Avalanche Advisory

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

Increased winds and a modest amount of snow in the forecast today will raise the avalanche danger below treeline to MODERATE today.  If the forecasted precipitation arrives expect shallow wind slabs to be reactive at all elevations throughout the day.

The persistent slab and deep slab problems are of secondary concern today as fresh wind slabs form in the upper elevations, resting on a variety of surfaces.

“Slide for life” conditions will continue to be a serious concern in the mountains around Eastern Turnagain Arm, especially in steep terrain below 3,500’.  Slick, hard crusts are making it very difficult to arrest a fall.

 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.
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Avalanche Problem 1

With literally no snow available for transport in lower elevation terrain (it’s all locked up as one thick crust below 3,000’) the depth of any fresh wind slab will be directly linked to the amount of snow we receive throughout the day in the lower elevations. Expect bonding to be particularly poor between the surface and any new snow, as it will be falling on a very slick and stout crust or surface hoar that has formed over the last week.  If fresh wind slabs build they will be possible to trigger in terrain greater than about 30 degrees today.  With winds predominantly from the north and east, south and west aspects will prove most suspect.

Below 1,000’ any new snow today will be falling on either ice or frozen vegetation where we are essentially building our snowpack, literally from the frozen ground up.

Avalanche Problem 2

In terrain above 3,500’, the last storm cycle laid down mostly snow (as opposed to rain).  Terrain above this elevation is harboring old wind slabs up to a foot in depth resting on weak interfaces.  Add to that more wind and a fresh shot of snow today and it will be possible to awaken a persistent slab.  Again, leeward slopes on the south and west tilt of the compass should be treated as suspicious if you make it into upper elevations today.

Additional Concern

Slabs 3-6 feet thick are sitting on weak snow near the ground in the upper elevations.  It is less likely to trigger a deep slab today in comparison to a more shallow wind slab or persistent slab.  However, the possibility remains for triggering a slab that can pull out snow to the ground.  Unlike the persistent or wind slab concern, deep slabs have the potential to move large volumes of snow.  Avoiding likely trigger points, especially areas where slabs are thinner, will lower the likelihood of triggering a deep slab avalanche today. 

The deep slab problem is not a concern below 3000 feet where the previously water saturated layers have now frozen into a very strong and stable crust layer.

Mountain Weather

Increasing mid and high level clouds yesterday were indicative of an imminent change in weather for our region.  Temperatures were in the mid 20’s with light winds from the north.  Some folks may have even seen a snowflake or two falling at sea level yesterday though it did not add up to more than a trace.

Today the National Weather Service has issued a Blizzard Warning until 7PM for Whittier, Girdwood, Seward and Moose Pass.  Winds from the north and east are expected to pick up throughout the day blowing 40-60 mph and usher in 5-12 inches of snow.  Temperatures look to be in the mid-20’s at 1,000’ and low-teens to single digits at ridgetop locations.  Expect blowing snow to reduce visibility and make travel difficult today.

This pulse of moisture looks to be brief with a return to cold and dry conditions by tomorrow and for the weekend.

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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