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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Tuesday, February 10th 2015
Created: Feb 10th 6:11 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.
1 Low Treeline / 1,000'-2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
0 NO RATING Below Treeline / Below 1,000'
 Show the Complete North American Avalanche Danger Scale
The Bottom Line

MODERATE avalanche danger exists at the Alpine elevations (above 2,500') for fresh wind slab avalanches. Wind slabs up to 10" in depth may be found on leeward slopes in areas with 4-5" or more of new snow. Additionally, sluffs will be easy to trigger on steep slopes at all elevations and could run faster than expected.

A LOW avalanche danger can be found in terrain that is sheltered from the wind and where only a few inches of snow has accumulated. 


Primary Concern

After a long three week dry spell, we finally got a fresh coat of paint yesterday with a bit more on the way today and tomorrow. Normally, we wouldn't bat an eye at a couple inches of fluffy stuff here and an inch there - but not this season! Snowfall totals from around the region yesterday were: (keep in mind this is VERY low density snow)

  • 10" in Portage Valley (see photo below)
  • 5" at Turnagain Pass North side (Eddies)
  • 3-4" at Turnagain Pass (Sunburst)
  • 1-2" at Turnagain Pass Southern side (Johnson Pass trailhead)
  • 3" in Girdwood Valley
  • 1" at Summit Lake

WIND SLABS
Unfortunately, the winds picked up last night from the East and will continue to blow today in the moderate range (15-25mph). This is prime wind loading speed and slab development for areas with new snow. Slabs will be forming on very weak faceted (sugary) snow and expect them to be touchy and easy to trigger. However, they should be quite shallow and soft, only packing a real punch in areas with 4-5" of new snow where slabs could be up to 10" thick - these areas of course are where many of us will seek out. The best clues to watch for will be: winds actively loading slopes, stiff feeling snow and cracks shooting from your skis/board. 
 

SOFT SLABS from Warming Temperatures:
Along with the winds forming slabs, warming temperatures will also encourage the new snow to become more cohesive and 'slabby'. In areas with over a few inches of new snow (such as Eddies Ridge), watch for shallow soft slabs, as the new snow overlies very weak snow.


Secondary Concern

With varying amounts of new snow sitting on pre-existing loose faceted snow, you can bet sluffs will be easy to trigger on slopes over 40 degrees. These will be higher volume than we have seen and fast enough to catch you if you're not careful. At the mid-elevations where a crust sits under the loose snow, expect sluffs to be faster than in the higher elevations.

Portage Valley ice climbers:
Wind and warming temperatures could cause natural small avalanches in yesterday's snow to flush through gullies and over climbing routes. Heads up!

Yes, it is true, 10" of snow in the Portage Valley (photo: Graham Predeger)


Mountain Weather

During the past 24-hours we have seen mostly overcast skies with a few flakes adding a trace of snow. Ridgetop winds have been slowly increasing from a generally Easterly direction overnight, averaging ~20mph with gusts into the 30's. Seattle Ridge is blowing from the South, which is uncommon for this main flow direction. Temperatures have been climbing as well and the longtime inversion is scouring out quickly - valley bottoms are ~30F while ridgetops are ~20F this morning.

Today we can expect overcast skies and light snow showers to add up to an inch or two. Winds will be the main player as they are forecast to continue in the 15-25mph range from the East. Temperatures should remain near 20F on the ridgetops and the low 30'sF at sea level and valley bottoms.

Looking forward to Wednesday and Thursday, continued light snowfall is on tap. An embedded short wave associated with a large low pressure system South of the Alaska Peninsula should give us a couple inches each day. Warm air is also on tap... By Thursday we could see rain showers to sea level with a rain/snow line as high as 1,000'. Stay tuned.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 26  tr  33 
Summit Lake (1400') 23  0.1  8
Alyeska Mid (1700') 26  0.9   23

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 18  12  33 
Seattle Ridge(2400') 21  SW  15  34 

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 28, 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: OpenPlacer remains open but SKOOKUM DRAINAGE will close to motorized use on April 1st.
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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