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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Graham Predeger  
Tuesday, March 22nd 2016
Created: Mar 22nd 6:28 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'
 Show the Complete North American Avalanche Danger Scale
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The Bottom Line

The avalanche danger is MODERATE above 1,000’ today.  Wet loose avalanches in steep terrain (greater than 35 degrees) will be possible to trigger and are producing enough mass to be problematic as the moist surface extends up to ridgetops in many locations around Turnagain Pass.  Cautious terrain evaluation is essential today in order to avoid being pushed into a terrain trap by wet, heavy moving snow.

Winds are unlikely to effect yesterday’s moist surface but any new snow and wind today will build in to shallow, but tender wind slabs in the alpine.  Cracks and cornices continue to warrant mention as well.  At least three new glide avalanches were observed yesterday, post-storm.


Primary Concern

Observations from the field yesterday found a moist surface up to at least 3200’ in the wake of the Sunday/ Monday warm up.  Unfortunately this wasn’t only relegated to solar aspects but shadier north aspects were harboring a moist surface as well.  The weekend storm snow is settling out rather rapidly, compressing the several inches of cooler, low-density snow (from Saturday morning) into a thin weak layer 6-16” below the surface.  In steep terrain, wet-loose snow yesterday was easy to initiate, building enough mass and momentum that it could pose a problem for a skier in consequential terrain.  These are relatively small but heavy and powerful avalanches that are difficult to escape from.  Keep this in mind as you are travelling above any terrain traps such as gullies, trees, cliffs or glide cracks.  Snowmachiners: The surface is such right now that you can entrain a significant amount of heavy wet snow as you descend.  It’ll be prudent to ‘manage’ this heavy sluff and avoid terrain traps. 

Last night was the second night in a row where temperatures did not freeze overnight below about 2,000’ making for a punchy, rotten snowpack.  If temperatures do spike again today in the afternoon or we receive significant rain on snow, it’s entirely possible that wet loose avalanches could pull out dangerous wet slabs in this mid-elevation band.

Wet loose avalanches skiers-right of Todd's run.  Eddies glide crack-complex in the background.

 

Roller balls are another good clue to a warming surface, primed for wet-loose avalanches.  


Secondary Concern

Good visibility allowed us a look around yesterday to add to a growing list of glide avalanches across the region.  The post-storm tally was 3 new glides: Penguin ridge, Skookum Valley and Seattle ridge (N. of uptrack).  As long as glide cracks continue to open up, move and release, we will stress the importance of avoiding them, which is THE ONLY WAY TO MANAGE THIS AVALANCHE PROBLEM.  Remember, this is the entire winters snowpack releasing to the ground suddenly and without warning.  Simple avoidance of glide cracks continues to be the key.

CORNICES:  We did see some active cornice shedding during the heat of the day yesterday.  Take extra precautions when travelling around cornices as they tend to break much further back on ridges than often times expected.


Additional Concern

Winds have been cranking enough in the alpine to transport any available snow into shallow wind slabs.  Likely these will be found somewhere above 3500’ today where the snow surface dries out.  2-4” of new snow forecasted and moderate easterly winds in the upper elevations today will add to existing wind slabs in the 1-2’ range.


Mountain Weather

The most notable aspect to yesterday’s weather was the warmth in the air.  40-degree temps are finally acting to melt out some of the SUV-swallowing potholes in the motorized lot at 1,000’.  Pavement is again visible!  Ridgetop temperatures spiked at 34 degrees in the afternoon on the top of Sunburst (3800’).  Just a trace of precip was measured yesterday morning before skies broke mostly sunny.  Winds were light (gusting into the 20’s) from the East before picking up overnight.

Today we can expect up to another half inch of water throughout the day with a rain/ snow line around 2,000’.  Winds will be from the east in the 20-30 mph range.  Temperatures will again be unseasonably warm in the high 30’s to low 40’s at 1,000’.

The well-developed low tracking North into the Gulf today may not influence us much tomorrow as a persistent upper level ridge looks to limit its advance onto the mainland.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 39 .2  131 
Summit Lake (1400')  39 .3   45
Alyeska Mid (1700')  37  0  n/a 109 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  30  ENE 17   49
Seattle Ridge(2400')  33  SE 18  39 

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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