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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Monday, March 28th 2016
Created: Mar 28th 5:59 am
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
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'
 Show the Complete North American Avalanche Danger Scale
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The Bottom Line

Rain, snow and wind over the forecast region will push the avalanche hazard to CONSIDERABLE today. Wet avalanches and glide avalanches may release naturally at the mid-elevations (between 1,000' and 2,500'). These can be large and destructive slides releasing at, or near, the ground. In the Alpine, wind slab avalanches 6-18" thick, that are composed of the new snow, will be forming and may release naturally. Last, cornices may begin to fall with the warm conditions. 

Travel Advice:
With poor visibility expected today and the chance for large destructive slides, knowing the terrain you are traveling in is key. Simply avoid being under large slopes, runout zones and gullies.


Primary Concern

A fire hose of moisture is pointing our way bringing warm, wet and windy weather to most of Southcentral Alaska. In the Girdwood Valley, Turnagain Pass and Northern Kenai we are seeing light rain up to 1,500' currently with wet snow above this. The rain/snow line is expected to rise as high as 4,000' by tonight... If this happens it will be our highest rain line for the season. Precipitation amounts starting yesterday and ending at 6am this morning vary:

Girdwood Valley: 1.3" water with around 10" wet snow above 1,500'
Turnagain Pass:  Precip sensors are not reading accurately but the snow depth sensor reports 6" of wet snow 
Summit Lake:  ~.3-.5" water with around 4" of snow


WET AVALANCHES: (two types)
1st type, small(ish):  As the storm warms up, rain will begin to fall on the 5-10+ inches of new snow that sits on a crust. Wet loose avalanches will be likely but smaller because they will only be composed of the new snow. Debris could run quite far however.

2nd type, much larger:  If the rain and warm temperatures soften/melt the surface crusts, water will be added to an already moist/wet snowpack at the mid-elevations. In this case we could see large wet loose and possibly wet slab avalanches. These can release deeper in the pack or near the ground creating a much larger and destructive slide.

Image below shows the warm Southerly flow that is pumping into Southcentral, AK.

 

*One of the big questions is, are we now in a "shed cycle"? This is when the snowpack becomes wet and unsupportable and literally sheds off the mountains. The answer is, maybe. It looks like this storm has potential to wet and warm the pack enough below 2,500' (maybe even up to 3,000') that we will start seeing large wet loose and wet slab avalanches. These could be hard to discern with the plethora of glide avalanches out there however. Although at the end of the day, it is a bit of a mess at the mid-elevations at Turnagain Pass...


Secondary Concern

We could see another spike in glide avalanche activity with this warming event. Glide cracks will likely be hard to see with hampered visibility and another reason to stick to mellow terrain with nothing steep above you.

Check out this short clip of a glide avalanche caught on video in the Seattle Creek drainage on Saturday (Credit Allen Garrett). More on that avalanche report HERE. A big thanks to Allen for sending us his photos and video!

We did not see any new glide activity at the Pass yesterday but there were several noted South of Turnagain Pass as well as in Girdwood Valley. 


Additional Concern

At elevations lucky enough to see dry(ish) snow throughout the day wind slab avalanches will be likely. How thick these will be will depend on how much snow has fallen, roughly anywhere from 6-18". The storm will likely keep folks out of these high elevations anyhow, but a wind slab releasing from above may trigger a wet avalanche below.


Mountain Weather

Yesterday's weather consisted of sunny skies in the morning that were replaced by thick clouds and precipitation by the afternoon as the leading edge of a storm system moved in. Light rain has been falling to 1,000-1,500' with wet snow above this. Ridgetop winds were strong overnight with averages in the 20-30's and gusts to 50mph from the East. 

Today, we are expecting this warm southerly flow to continue pushing moisture our way from the Pacific. Temperatures will get warmer by the hour through tomorrow and the rain/snow line could reach the ridgetops by tomorrow night (that's up to 4,000'). Temperature at 1,000' should rise to the 40's today. Between .5 and 1" of water equivalent is expected with another ~.25-.5" tonight. Ridgetop winds should remain strong, in the 20-30mph range with stronger gusts from the East.

Tomorrow, Tuesday, the moisture should push off to the East before another Southerly flow points our way possibly on Wednesday or Thursday.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 32  ??  128 
Summit Lake (1400') 33  0.3  44 
Alyeska Mid (1700') 32  10  1.3  110 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 23  NE  20  51 
Seattle Ridge(2400') 25  SE  24  51 

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 25, 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: Open
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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