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October 13th-14th Severe Event


Hvward

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Models continue to hint of an upper level low moving over Dixie Alley Monday-Tuesday providing sufficient forcing and a strong LLJ that will aid severe development.   

 

06z GFS showing strong upper level winds +90kt as the low cuts off over SE Kansas.

 

 

GFS_3_2014101106_F60_TMPC_500_MB.png

 

 

And continued strong vertical velocities throughout the day Tuesday giving GA and parts of SE a decent shot at severe storms. 

 

GFS_3_2014101106_F78_VVELD_500_MB.png

 

 

CAPE increase over GA & SC through Tuesday afternoon with upper level shear also in place.  These storms should be picturesque with the amount of shear present.

 

GFS_3_2014101106_F84_CAPE_SURFACE.png

 

GFS_3_2014101106_F84_SHRM_500_MB.png

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The sounding from various cities in Mississippi and Alabama are very impressive.  This has the potential to be a widespread damaging wind event...considering the winds at the 850 mbar level are nearing 70 kts.  Won't take much for those to make it to the surface in some of the storms.  Effective shear values of 45-55 kts and 0-6km helicity values of 400-500 are very impressive for October.  The tornado threat appears to be increasing as well for Mississippi/Tennesee/Alabama possibly nosing into Kentucky.    

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Once again NW GA looks to be hit in the AM. Anyone think that the system will weaken substantially overnight Monday and into Tuesday morning, or will the loss of daytime heating not have a major effect?

I do expecting a weakening squall line further east, but the strong southerly winds and high moisture content shouldn't allow the boundary layer to decouple.  There should be enough instability even into the overnight hours to support a squall line further east.    

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I think the timing of this has slowed just enough to where areas of North GA and the Carolinas could get on the action Tuesday afternoon closer to peak heating...not sure just how much surface instability will be available but dynamics are very...very impressive.

 

For Western North Carolina, it seems in the past decade that everytime we have a dynamic storm in place, some surface wedge forms out in front of it...and this time around the same will be happening. I think given how 850 winds are going to veer to SE tomorrow, the CAD will be harder to break than the models are indicating...I guess we'll see just how strong that LLJ becomes on Tuesday because there is also the potential that the LLJ bust into the surface wedge helping it break down.

 

I also think rainfall potential for the Apps could reach 3+ inches in some of the favored regions (NW Burke, Western McDowell, NW Rutherford, Henderson, Transylvania Counties...) and if you want to include today's and tomorrow's pre-frontal activity, wouldn't be a huge shock to see some 5-6 inch totals at one or two places. The Southeast flow overrunning the wedge on Monday might sneak up and provide some higher totals before the main linear feature arrives on Tuesday.

 

All in all...this storm system looks to be shaping up as a really good one for a majority of the Southeast US.

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I think the timing of this has slowed just enough to where areas of North GA and the Carolinas could get on the action Tuesday afternoon closer to peak heating...not sure just how much surface instability will be available but dynamics are very...very impressive.

For Western North Carolina, it seems in the past decade that everytime we have a dynamic storm in place, some surface wedge forms out in front of it...and this time around the same will be happening. I think given how 850 winds are going to veer to SE tomorrow, the CAD will be harder to break than the models are indicating...I guess we'll see just how strong that LLJ becomes on Tuesday because there is also the potential that the LLJ bust into the surface wedge helping it break down.

I also think rainfall potential for the Apps could reach 3+ inches in some of the favored regions (NW Burke, Western McDowell, NW Rutherford, Henderson, Transylvania Counties...) and if you want to include today's and tomorrow's pre-frontal activity, wouldn't be a huge shock to see some 5-6 inch totals at one or two places. The Southeast flow overrunning the wedge on Monday might sneak up and provide some higher totals before the main linear feature arrives on Tuesday.

All in all...this storm system looks to be shaping up as a really good one for a majority of the Southeast US.

Lapse rates and CAPE values look lower the farther east you go due to extensive cloud cover. Thus instability will be much lower than places to the west. Winds aloft are very strong, so damaging winds are possible with the weakening squall line. The slow movement won't necessarily help chances for higher severe probabilities.

PWATs are going to be abnormally high...will have to watch for heavy rain in some of the areas the see repeat rain due to the slow movement of the squall line.

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Lapse rates and CAPE values look lower the farther east you go due to extensive cloud cover. Thus instability will be much lower than places to the west. Winds aloft are very strong, so damaging winds are possible with the weakening squall line. The slow movement won't necessarily help chances for higher severe probabilities.

PWATs are going to be abnormally high...will have to watch for heavy rain in some of the areas the see repeat rain due to the slow movement of the squall line.

How does the threat look for us down here?
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How does the threat look for us down here?

The main lift will be more to the north of South Georgia.  I don't see the significant threat like areas further to the west and north.  Expect a decaying, broken squall line for South Georgia, but low level jet will be 30-40 kts across your area, so those winds could make it to the surface in the heavier storms.  Only caveat may be some convection along the Gulf Coast, which may cause a cut off of some of the low level moisture immediately inland and weaken the storms.    

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Mainly for areas such as Mississippi, Alabama, and Tennessee.  

 


...MID-SOUTH/LOWER-MIDDLE MS VALLEY/TN VALLEY/OH VALLEY...
THE POTENTIAL EXISTS FOR A REGIONAL SEVERE WEATHER EVENT ON MONDAY
INCLUDING CORRIDORS OF DAMAGING WINDS AND SOME TORNADOES...INCLUDING
A FEW POTENTIALLY STRONG...PARTICULARLY ACROSS THE MID-SOUTH AND
LOWER/MIDDLE MS RIVER VALLEY TO TN VALLEY.
WHILE A HIGHER-END SLIGHT
RISK /ENHANCED SLIGHT EQUIVALENT/ WILL CURRENTLY BE
MAINTAINED...PORTIONS OF THE REGION MAY WARRANT A MODERATE RISK
UPGRADE IN DAY 1 OUTLOOKS.

