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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   John Fitzgerald  
Monday, March 23rd 2015
Created: Mar 23rd 6:24 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.
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.
0 NO RATING Below Treeline / Below 1,000'
 Show the Complete North American Avalanche Danger Scale
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The Bottom Line

The danger is MODERATE in the Alpine today, where the possibility exists for pockets of slab 2-3’ thick to be triggered on steep slopes.  While the likelihood of triggering is trending towards the low end of the scale, the consequences are high enough to injure or bury a person.  Wet loose avalanches will be higher on the likelihood scale and lower on the consequence scale, as volume will be generally low but increase on steep sustained slopes.  Cornices will feel the heat of the sun today and could release naturally.

The danger is LOW this morning at Treeline.  Daytime heating will increase the chances for shallow wet loose avalanches and nudge the danger to MODERATE in steep terrain over 40 degrees.


Primary Concern

It has now been 5 days since the last loading event occurred.  In that time we have seen a daily cycle of melting and freezing on sunlit aspects and generally mild temps.  This pattern has helped 2-3’ slabs that formed last week to become less reactive.  In some areas these slabs are resting on a thin layer of weak faceted snow.  In areas where we have been able to find this combo, there still exists the possibility of triggering one of these slabs.  This problem is variable across the landscape, as it is not something you will find on every slope.  Digging in the snow can help you to understand the problem better, but could also be misleading.  

How do we manage this uncertainty?  By using effective terrain management techniques.  Only expose one person at a time on suspect slopes, use islands of safety for spotting and re grouping, and identity escape routes.

Recent slab avalanche at 3,500' W aspect.  Debris pile visible left of center coming out of the shadow. 

Slab at head of Ingram Cr


Secondary Concern

The more likely avalanche concern today will be wet loose avalanches.  These will be generally low in volume and are easy to anticipate.  Volume will increase on steep sustained slopes.  As the days get longer, so does the amount of terrain that the sun affects increase.  Steep slopes being impacted by direct sunshine will continue to shed shallow loose snow avalanches.  Several natural wet loose avalanches that triggered shallow wet slabs were observed in the Girdwood Valley yesterday.  More of the same is possible today.

Pay attention to the snow surface on sunlit aspects today.  As your skis or board begin sinking more than several inches it will be important to begin dialing back slope angles.


Additional Concern

Cornices grew significantly with last week’s storms.  Direct sun and a lack of wind will help to weaken these features.  As always give cornices a wide berth.  Minimize time spent underneath and make sure you can see the profile before approaching any corniced ridges.


Mountain Weather

Yesterday brought abundant sunshine under clear skies.  Temps were mild and winds were generally calm.  No new precipitation was recorded.

Today looks to be a carbon copy of yesterday, with slightly warmer temps.  Temperatures will reach into the low 40s F at 1,000’ and near 32 F along ridgetops.  Winds will be calm and skies will be clear.

High pressure stretching from Southeast Alaska through Southcentral and into the interior will prevent a low pressure system centered over Bristol Bay from impacting the area.  This pattern looks to break down by mid week as we return to warm and wet Southerly flow.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 33 0 0 55
Summit Lake (1400') 30 0 0 12
Alyeska Mid (1700') 35 0 0 32

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 27 var 4 14
Seattle Ridge(2400') 29 var 4 15

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: May 16, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedThanks all for a safe and fun season on the Chugach NF! Stay tuned for the 2017/18 season. #playsafe #snowtosealevel
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail will be open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
Summit Lake: Closed

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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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