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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   John Fitzgerald  
Friday, March 22nd 2013
Created: Mar 22nd 5:54 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.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
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Alyeska Resort
The Bottom Line

The avalanche hazard will increase to MODERATE this afternoon as new snow and wind build slabs above treeline.  These slabs will be sensitive to human triggers, especially in steep terrain. Below treeline the hazard will remain LOW where snowmachine and skier triggered avalanches are unlikely today.


Primary Concern

New Wind Slabs

New snow and wind will work together to form wind slabs in the mountains today.  Do you remember what the snow surface looked like yesterday?  I do.  On south aspects (southern half of the compass) the surface was very firm and crusty.  Some areas on south facing slopes were holding a thin layer of loose snow. On north aspects (northern half of the compass) the surface snow was a wild mix of loose snow, firm crusts and slabs.  The overall surface pattern is what we call a potentially poor interface; faceted snow & crusts will behave as weak layers & bed surfaces respectively for avalanches today.  The question you will need to answer is: how big is this new slab?  The bigger the slab, the bigger your problem will be.  If precip totals trend toward the higher end, expect to see pockets of wind slab in the 12" range today.

Old Wind Slabs
Yesterday my partners and I encountered older wind slabs that were formed by high winds earlier this week (Tuesday night).  Several parties have also reported triggering wind slabs up to 18" in depth in the past two days.  These older slabs will be harder to trigger today but are worth avoiding, especially in steep terrain.


Secondary Concern

The most recent cornice fall observed in the region occurred in the last 2 days.  These backountry bombs have been dropping sporadically on their own over the past several weeks and have been large enough to do significant damage to a group of people.  New snow and wind will help to increase the sensitivity of aging cornices.  Avoidance is the only way to truly "manage" this type of problem.  Approach ridge crests with caution and don't move out onto a ridge until you can see the snow below you.  Limiting your time below cornices will also help in avoiding this problem.


Mountain Weather

In the past 24 hours the mountains around Eastern Turnagain Arm have seen temperatures average 11 degrees F at the Seattle Ridge weather station (2,400').  Winds at this site have averaged 12 mph out of the SE with gusts to 31 mph.  Precipitation has just begun this morning and stations are just beginning to report snow falling.

Today expect snowfall amounts to be in the 4" to 8" range, with greater amounts in the Girdwood, 20 mile and Placer Valleys.  Temperatures at 1,000' will be in the mid twenties F and ridgetop winds will average 25mph out of the SW.

The extended outlook calls for an active weather pattern to bring more snowfall to the area through the weekend.

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Wendy will issue the next advisory tomorrow morning, March 23rd.

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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