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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   John Fitzgerald  
Monday, February 9th 2015
Created: Feb 9th 6:48 am
2 Moderate Alpine / Above 2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
1 Low Treeline / 1,000'-2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
0 NO RATING Below Treeline / Below 1,000'
 Show the Complete North American Avalanche Danger Scale
The Bottom Line

The avalanche danger is generally LOW on Turnagain Pass.  Isolated pockets of slab up to 8” in depth may be encountered on steep leeward slopes in the Alpine.  It is in these areas where the danger is MODERATE today.

In the Girdwood Valley the danger is MODERATE in the Alpine, where recently formed wind slabs 6-8" (and up to 1') in depth rest on a layer of weak snow.  Avoidance of steep terrain harboring stiff wind loaded snow will be important today.


Primary Concern

The last 3 weeks of clear and cool weather has helped to create very weak snow on the surface throughout the forecast area.  A lack of significant loading from precipitation or wind has kept avalanche activity to a minimum.  An exception to this was found over the weekend in the Girdwood Valley, where strong Northerly winds on Friday loaded fresh slabs onto this weak snow surface.  Turnagain Pass was shielded by the Chugach Range from this outflow wind event.

What this leaves us with is a tale of two different snowpacks.  

On Turnagain Pass, the core of the forecast area, you will find very shallow pockets of fresh slab 3-4” deep that have built as a result of light snowfall and moderate winds over the past 24 hours.    Wind will help to build slabs as thick as 8” by the end of the day on leeward slopes.  These pockets could become deeper if additional snowfall exceeds the forecasted 2-3” snow for today.

In the Girdwood Valley you can expect to encounter stiff wind slabs in the mid to upper elevations that are several days old.  These slabs are hard and sitting on very weak snow.  These slabs will grow slightly today with average depth in the 6-8" range.  It is important to be able to recognize wind loaded features.  Wind loaded slopes will feel stiff and sound hollow.  Shooting cracks radiating from your skis, board or feet are an obvious indicator of unstable snow.


Secondary Concern

In areas not affected by wind, expect sluffing to occur easily in steep terrain.  New low density snow combined with the older weak snow will be easy to trigger and low in volume.  If visibility allows travel into upper elevation steep terrain today, watch any sluff that you trigger and steer away from it.


Mountain Weather

A frontal boundary pushing up from the south has helped to bring about a change over the past 24 hours.  Light amounts of snow have accumulated, with 2” of new snow on Turnagain Pass.  Temperatures have seen a pronounced upswing, with ridgetop stations reading in the teens to 20 F range this morning.  Winds out of the East have also picked up with Sunburst reporting averages in the teens to 20 mph overnight.

Today expect showery conditions.  Snowfall amounts will be light, in the 2” to 3” range.  Ridgetop winds will be out of the East at 10 to 15 mph.  Temperatures at 1,000’ will be in the mid to high 20s F.

An unsettled pattern will help to bring chances for snow through the coming week.  Temperatures will fluctuate and gradually rise as we move through the work week.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 11 2 .1 33
Summit Lake (1400') 7 trace trace 7
Alyeska Mid (1700') 10 2.3 .12 24.5

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 13 E 12 35
Seattle Ridge(2400') 12 var 6 18

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: Mar 28, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: OpenPlease park on road in and leave the turnaround (near outhouse) open for trailers to turn around.
Placer River: OpenPlacer remains open but SKOOKUM DRAINAGE will close to motorized use on April 1st.
Skookum Drainage: OpenSKOOKUM DRAINAGE CLOSES TO MOTORIZED USE ON APRIL 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: Open
Seward District
Carter Lake: Open
Lost Lake Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Primrose Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
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: Open
South Fork Snow River Corridor: Open
Summit Lake: Open

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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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