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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Friday, April 15th 2016
Created: Apr 15th 6:34 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'
 Show the Complete North American Avalanche Danger Scale
Silverton Mountain Guides
Special Announcement
  • This is the final week of daily avalanche advisories. Between Monday, April 18th and Saturday, April 30th we will be issuing advisories on weekends and intermittently during the week.
  • Click HERE to read the accident report of a fatal avalanche accident that killed a snowmachiner in the Hoodoo Mountains, Eastern Alaska Range, on April 3, 2016. This is one of 6 avalanche fatalities in Alaska this winter season. 

The Bottom Line

Below 2500' the avalanche danger is CONSIDERABLE today due to a continued pattern of warm temperatures and an active glide avalanche cycle. Natural wet loose avalanches in steep terrain are possible and human triggered wet loose avalanches are likely. Careful snowpack evaluation, cautious route-finding and conservative decision-making are essential to avoid being under the runout of glide cracks.

In the Alpine the avalanche danger is MODERATE. Human triggered wind slabs are possible on steep leeward slopes and cornices are also a concern for this elevation band along ridgelines.

***Travel is not recommended in avalanche terrain on the West (motorized side of Turnagain Pass).

 


Primary Concern

Yesterday’s unexpected sunny weather and warm daytime temps appear to have accelerated yesterday’s glide activity. Numerous glides released between Turnagain Pass and Girdwood Valley including 3 that were captured by the DOT webcam on Repeat Offender during the heat of the day (2:30pm to 6:30pm.) The fact that we have been experience multiple nights without freezing temperatures in the 1000’-2000’ is concerning. This current snowpack combined with today’s weather (rain and possible sun) has us prepared for another round of glide activity.

Today we will continue to push our message to avoid all slopes with existing glide cracks, including all runout zones. Due to the dangerous and destructive power of even a small glide avalanche, we are recommending that people do not travel in avalanche terrain on the motorized side of Turnagain Pass (this include the up-track). Glide avalanche hazard also exists on the non-motorized side of Turnagain Pass. If you were to be in the wrong place at the wrong time getting caught up in a glide avalanche would not be survivable.

Glide activity yesterday on Repeat Offender, Seattle Ridge, as observed by the DOT web cam.

 

Close up view of the Seattle Ridge up-track. Notice all of the glide cracks in this area and a natural wet loose avalanche that occured mid day yesterday (4/14)


Secondary Concern

Yesterday numerous natural wet loose avalanches were observed on Southeast aspects due to intense solar heating. This wet loose activity started around 3pm when temperatures spiked and continued into early evening paralleling yesterday’s glide cycle. Yesterday’s sunny weather was a good reminder of how vulnerable the snowpack is right now in this mid elevation band, where a superficial crust quickly lost its strength.

Below 2000’ overnight temps have remained just above freezing and we have already seen 0.3” of rain in Turnagain Pass and Girdwood Valley. Today we should expect rain and sun, both of which will add stress to the snowpack. If the snow is unsupportable and your skis/snowmachine start sinking into punchy wet snow, this is an obvious sign the snow is loosing its strength.  Today it is important to stay off steep slopes below 2500’. 


Additional Concern

In the Alpine it will be important to be aware of terrain features that could harbor newly formed wind slabs. On leeward aspects and on shaded aspects where the snow is drier, triggering a wind slab (6-10" thick) will be possible. Evaluate snow and terrain features carefully and be on the look out for shooting cracks or blowing snow.

Cornices remain large and warm daytime temperatures will be adding additional stress. Give them extra space and remember they have a tendency to break much further back than expected. 


Mountain Weather

Yesterday skies were mostly sunny and daytime temperatures reached the mid 50F’s near sea level. At Center Ridge Weather station (1880’) daytime temperatures reached a high of 50F at 2pm and overnight temperatures hovered just above freezing. Easterly Ridgetop winds were, 10-25mph. Overnight 0.3" of rain was recorded. 

Scattered rain and snow showers are expected throughout the day with mostly cloudy skis, but periods of sun are always possible. Rain/snow line will be around 2500’ with an addition 0.2” of (snow water equivalent) expected today. Ridgetop winds, averaging 10-20mph, will be from the East.  Daytime high temperatures for 1000’ are expected to be around 45F and overnight lows in the mid 30F’s.

Similar temperatures and showery conditions are expected through the weekend.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 38  rain .3  112 
Summit Lake (1400') 40  29 
Alyeska Mid (1700') 38  rain  .3  97 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 28  ENE  15  37 
Seattle Ridge(2400') 31  11  26 

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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