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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Aleph Johnston-Bloom  
Wednesday, December 6th 2017
Created: Dec 6th 4:15 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.
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.
 Show the Complete North American Avalanche Danger Scale
Alyeska Resort
Special Announcement

**Increased avalanche conditions have been seen across Southcentral, Alaska. This includes at Hatcher Pass, see forecast and recent observations at hpavalanche.org

Motorized use on Turnagain Pass is closed due to insufficient snow cover.  Please see riding area status at the bottom of this page for the most up-to-date information.

Big thanks to the 130 people that came out for the Snowmachine Specific – Avalanche Safety and Lessons Learned last night and to thanks to AMDS for hosting!!! #getthetraining

Join us this SATURDAY in Seward:

Know Before You Go - Avalanche Awareness at the Seward Community Library, December 8th, 1 pm - 4 pm | FREE Join CNFAIC for a great intro to avalanche recognition and rescue, including hands-on beacon practice.

 


The Bottom Line

The avalanche danger is CONSIDERABLE near and above treeline (above 1000'). The recent storm has loaded a weak snowpack. Triggering a slab 2-3+ feet thick is likely on slopes steeper than 30 degrees. Remote triggered avalanches are possible. Cautious route-finding and conservative decision-making are essential today.  

Below 1000’ the avalanche danger is MODERATE where there is minimal snow cover, but an avalanche running from above is still possible.

 


Primary Concern

The facets buried now by both the Thanksgiving storm and the past weekend's storm are still reactive and our main layer of concern. Observers reported multiple whumpfs, shooting cracks and a couple of avalanches triggered on both Monday and Tuesday. Quote from an observation on Monday, "I triggered a couple of house sized collapses and then a city block sized collapse at the top of the 10-15 degree willow slopes during the approach. These released above the crust. This was my spookiest trip up Sunburst ever, in hundreds of trips up it." These red flags are all saying that this snowpack is not to be trusted. Those pesky facets are now buried around 3 feet deep. This means that a slab releasing on them could have high consequences. Snowpack tests yesterday also showed that the facets were reactive with propagation potential but may be a stubborn to initiate. An avalanche may not be triggered by the first person onto the slope but once a failure starts in the weak layer it could travel long distances across terrain and cause a large avalanche. This is not a set-up to mess with. The travel advice for Considerable hazard is important to highlight today. 

Remote triggered avalanche on Sunburst 12.4.17 Photo: Chris Flowers

Small avalanche triggered yesterday on Tincan. Note the slab depth. (Thanks to anonymous observer for sharing)

Pit profile at 2250'. The facets are sitting on an old melt freeze crust 20 cm above the ground. 

 


Secondary Concern

Very high winds (over 100 mph) during the storm Saturday have loaded leeward slopes. An additional 4-6" of snow fell yesterday and ENE winds blew 15-25 mph with gusts as high as 60. Winds slabs are likely found along ridgelines as well as lower down slopes due to those high wind speeds on Saturday. Look for drifting or areas that look "fat". Pay attention to cracking and hollow sounding snow. Wind slabs could be soft or hard depending on exposure to winds and if triggered could release a larger persistent slab lower down on the slope. Today is not the time to be pushing into steep terrain. Avoiding slopes greater than 30 degrees is recommended.

 

Wind loading on leeward slopes, CFR. 

 


Mountain Weather

Yesterday skies were overcast in the morning with rain showers at sea level and snow falling above approximately 700', adding 4-6" of snow to the snowpack. The precipitation tapered off and the skies became broken in the afternoon. Winds were easterly 15-25 with higher gusts into the 50-60s. Temperatures were in the mid 30Fs at sea level and the mid 20s at ridgeline stations. There was slight cooling overnight. 

Today is forecasted to be mostly to partly cloudy with a chance of snow showers in the morning. Winds will shift to the north, 5-15 mph. Temperatures will be low to mid 30Fs at 1000' and low to mid 20Fs at 3000'. Temperatures should dip into the low 20Fs overnight but then climb again Thursday morning as the next wave of forecasted moisture moves into the area. Again timing, precipitation amounts and temperatures are not certain. The models are having trouble with these waves beyond 24 hrs out according to the NWS. Stay tuned. Into the weekend looks to be stormy! For a good visual of the atmospheric river that is sending all the weather into the Gulf of Alaska check out Windy.com.

*Center Ridge SNOTEL is reporting erroneous temperature data. See Turnagain Pass DOT weather station for accurate temperature at 1000'.

**Seattle Ridge anemometer is rimed.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 32* .3  32 
Summit Lake (1400') 30   1  .1  12
Alyeska Mid (1700') 33  .4  20

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 24  ENE   20 63 
Seattle Ridge(2400')  27 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: Dec 08, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedRain and snow have fallen in Turnagain Pass this week, but not enough to open for snowmachining. Continue to check back to this site for updates.
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail is expected to 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
© 2017 Chugach National Forest Avalanche Information Center. All rights reserved.
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