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Avalanche Advisory

Turnagain Area Avalanche Advisory
Monday, January 29th 2018 5:42 am by Wendy Wagner
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche danger is MODERATE above 1,000' for triggering a slab avalanche 1-2' thick in the Turnagain Pass zone. In the Girdwood Valley, slabs could be up to 3' thick and due to stronger overnight winds, the danger could be trending to CONSIDERABLE. Slopes with recent wind loading will be the most suspect for triggering an avalanche. Additionally, watch for easily initiated loose snow avalanches (sluffs) on steep slopes and at high elevations, above 3,000', there is still a chance someone could trigger a deep persistent slab avalanche. The danger is LOW below 1,000'.


 Show the Complete North American Avalanche Danger Scale
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.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Avalanche Problem 1

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

After an exciting day of several human triggered avalanches Saturday (with no one caught), yesterday we had no reports of avalanche activity, nor did we see any. If you know of an avalanche yesterday, please let us know HERE. Avalanches on Saturday were a function of 1-2' of new snow from Jan 26 that fell on buried surface hoar. The snow was so light that it was only in scattered areas where it was cohesive enough to act like slab, and hence folks were able to trigger slab avalanches. The cold and clear weather is taking the light snow and continuing to loosen it though the faceting process. This is slowly eating away at remaining slabs out there. Despite this, there is still the possibility of finding and triggering one of these lingering slabs. 

With cold and clear weather on tap this week, the big question for increasing avalanche danger will be what are the winds doing? There is plenty of loose snow available for transport and wind slabs could form quickly. So far the Turnagain Pass area has escaped any moderate/strong winds, but it does not seem that way in the Girdwood Valley. Ridgetop winds here increased overnight for a period into the 20'smph with gusts to 40mph, enough to transport snow. If you are headed to the Girdwood Valley area, be on guard for recent wind loading and potential for more dangerous avalanche conditons. Fresh wind slabs are likely to release on, or step down to, buried surface hoar under the Jan 26 snow and could be very touchy and run further than expected. 

Quick hand pits to check how the top 1-2' of snow is bonding is a good way to assess the conditions along your route. Additionally, watching for any shooting cracks, whumpfing, recent avalanche activity and any wind affect/loading patterns will be key for avoiding unstable slopes. 

Surface conditions at mid elevations at Turnagain Pass - loose faceting snow with a new crop of surface hoar on top. (photo: Ray Koleser)


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Avalanche Problem 2

Dry Loose

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Watch your sluff - loose snow avalanches ‘sluffing’ is possible on steep terrain features protected from wind. As the cold weather continues to loosen and facet the top foot of the snow, we are expecting sluffs to become larger and faster by the day.


Additional Concern

Deep Persistent Slabs

Triggering a deep slab is becoming unlikely, but is still not out of the question above 3000'. At these high elevation zones there are a variety of weak layers in the mid pack and near the ground. The most likely trigger spots are in thin areas in the snow cover, often near rocks, or where the slope rolls over. The Southern end of Turnagain Pass to Johnson Pass is more suspect for triggering a deep slab due to a thinner snowpack. 


Mountain Weather

Yesterday's weather saw valley fog up to 2,000' with brilliant sunny skies above. Ridgetop winds were Northerly in the 5mph range and bumped up to 10mph overnight briefly with gusts to 20mph - the exception is Girdwood Valley where ridgetop winds from the NE overnight were in the 20'smph with gusts to 40mph. The inversion remains in place as temperatures stayed in the single digits in valley bottoms and in the teens F at mid and upper elevations.

Cold and clear weather (with valley fog) is again expected for today. The coldest station reporting this morning is the Granite Snotel near Johnson Pass trailhead at -13F, burr. The inversion will keep temperatures in the -10 - +5F range in valley bottoms and in the teens at the mid and upper elevations. Ridgetop winds are expected to be Northerly between 5-15mph.

Looking into the crystal ball, weather models have the cold air mass over Alaska in place for the remainder of this week and through the weekend - this means cold/clear weather with an eye for what the outflow winds are doing.

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 15  68 
Summit Lake (1400') 19 
Alyeska Mid (1700') 10  54 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 16  NE  21 
Seattle Ridge(2400') 16  17 

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 06, 2018 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed as of April 20th
Placer River: ClosedClosed as of April 17th
Skookum Drainage: ClosedClosed as of April 1st.
Turnagain Pass: ClosedClosed as of May 7th. Happy summer, see ya when the snow flies!
Twentymile: ClosedClosed as of April 13th
Seward District
Carter Lake: ClosedClosed as of 4/27
Lost Lake Trail: ClosedClosed as of April 13th
Primrose Trail: ClosedClosed as of April 13th
Resurrection Pass Trail: ClosedClosed as of April 20th
Snug Harbor: ClosedClosed as of 4/27
South Fork Snow River Corridor: ClosedClosed as of April 13th
Summit Lake: ClosedClosed as of April 20th

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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