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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Tuesday, March 12th 2013
Created: Mar 12th 6:53 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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The Bottom Line

The majority of terrain in the mountains of the Eastern Turnagain Arm has a LOW avalanche danger. However, pockets of MODERATE danger do exist for cornice falls and loose snow avalanches. Cornices are large, potentially unstable and should be avoided from both above and below.  Human triggered dry loose snow avalanches on steep shady slopes should be expected. Additionally, in areas the winds are calm enough to allow the surface crusts on south aspects to warm with today's sunshine, damp/wet snow sluffs are possible.


Primary Concern

Cornice falls will be our primary concern. These behemoths have the potential to break on their own as well as with the added weight of a person/people. They are by far the most dangerous avalanche issue right now as they could fall in bus sized (or bigger) masses and tumble to valley bottoms. Add to that the large amounts of snow that can be entrained, or avalanches triggered, along the way and a quiet day in backcountry can quickly change. We have had a handful of these calve off during the past 2 weeks, with the most recent sometime around Saturday March, 9th - as seen in the photo below.

Predicting cornice failure is very challenging, but intense sun with calm wind increases the likelihood. Giving these guys a wide berth is necessary while traveling on ridgelines as well as underneath them. This includes being mindful of any place you stop - for example, to eat lunch, watch your buddies hill climb or put on your skins.


Secondary Concern

Loose snow avalanches (a.k.a. sluffs) should be fairly easy to initiate today on slopes 40 degrees and steeper. This was the most common issue yesterday. These will come in the form of:

Dry snow - Fast moving but fairly low volume sluffs can be expected on steep shady aspects. With our cold temperatures, shady slopes are becoming looser by the day as the surface snow is faceting.

Wet/damp snow – Southerly aspects will have a crust this morning that might bake down with today’s sunshine and become soft by the afternoon. Light to moderate winds are on tap however and may limit warming of the surface. If crusts do soften expect slow moving damp/wet sluffs to occur. The steeper and more sustained the slope the higher volume and more concerning the sluff. These easily avoidable avalanches can quickly get out of hand in the right terrain where they can pile heavy snow up in gullies quickly for example.

Additional Concerns:
Wind slabs:  North and easterly winds approaching 20mph are possible in scattered areas today. It will be good to keep an eye out for both any fresh slabs formed by this slight bump in wind or old stubborn wind slabs from last week’s high wind event. Any wind slab issue is likely to be confined to the steep “extreme” terrain.

 

Surface conditions:
Surface conditions are exceedingly aspect dependent (it is March after all).  The northern half of the compass sports mostly soft settled powder with varying degrees of stiffer wind effected snow just below the surface.  The southern half consists mainly of sun crusts. Surface hoar now covers all of these aspects above treeline and is a potential future problem when buried by the next snowfall.


Mountain Weather

Sunny skies prevailed in most areas yesterday with a few low lying clouds. Temperatures rose to the mid 20’sF on the ridgetops and mid 30’s at sea level. Winds were light from the northwest ~5mph.

Today, intense sun with a cool breeze is in the forecast. Skies are clear this morning and temperatures overnight have dropped to the teens across the board – low teens at sea level and mid teens on the ridgelines. Winds early this morning have shifted NE and bumped up slightly to the 10mph range with gusts to 20mph. Through the course of the day, temperature should rise to the low to mid 20’sF on the ridges and 30’s at sea level. Ridgetop winds are forecast to remain around 10-15mph from a northeasterly direction.

The high pressure centered over the Bering looks to remain through tomorrow with the associated clear skies over our area. Thursday a low pressure moves in from the Gulf bringing a chance for flurries and partly cloudy skies.

 


 

Kevin will issue the next advisory tomorrow morning, March 13th.

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: Dec 08, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedRain and snow have fallen in Turnagain Pass this week, but not enough to open for snowmachining. Continue to check back to this site for updates.
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail is expected to open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
Summit Lake: Closed

Subscribe to the Turnagain Area Avalanche Advisory:

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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