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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Aleph Johnston-Bloom  
Friday, January 29th 2016
Created: Jan 29th 4:14 am
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
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.
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

A CONSIDERABLE avalanche danger exists in the Alpine where a person could trigger an avalanche on slopes 30 degrees and steeper in Turnagain Pass and Girdwood. The snowpack still needs time to adjust to the 3" of precipitation (apprioximately 2-3' of snow) that has fallen since Tuesday night. Careful route finding and conservative decision-making will be crucial. Wind loaded areas, cornices and glide cracks should be avoided.

A MODERATE avalanche danger is present below 2500’ where the snowpack is wet and saturated and triggering a wet loose avalanche or wet slab on a steep slope is possible.

Below treeline a LOW danger exists where triggering an avalanche is unlikely.

Elevated caution and careful snowpack assessment is recommended for Summit Lake where strong winds and new snow have added stress to a thin snowpack. Click HERE to read the most current Summit Lake Summary and HERE for an observation from Wednesday. 


Primary Concern

Approximately 3' of snow or 3" of rain has fallen in the advisory area since the storm started Tuesday night. This combined with strong ENE winds Tuesday through Thursday has created dangerous conditions in the mountains. Visibility was limited yesterday but fresh debris from a large natural avalanche was observed off of Seattle Ridge. The snowpack will still need time to adjust to this load today and allow the new snow to bond to the old snow surfaces. Elevated caution is advised. Slab depth, especially in wind loaded areas could be deep and very dangerous. Avoid slopes steeper than 30 degrees and be aware of what terrain is above you. Triggering a wind slab in leeward areas is likely. Look for patterns of wind loading, steer clear of stiff pillowed snow and watch for shooting cracks. 

The warm wet snow combined with wind is prime cornice building conditions. Avoid travel underneath or on top of these today. They may easily fail naturally or under the weight of person or machine. When they fall they could overload slopes below and trigger a large avalanche. 


Secondary Concern

A majority of the precipitation that fell on the snowpack in the Treeline elevation band (1000'-2500') has been in the form of rain or very wet snow. This has created saturated conditions and the potential for wet loose and wet slab avalanches. This may change throughout the day as the temperatures are forecasted to drop. This could help stability increase as the snowpack freezes. On the flip side watch out for areas that receive direct sunshine (south facing) if skies clear, this may increase wet loose activity. We are at that point in the AK winter season where this will start becoming an issue. Avoid travel on steep slopes in this elevation band, especially areas where you could end up in a terrain trap.

 

Wet debris from Seattle Ridge. This avalanche ran almost into the flats near the motorized lot on Turnagain Pass yesterday. 

  


Additional Concern

Limited visibility yesterday made it hard to see how the glide cracks were behaving. The snowpack received extra weight and lubrication from rain and warm temperatures. This may cause increased glide activity and so may the cooling temperatures throughout the day. Glides are totally unpredictable. Avoid travel underneath them. We sound like a broken record as they have been in the forecast now for weeks however; they are really not something to mess with. 

 


Mountain Weather

Yesterday skies were mostly cloudy with some clearing in the afternoon. Rain and snow continued to fall adding an additional .5" of precipitation (5+" of snow above 1500') to the snowpack. This brings our storm total to right around 3'' of H2O (2-3' of snow). ENE winds decreased throughout the day becoming calm overnight and temperatures were in the mid 20Fs @ 3000' and in the mid 30Fs @ 1000'.

Today there will be scattered rain and snow showers mostly before noon with a clearing and cooling trend throughout the day. Winds will be calm and temperatures will be in the mid 20Fs to mid 30Fs.  Tonight temperatures are forecasted to drop down into the teens and there is a chance for isolated snow showers. 

Saturday will be mostly sunny as a stabilizing ridge dominates the weather pattern for the day. Clouds move back into the area overnight. Stay tuned for the next round of stormy conditions next week. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880')  30 .3  97 
Summit Lake (1400')  34 .1 28 
Alyeska Mid (1700')  33  4.5 .7 72 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)

Sunburst (3812')

26  E* 10* 41* 
Seattle Ridge(2400')  27  n/a n/a   n/a

*Sunburst anemometer has been down since 7 pm, 1/28.

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: Apr 28, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: ClosedSKOOKUM DRAINAGE CLOSED TO MOTORIZED USE ON APRIL 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: OpenOpen thru May 14th.
Twentymile: Closed
Seward District
Carter Lake: OpenClosed May 1.
Lost Lake Trail: OpenClosed May 1.
Primrose Trail: OpenClosed May 1.
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: OpenClosed May 1.
South Fork Snow River Corridor: OpenClosed May 1.
Summit Lake: OpenClosed May 1.

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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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