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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Kevin Wright  
Wednesday, February 20th 2013
Created: Feb 20th 6:52 am
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
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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The Bottom Line

The blizzard overnight dropped enough snow to raise the danger rating in some areas today.  Weather stations are showing 24 hour snow totals ranging from a couple inches in Summit lake, to 10 to 12 inches at Grandview.  Turnagain Pass and Girdwood got at least 8 inches at mid elevations. 

The danger rating has risen to CONSIDERABLE above treeline where storm snow and wind slab is deep enough to be a problem.  Tender wind slab at high elevations may be the most likely problem today, but we have recently seen deeper avalanches fail both at a 3 week old crust interface and full depth to the ground.


Primary Concern

Storm snow combined with wind overnight with gusts to 70 mph will make dangerous avalanche conditions in higher elevation terrain.  Today, as the snowfall continues to build, we can expect wind slabs 1-2 feet deep to be reactive to human triggers.  It may be difficult to travel above treeline due to poor visibility...

Below treeline, a low to moderate danger exists today.  Some areas in the trees that are more prone to wind loading may have shooting cracks and small reactive wind pillows.  Larger runouts are worth avoiding today until the new snow has time to settle.


Secondary Concern

The persistent slab is the enigma that is keeping us on our toes.  Despite the old age of these weak layers, they remain active on an infrequent basis.  Two specific issues are at play right now -

1.  A crust formed in late January is now 2-6 feet deep.  There was a report of a slide, possibly on this layer in Junior's bowl on Seattle ridge earlier this week.  This layer seems to be a problem only at a focused elevation band between 1900 and 3000 feet, which is mid-elevation for most of our local mountains.

2.  The old October/November facets that have been dormant for the past 6-8 weeks finally showed themselves at Carter lake on Monday.  A snowmachine triggered avalanche slid to the ground on a south facing slope, narrowly missing people watching at the bottom and damaging a couple sleds that were parked. This problem is more likely to be found in the central portion of the Kenai peninsula where the snowpack is thinner and the deeper layers are more easily influenced by the weight of a person or snowmachine.


Mountain Weather

The blizzard warning overnight seemed to bring more snow to Grandview than to Girdwood or Turnagain Pass.  Snowfall is likely more than a foot in some areas over the last 24 hours, with an average closer to 8 inches.  It is still snowing as of 7am this morning.  Wind peaked around 5pm last night and gradually diminished.  Gusts are still reaching into the 30s, which is ideal to move snow around and create wind slabs and cornices.  Temperatures rose from the single digits yesterday morning to the mid to high 20s today.

3-6 inches snow is expected today, with continued moderate to high wind.  Precipitation should remain as snow to sea level.


Graham will issue the next advisory on Thursday, February 21st.

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: Apr 28, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: ClosedSKOOKUM DRAINAGE CLOSED TO MOTORIZED USE ON APRIL 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: OpenOpen thru May 14th.
Twentymile: Closed
Seward District
Carter Lake: OpenClosed May 1.
Lost Lake Trail: OpenClosed May 1.
Primrose Trail: OpenClosed May 1.
Resurrection Pass Trail: ClosedClosed for 2016/17 winter season. This is a non-motorized season. This alternates every other year and will open again during the 2017/18 winter.
Snug Harbor: OpenClosed May 1.
South Fork Snow River Corridor: OpenClosed May 1.
Summit Lake: OpenClosed May 1.

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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
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