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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Thursday, April 7th 2016
Created: Apr 7th 6:13 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.
3 Considerable Treeline / 1,000'-2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
0 NO RATING Below Treeline / Below 1,000'
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Anchorage Snowmobile Club
Special Announcement

FREE rescue clinics and general avalanche information for those headed to Arctic Man this week.  Click HERE for more information.  The snowpack has been reported to be very unstable in the Hoodoos with many human triggered avalanches over the weekend. Please be on your guard and don't forget your beacon, shovel and probe.

 


The Bottom Line

The avalanche danger is CONSIDERABLE below 3000’ due to the potential of large destructive glide avalanches. There are several areas where glide cracks threaten poplar terrain and travel in these zones is discouraged. Cautious route-finding and terrain evaluation are essential to avoid being under the runout of glide cracks.

In the Alpine the avalanche danger is MODERATE above 2500’, where skier triggered wind slabs and wet avalanche are possible. This danger will depend on snow depths and will increase with solar exposure on specific terrain features.

*As glide avalanches continue to release, summer use trails with avalanche terrain above should be avoided. The Byron Glacier trail in Portage Valley is not recommended and the Turnagain Arm Trail between Bird and Girdwood, remains CLOSED.


Primary Concern

Glide avalanches continue to be the primary concern in the mid elevation band below 3000'. Many large glides have released this week leaving Turnagain Pass covered in dirty brown streaks. Yesterday two new glide avalanches were confirmed on Seattle Ridge and one new one on Pete’s South. The good news is glides can be avoided by simply not exposing yourself to the run-out zone of existing cracks. Unfortunately glide cracks do threaten popular terrain on both sides of the road. The Seattle Ridge snowmachine ‘uptrack’ being of most concern since it has a very large crack that extends into this zone. Since this is the only route to the back bowls of Seattle Creek, this proposes a challenging dilemma and should warrent a discussion within your group. The bottom line is, should you choose to go, limit your time in this zone, travel one at a time, and don't high mark under this huge crack. If you were to be in the wrong place at the wrong time getting caught up in a glide avalanche will undoubtedly be unsurvivable.

This picture was taken on April 2, but still reflects similar conditions near the Seatte Ridge uptrack. 

 

 

Although glide avalanche frequency has decreased since this past weekend, there is still a lot of potential for more glide avalanches on Seattle Ridge.

 

New glide release on Pete's South (middle one is new.) Photo by Tim Glassett


Secondary Concern

The possibility of wet loose avalanche activity will increase with warming daytime temperatures. In the mid elevation zone below 2000’ it will be important to monitor the surface crust. Due to recent rain showers and cloud cover this zone hasn’t been getting a good “re-freeze” overnight. Yesterday by 3:30pm the surface crust had completely disappeared and the snow was becoming very punchy causing skis to sink in 8-10”. Should you experience this today, stay off of slopes steeper than 35 degrees and avoid terrain traps.

In the Alpine, an estimated 4-8” new snow has fallen in the last two days, and deeper amounts are more likely on the Northern side of Turnagain Pass. Unfortunately, we do not have reliable precipitation data for Turnagain Pass right now, so it will be important to pay attention to how much new snow is sitting on the stout surface crust below. Triggering a wet/damp “point release” will increase with daytime temps and solar exposure. This avalanche problem will be minor if new snow depths are shallow. 


Additional Concern

Yesterday moderate Easterly winds and variable snow showers were observed in Turnagain Pass with heavier precipitation observed on the Northern end of Turnagain Pass. Winds slabs up to 8-10” thick are possible on leeward terrain features in the alpine and could be tender on steeper slopes. Monitor snow depths, pay attention for shooting cracks and pillowed shape features in steep terrain.

Cornices:  We are still waiting for the Alpine to warm up enough to start seeing a natural cornice fall cycle.  We do know that cornices are close enough to failure that skiers or snowmachiners can influence a failure by travelling on a corniced ridge and the potential for a human-trigger is a very real concern.  Remember these have a tendency to break much further back than one might expect.


Mountain Weather

Yesterday weather conditions were variable throughout the forecast zone. Continuous moderate rainfall was observed on the far Northern side of Turnagain Pass, North of Tincan. On the South side there was a mix of scattered rain/snow showers and intermittent periods of sun. Rain/snow line was near 1800’. Two inches of new snow was observed yesterday on Magnum mid day. Ridgetop winds were from the East average 15-25mph. Daytime temperatures reached 42F at Center Ridge Wx station (1800’) and overnight temperatures dipped into the low 30F’s for several hours.

Rain and snow showers should be anticipated again today, but with less precip, 1-2” of snow in the Alpine. Rain/snow line will be around 1700’. Temperatures at 1000’ will be in the high 30F’s to low 40F’s. Ridgetop winds will be Light to Moderate from the East.

Tomorrow there’s talk of partly sunny skies before another low pressure moves into the area on Saturday, bringing another round of rain and snow showers. 

 ** The precip data at Center Ridge hasn't been alligning with field observations over the last week. Also Turngain Pass DOT weather station is currently not functioning. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 35  rain  **0.1  116 
Summit Lake (1400') 38  rain  0.1   35
Alyeska Mid (1700') 34  rain  .29   102

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 25  ENE  18  43 
Seattle Ridge(2400') 28  SE  17  39 

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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