalanche activity.  What this boils down to is that we are in the “gray zone” of MODERATE avalanche hazard.  The snowpack structure is poor in most areas-there is a slab (up to 24”) sitting on weak snow near the ground.  But there has not been quite enough of a load to create instability that is obvious and easy to predict.

Because of this, it is worth continuing to treat slopes above 35 degrees with suspicion.  Cooler temperatures today will likely make the snow less reactive but the potential still exists for skiers or snowmachiners to trigger slabs up to 2 feet in depth.  Exposing only one person at a time to steep terrain, spacing out across slopes and communicating your plan within your group will help to minimize your exposure to avalanche hazard.     

Avalanche Problem 2

Winds overnight kicked up into the 30-40mph range (with gusts to 61mph) out of the Northwest on Seattle Ridge.  The winds at Sunburst have been significantly less (5mph average).  Because of this, these slabs will be scattered about in pockets on primarily East facing terrain. Fresh new wind slabs will exist in pockets and will be most sensitive on steep slopes above treeline.  Avoid snow in starting zones or above cross loaded gullies that have a smooth, rounded look to it. With this new load the potential also exists for smaller wind slabs to pull out deeper weak layers in the snowpack.

Mountain Weather

In the past 24 hours the mountains around Eastern Turnagain Arm have picked up a trace of new snow.  Temperatures have been on the decline with daytime averages yesterday in the mid twenties F and current ridge top temps in the single digits to teens F.  Winds at the Seattle Ridge Station over the past 12 hours have averaged 30mph out of the NW.

A small ridge of high pressure will build over the area today, bringing clear skies and cooler temps.  Winds will blow out of the NW at 20-30mph and temperatures will climb back up into the teens to low twenties F.

The ridge over us today will be forced out by a complex low pressure system which will move into Southcentral Alaska tomorrow evening.  We can expect snowfall to be light and temperatures to rise between Tues and Thursday of this 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: Oct 05, 2019 )

Glacier District
Johnson Pass: ClosedClosed
Placer River: ClosedClosed
Skookum Drainage: ClosedClosed
Turnagain Pass: ClosedClosed
Twentymile: ClosedClosed
Seward District
Carter Lake: ClosedClosed
Lost Lake Trail: ClosedClosed
Primrose Trail: ClosedClosed
Resurrection Pass Trail: ClosedClosed. Will be open for the 2019/20 season pending adequate snow cover.
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.

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