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Avalanche Advisory

Turnagain Area Avalanche Advisory
Tuesday, December 25th 2018 7:00 am by Aleph Johnston-Bloom
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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BROUGHT TO YOU BY
The Bottom Line

There is a MODERATE avalanche danger for slopes above 1,000'.  Triggering a cornice fall or a wind slab avalanche will be possible in areas exposed to Saturday's winds. Glide cracks are opening and releasing, avoid travel under them. Pay attention to weather and changing conditions. If snow amounts are higher than forecast expect the danger to rise. Watch for signs of instability. 

JOHNSON PASS / LYNX DRAINAGE / SUMMIT LAKE:  South of Turnagain Pass weak layers exists under 2-3' of snow. Human triggered slab avalanches over 2' thick are possible on slopes over 35 degrees. We are currently gathering information from these areas. Please consider submitting an observation if you head there - thank you!

LOST LAKE:  This zone is out of the advisory area, but is also suspect for harboring weak layers 2-3' below the snow surface due to recent reports. Triggering large slab avalanche should be on the radar here as well. Pay attention for signs of instability like collapsing and recent avalanches. 


 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.
Special Announcement

Dashing through the snow

On whatever we like to ride

Always making sure

We are not underneath a glide

Over the mountains we go

In avalanche terrain one at a time

Wearing rescue gear

And checking the forecast too

Having a safe holiday and wishing one to you! - Happy Holidays from the CNFAIC staff


Avalanche Problem 1

Cornice

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Yesterday we received a report of another cornice fall in Warm-up Bowl possibly triggered by someone walking on the ridge. Sunday night we received multiple reports of cornice falls being triggered that day.  Remember to give cornices a wide berth on the ridge as they can break off further back than expected and potentially take you for a nasty ride. They could also trigger a wind slab or larger avalanche below, creating an even bigger problem. It is also important to limit exposure time below them especially with so many people out enjoying the snow this holiday week. There is snow in the forecast today and increasing winds. This will decrease visibility and make it harder to determine where you are in relation to the cornices. 

If snow amounts are higher than forecast watch for storm slabs forming today. There is weak snow on the surface and the new snow may not bond well to the old. 

WIND SLABS:  Winds are forecast to increase today. Any new snow falling may easily get blown into start zones and begin to form tender wind slabs. In addition, Saturday's sustained NE winds that were strong enough to move snow around and form cornices also potentially created wind slabs on steep, unsupported slopes. Yesterday there were reports cornice falls triggering small pockets of wind slab. Continue to be on the lookout for these today. At this point the older wind slabs may be quite stubborn and could allow a person well out onto them before releasing. Watch for shooting cracks, hollow sounding snow and be especially aware of the terrain - if a wind slab or cornice does release where will you go?

Dog triggered cornice fall on December 23rd. Photo: Andy Moderow 12-24-18

 Magnum ridge cornice, 12-24-18. Photo: Andy Moderow.

 


Avalanche Problem 2

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Buried weak layers roughly 2' below the snow surface have been found in areas south of Turnagain Pass in both the Summit Lake zone and as far south as Lost Lake.  We suspect the snowpack may be similar around Johnson Pass, Lynx drainage and Twin Peaks/Silver Tip. These weak layers are composed of facets associated with crusts and have been showing signs they could be reactive enough a person could trigger a large avalanche.  If you are headed to areas south of Turnagain, keep in mind triggering a large slab avalanche is possible. Listen and feel for whumpfing (collapsing of the snowpack) and look for avalanche activity from the storm that may have steeped down into the deeper layers. 

 


Additional Concern

Glide Avalanches

Yesterday two recent glide avalanches were observed in the Lynx Creek drainage along with multiple opening cracks. Observers reported the glide cracks on Sunburst and in Warm-up (-1) Bowl are opening and continue to see new glide cracks throughout the advisory area. It is important to remember glide avalanches can release at any time and are not associated with human triggers. Limit travel underneath. It's a case of not wanting to be in the wrong place at the wrong time.

 

 Recent glide avalanches in Lynx Creek,12-24-18. Photo: Andy Moderow

 Cornice fall and glide gracks on Sunburst, 12-24-18. Photo: Andy Moderow


Mountain Weather

Yesterday: Skies were mostly clear with some valley fog. Temperatures were in the teens and 20Fs with some valley bottoms hitting single digits. Winds were light. Clouds moved in overnight and temperatures are slowly rising. 

Today: Mostly cloudy skies with snow showers throughout the day, 1-7" is forecast. Winds will be easterly 15-30 mph gusting into the 40s. Temperatures will be in the 20Fs to low 30Fs. Snow showers and gusty winds continue overnight. 

Tomorrow: There is a chance of snow throughout the day with mostly cloudy skies, calm winds and temperatures in the 20Fs to low 30Fs. The overall weather pattern is forecast to be active at the end of the week into the weekend. Fingers crossed for a snowy 2019! #snowtosealevel

*Seattle Ridge weather station was heavily rimed and the anemometer (wind sensor) was destroyed.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 24   0 58 
Summit Lake (1400')  12    0 12  
Alyeska Mid (1700') 25  0  0   32 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  20   NE  28
Seattle Ridge(2400') 23  *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: Mar 22, 2019 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Open
Placer River: ClosedClosed as of 3.20.19 due to lack of snow.
Skookum Drainage: ClosedPlacer access closed as of 3.20.19 due to lack of snow.
Turnagain Pass: Open
Twentymile: ClosedClosed as of 3.20.19 due to lack of snow.
Seward District
Carter Lake: Open
Lost Lake Trail: ClosedClosed as of 3/22. Unfortunately HEAVY rain over the past week has washed much of the snow off the lower stretches of this trail.
Primrose Trail: OpenPlease stay on trail to avoid resource damage through forested areas.
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: Open
South Fork Snow River Corridor: ClosedClosed as of 3.20.19 due to lack of snow.
Summit Lake: Open

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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