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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Sunday, March 22nd 2015
Created: Mar 22nd 5:33 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.
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.
0 NO RATING Below Treeline / Below 1,000'
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The Bottom Line

The avalanche danger is MODERATE on all aspects near and above treeline (above 2,000').  Slabs up to 3' thick resting on weak faceted snow may be triggered by the weight of a person in isolated areas. Additionally, daytime warming and spring-like conditions will increase cornice sensitivity and the potential for wet avalanches late in the day on Southerly aspects.


Primary Concern

Variability continues to be the theme of this weekend's snowpack. Slabs 1-3 ft thick that formed over the past week rest on a variety of surfaces.  In some places the slab is bonded well to what is below, while in others it sits on a layer of facets that still have the potential to propagate and avalanche.


Where do the pockets of facets exist? The complexity of the current situation is trying to figure this out. You could dig in one spot and 10 ft over have a completely different structure. Some areas avalanched during the Post St. Patty’s day storm and then were covered up by the next snow on Thursday hiding the evidence and adding to the tricky nature of this snowpack. The facets may have been blown away by winds before the storms higher on the slope yet part way down the run be present and reactive.  Obvious clues may not be seen, however collapsing (whoomphing) does continue to be observed in certain areas and is a sure sign that facets exist in that location (photo below).



These conditions can be the type that allow multiple folks to travel down the slope before one hits the sour spot and triggers an avalanche. If you choose to go into avalanche terrain the potential of a slab/facet setup needs to considered and respected.  

Use good travel practices: travel one at a time, have escape routes planned and avoid trigger points and terrain traps. Be cautious on slopes 35 degrees or steeper.


Secondary Concern

Cornices have grown significantly from the past week’s storms and are hazards in some areas.

Warming throughout the day can make these more likely to release naturally or under the weight of a traveler. Give them a wide berth while traveling below or next to and remember they often break farther back than you expect.  The extra load of a falling cornice can trigger an avalanche if there is unstable snow where it lands.


Additional Concern

It's springtime! By late in the day yesterday (~4-5pm) the snowpack below 2,000' became wet and unsupportable while the upper elevations became damp; these surfaces have refrozen overnight. Warming should be expected again today and as the snow heats up, wet loose "push-a-lanches" will be possible on steep slopes. Although it's more of an outlier, there is a chance for pulling out a wet slab in areas with poor snowpack structure basking in the sun.


Mountain Weather

It was very warm and mild yesterday as thin clouds filled the skies and lowered visibility to mostly "gray bird" conditions. Temperatures reached the low 40's at 1,000' and near 32F on the ridgetops. Winds were light and variable with no precipitation since Thursday. 

Today, another warm day is in store with mostly sunny skies. Temperatures should reach the mid 30'sF on the ridgetops and low 40's in the parking lots once again. Ridgetop winds will continue to be light and variable.

This mild spring-like weather should remain until Tuesday afternoon when a large North Pacific low develops and looks to usher in a warm, wet and windy storm. 

"Greenhouse effect"? Yesterday we saw what avalanche practitioners call a greenhouse effect, or "greenhousing". This is when there is a thin layer of clouds that let much of the solar radiation in but then also trap the longwave radiation, not allowing it to be released back into the atmosphere - essentially creating a blanket over the mountains which dampened the surface snow on all aspects. We may see this phenomenon again today if clouds filter in.

Today's advisory is written with Aleph Johnston-Bloom, Executive Director of the Alaska Avlanche School.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 34  56 
Summit Lake (1400') 32  12 
Alyeska Mid (1700') 35  32 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 28  var   14
Seattle Ridge(2400') 29  var    18 

 

 

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

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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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