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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Aleph Johnston-Bloom  
Wednesday, March 30th 2016
Created: Mar 30th 4:18 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'
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The Bottom Line

The avalanche danger is CONSIDERABLE today due to continued warm temperatures (above freezing), rain, recent snow and an active glide avalanche cyle. Natural wet loose avalanches in steep terrain are possible and human triggered wet loose avalanches are likely. Cornices fall and isolated wind slabs may also be triggered. Cautious route-finding and terrain evaluation are essential today. Avoid being under the runout of glide cracks.

*If you are headed to the Summit Lake area don't forget to check Summit Lake Summary


Primary Concern

We really need a spring avalanche icon for today to speak to the transitional nature of what is going on. The snowpack is not yet completely in a wet regime but it is on its way. This is most pronounced in the Alpine, where there is still cold dry snow that is being affected by warm temperatures. A number of factors are contributing to the potential for wet(ish) avalanches today. Yesterday was one of the warmest days we have had this spring and there was not a freeze overnight in the mid-elevation band. The surface of the snow was wet over 3000'. Additional rain fell onto storm snow last night, temperatures are forecasted to stay warm today and there is the possibility of afternoon sun. Yesterday it was easy to initiate damp-wet loose avalanches on steep slopes around 2000' and large skier triggered roller balls were observed at 3200' as the snow became damp. The snow from Monday's storm all rests on a crust that is acting as a bed surface for avalanche activity. Hand pits yesterday showed colder snow just above the crust that was creating easy shears. Warmer, damp to wet, snow sits on top of this depending on elevation. This may also make isolated wind slabs easier to trigger (more on this below).

Today’s weather forecast is for rain showers that will add moisture to the snowpack and may cause natural wet loose avalanches in the mid elevation band. In addition, if the sun pokes out at all, it could also be a trigger for natural activity. 

Today a skier or snowmachiner triggering a loose avalanche will be likely on slopes steeper than 35 degrees. Wet loose snow avalanches once initiated can entrain more snow rapidly and are very hard to get out of. They can be particularly hazardous if they push you into a terrain trap and bury you deeply. If your skis or snowmachine are sinking into wet snow this is an obvious clue that the snow is unstable.

Push-a-lanche potential at 2000' on Tincan yesterday. These were gaining momentum and could easily push you into a tree well or tip you over.

Wet/storm slab that occured during Monday's storm on Seattle Ridge with glide avalanche debris from yesterday on top.


Secondary Concern

The glide avalanches keep happening. As a snow geek, I was thrilled to watch one in action from the truck yesterday by Bertha Creek Campground but I was alarmed to see the recent large glide avalanches around the up-track on Seattle Ridge. The glide avalanche in this location also happened in conjuntion with a storm slab. The debris pile is quite large and runs over well-traveled terrain. There is plenty of glide crack potential still looming in this area. The glide cracks are moving, growing and new ones are appearing. We have been saying for months but the message is important, avoid travel underneath glide cracks. 

Glide avalanches on Seattle Ridge including one near the up-track. Note the slab avalanche that also ran and where the debris from both piled up.

 

Glide avalanche above Bertha Creek Campgound. We watched this run at 11:30 am yesterday. This ran over debris from a glide avalanche last week. Photo: Ryan Lewthwaite


Additional Concern

Cornices: Monday's snow and wind made already large cornices noticeably larger. We haven’t seen an active day of widespread cornice failure yet this season.  This just means they continue to grow and creep closer to failure. Warming temperatures this week could act as a catalyst for cornices to fall.  Keep a wide berth both on ridges and when moving below corniced terrain.

Wind slabs: A brief period of wind toward the end of the storm Monday likely built isolated wind slabs in steep leeward terrain in the Alpine. These may be touchy, particularly on unsupported slopes and during the heat of the day and/or when the sun is warming them. They are sitting on a stout melt freeze crust. There is very obvious wind loading, including cross-loaded slopes from the storm. 


Mountain Weather

Yesterday was a mixture of overcast skies and sunshine. Winds were mostly light and easterly. Temperatures were the mid 30Fs to upper 40Fs. Overnight there was rain/snow showers. 

Today is forecasted to be mostly cloudy with rain/snow showers and the rain/snow line at 2400'.  Temperatures will be in the mid 30Fs to mid 40Fs. Winds will be easterly 25-35 mph. There may be some clearing this afternoon and an increase in winds as the front passes.

Tomorrow is a break between storms and then another system rolls in on Friday with hopefully a cooling trend over the weekend.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880')  40  rain .1  125 
Summit Lake (1400')  39  0  0 40 
Alyeska Mid (1700')  35  rain  .2  114

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  29  ENE  10 26 
Seattle Ridge(2400')  31 SE  20   43

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 15, 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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