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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Sunday, December 27th 2015
Created: Dec 27th 6:28 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.
2 Moderate Below Treeline / Below 1,000' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
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The Bottom Line

CONSIDERABLE avalanche danger exists in the Alpine where a human could easily trigger a slab 2-3’ thick in steep terrain. Below 2500’ MODERATE avalanche danger exists where triggering 20” of low density snow in a terrain trap could have high consequences. Remember this new snow is sitting on a very weak pre-existing surface and not enough time has passed for the snowpack to adjust to its new load. Large numbers of people will be difficult to manage and warrants extra patience today. Change plans if crowds get too large and multiple people in avalanche terrain becomes a safety concern.

*Another large storm is moving into the area late this evening. If Easterly winds exceed the forecasted amount of 20-40mph today, expect avalanche danger to increase rapidly and adapt to changing conditions.


Primary Concern

Large holiday crowds combined with a recent rapid loading event of 20” of new snow will make safe travel in the backcountry challenging. Today another 3-5” of snow and 20-40 mph ridgetop winds will be adding additional stress to the snowpack. Should crowds start pushing into steeper and more dangerous terrain human triggered avalanches in the alpine are likely. 

Wind Slabs: Today's Easterly winds will be forming new wind slabs on already wind loaded features. These slabs are sitting on a widespread weak layer and could easily produce slabs up to 3’ thick. Be on the look out for blowing snow, shooting cracks, and hollow sounding snow. Avoid steep wind loaded features where the snow is denser on the weaker snow below.

Storm Slabs: In places protected from the wind new snow could be tender and break easily on steep features. As this new snow settles and the slab become more cohesive the weak snow below is something to investigate. Hand pits will allow you to see how well the new snow is bonding to the weak snow below. Experiment on small, steep terrain features with low consequences, and avoid terrain traps.

Loose Snow Avalanches: This problem is a concern in areas with terrain traps, like at the bottom of a narrow gully or abrupt landing, where triggering loose snow could easily bury a person.

Today’s avalanche concerns combined with large holiday crowds are something to be very aware of.  Remember not everyone reads this forecast and understands how to travel in avalanche terrain when hazards are elevated. Here are a few tips to keep in mind:

  • Anticipate others above and below you
  • Wait your turn to avoid putting multiple people on/under large slopes
  • Coordinate with other groups about how to best navigate the terrain
  • Change your plans if crowds get clustered 

Large groups of people on Tincan yesterday made it difficult to know if other groups were above or below you.

 

 20" of low density snow sitting on a weak layer of snow below. Today winds and new snow will be adding stress to this weak layer. Be aware of changing conditions. 


Secondary Concern

Recent strong winds combined with 20” of new snow have been adding stress to this unpredictable trigger.  Avoid being under cornices and anticipate that these loaded guns will break back into a ridgeline further than expected.  Give cornice features a lot of space; should one break it could easily trigger a large slab and send you into dangerous terrain.


Mountain Weather

Yesterday scattered showers brought another 5 inches of new snow to Turnagain Pass. Winds were light 10-20mph from the East. Rain/snow line was around 500’.

This morning ridgetop Easterly winds are already averaging 28mph at Sunburst weather station. Todays winds are expected to be in the 20-40 mph range with another 3-5” of new snow. Rain/snow line could be as high as 800’, but temperatures are expected to increase through out the day.

Another large storm is moving into the area this evening bringing strong Easterly winds and more snow. Another 12” is expected overnight and rain/snow line may rise to 1500’. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 29F  0.4  64 
Summit Lake (1400') 28F   0 17 
Alyeska Mid (1700') 30F  0.46  46 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 22F  ENE   18 45 
Seattle Ridge(2400') 25F  n/a  n/a    n/a 

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: May 16, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedThanks all for a safe and fun season on the Chugach NF! Stay tuned for the 2017/18 season. #playsafe #snowtosealevel
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail will be open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
Summit Lake: Closed

Subscribe to the Turnagain Area Avalanche Advisory:

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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