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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Friday, March 27th 2015
Created: Mar 27th 6:21 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'
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The Bottom Line

Today the avalanche danger is MODERATE both in the Alpine and at Treeline. Triggering a wind slab up to 2’ thick is possible on steep sustained slopes. If the sun comes out today 1-2' of newly fallen snow will be susceptible to rapid warming and could produce natural wet avalanches on Eastern and Southern slopes. It will be important to avoid large steep slopes and pay attention to surface conditions if the sun makes an appearance today.

Below treeline heavy wet snow conditions could make recovery out of a terrain trap difficult. Keep an eye out for steep gullies, open drainages and tree wells at this lower elevation band.


Primary Concern

Yesterday 1-2' of new snow fell in Alpine of Gridwood and Turnagain Pass and the most intense part of this storm occurred between 2am and Noon.  Ridgetop winds averaged in the mid 20's mph from the Northeast with gusts into the high 40's mph for a 24 hour period.

Storm snow totals are from the last 36 hours:

Turnagin Pass ≈ 1” of water (16” at 2800’)

Girdwood = 2.05” of water (21” at 2800’ at Alyeska)

Summit Lake ≈ 0.1 water (trace)

This new snow will likely gain strength quickly as it settles, but triggering a wind slab up to 2’ thick is possible on steep slopes. Surface conditions below this new snow are variable with a sun crust on Southern and Eastern aspects and pockets of weaker snow on Northern and Western slopes. Today it will be important to avoid large steep sustained slopes and give this new snow a chance to adjust to the variable bed surfaces below.  

 Moderate ridgetop winds yesterday were transporting snow in the Alpine. Photo taken at 3200' on the ridgeline above Common Bowl,Tincan 

 

 


Secondary Concern

Yesterday several loose snow ‘point releases’ and a small storm slabs were observed in steep terrain in Turnagain Pass. This new snow will be susceptible to rapid warming due to solar affect and could cause wet point releases and wet slabs if the sun makes an appearance. It will be important to monitor the sun’s affect today – even thin cloud cover could increase solar affect acting as a large reflector. Pay attention for moist surface conditions and avoid large steep slopes that will have more volume if an avalanche is triggered.

Small D1 point releases "sluffs" and a fresh storm slab on "CFR" on Tincan mid day during a brief window of good visibility. 

 

Day-time temperatures yesterday were warm and rain/snow line moved from 800’ in the morning to 1700’ in the afternoon. This caused a period of rapid melting below this elevation. Today wet loose avalanches on steep terrain features will be an additional hazard below treeline. 8-10” of heavy wet snow could be challenging to move through and early season conditions like open drainages and tree wells exist at this lower elevation band. Avoid terrain traps - it could be difficult to dig yourself out if caught up side down. 

Two photos taken yesterday of the same tree at 1600'.1st picture was taken at 11:30am and the second was taken at 4pm after rain/snow line moved to 1700'. Photo by John Fitzgerald.

 

 


Mountain Weather

Total precipitation for Turnagain Pass was near an inch of water, which was a mix of rain and snow depending on elevation. Rain/snow line was at 800’ yesterday morning, but quickly moved to 1700’ by the afternoon. Temperatures at sea level were in the mid 30’s F to low 40’s F, and upper 20’s F at ridgetops. Ridgetop winds averaged in the 20’s mph with gusts into the high 40’s mph from the NE.

Today rain and snow showers are expected and patches of sun are possible. Rain/snow line will likely be near 2000’ today and up to 3” could fall at higher elevations.  Temperatures will remain warm; high 30’s F at sea level and mid 20's F along ridgetops. Ridgetop winds will be from the East, 10-20 mph.

A low pressure system South of the Alaska Peninsula will bring another burst of rain and snow to Southcentral Alaska over the weekend. This will continue to bring us warm moist air, rain near sea level and snow in the interior and in the Alpine. It is uncertain how much precip will fall. Winds will likely be moderate at times, 20-30 mph from the East along ridgetops. 

 *Seattle Ridge Wx Station is not producing accurate wind direction data at this time. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 34  0.4  60 
Summit Lake (1400') 36  0.1  12 
Alyeska Mid (1700') 34  0.89 32 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 26  ENE  23  49 
Seattle Ridge(2400') 28  * 19  41 

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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