 

 

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We're starting to get a better handle on when storms may roll through Tuesday morning and will likely affect your morning commute. Still some doubt on how strong they will be when they get here but we could see wind gusts to 60 mph as well as very heavy rain with flash flooding possible. Please check the latest forecasts and conditions closely! www.weather.gov/atlanta

10389351_879171162095647_773097059572259

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I thought this was supposed to get into NC on Tuesday, but now looks like it will be Wednesday. 

 

May get some activity on Tuesday, ahead of the main stuff.  Here's a portion of the AFD from Raleigh:

 

SEVERE WX: DEEP-LAYER SHEAR WILL INCREASE FROM THE WEST TUE

AFTERNOON...WITH SUPERCELL COMPOSITE VALUES PROGGED AS HIGH AS 4-6

IN THE WESTERN PIEDMONT BY 00Z WED AND A POTENTIAL FOR ENHANCED LOW-

LEVEL SHEAR SHOULD REMNANTS OF THE CAD WEDGE PERSIST THROUGH LATE

TUE AFTERNOON. WITH THE ABOVE IN MIND...AN ISOLD SUPERCELL CAPABLE

OF PRODUCING DAMAGING WINDS OR A TORNADO WILL BE POSSIBLE LATE TUE

AFTERNOON INTO TUE NIGHT. -VINCENT

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...

AS OF 250 PM MONDAY...

SEVERAL BANDS OF CONVECTION WILL LIKELY BE ONGOING EARLY WEDNESDAY

AND WILL CONTINUE UNTIL THE COLD FRONT PUSHES SLOWLY THROUGH THE

REGION LATE WEDNESDAY AND WEDNESDAY NIGHT. THE TRENDS

CONCERNING THE TIMING OF THE COLD FRONTAL PASSAGE CONTINUE TO BE A

A BIT SLOWER... THEREFORE THE THREAT OF AT LEAST SOME SEVERE WEATHER

AND LOCALLY HEAVY RAIN WILL PERSIST UNTIL LATE WEDNESDAY (OR UNTIL

THE COLD FRONT PASSES). POP WILL DECREASE FROM WEST TO EAST LATE

WEDNESDAY. HIGHS SHOULD RANGE IN THE 60S NW INTO THE MID 70S SE.

 

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May get some activity on Tuesday, ahead of the main stuff.  Here's a portion of the AFD from Raleigh:

 

SEVERE WX: DEEP-LAYER SHEAR WILL INCREASE FROM THE WEST TUE

AFTERNOON...WITH SUPERCELL COMPOSITE VALUES PROGGED AS HIGH AS 4-6

IN THE WESTERN PIEDMONT BY 00Z WED AND A POTENTIAL FOR ENHANCED LOW-

LEVEL SHEAR SHOULD REMNANTS OF THE CAD WEDGE PERSIST THROUGH LATE

TUE AFTERNOON. WITH THE ABOVE IN MIND...AN ISOLD SUPERCELL CAPABLE

OF PRODUCING DAMAGING WINDS OR A TORNADO WILL BE POSSIBLE LATE TUE

AFTERNOON INTO TUE NIGHT. -VINCENT

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY/...

AS OF 250 PM MONDAY...

SEVERAL BANDS OF CONVECTION WILL LIKELY BE ONGOING EARLY WEDNESDAY

AND WILL CONTINUE UNTIL THE COLD FRONT PUSHES SLOWLY THROUGH THE

REGION LATE WEDNESDAY AND WEDNESDAY NIGHT. THE TRENDS

CONCERNING THE TIMING OF THE COLD FRONTAL PASSAGE CONTINUE TO BE A

A BIT SLOWER... THEREFORE THE THREAT OF AT LEAST SOME SEVERE WEATHER

AND LOCALLY HEAVY RAIN WILL PERSIST UNTIL LATE WEDNESDAY (OR UNTIL

THE COLD FRONT PASSES). POP WILL DECREASE FROM WEST TO EAST LATE

WEDNESDAY. HIGHS SHOULD RANGE IN THE 60S NW INTO THE MID 70S SE.

 

 

 

Looks like Tuesday might be the opening act, while Wednesday is the headliner.

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Looking at the radar right now, looks like some thunderstorms are popping up along the coast on the Gulf off the coast of Florida. Is that going to rob us of moisture for this event? 

 

Only if it can't heal in time...

 

On a serious note, the NAM seems to be getting it's act together, precip amounts have only went up on the last few runs. I foresee a lot of flood watches east of the mountains.

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I'm looking at doing a bit of chasing later tomorrow if things set up right within a reasonable range. At the moment I am thinking heading south to southeast from here would give me the best chance. Can't really know until things start developing.  Hoping to get some interesting video.

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Here's the latest thinking on the timing of the line of thunderstorms moving into Georgia Tuesday morning. It still looks like wind gusts to 60 mph and heavy rainfall will be the foremost threats, although isolated tornadoes cannot be ruled out. Stay updated at www.weather.gov/atlanta.

10688056_879739472038816_391019268292952
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Folks,

 I've been asked how it is looking for Atlanta and just north for tomorrow with regard to severe potential. This involves kids going to school. Does anyone here have much confidence in how bad or not so bad it will get in the Atlanta-Sandy Springs corridor between sunrise and the afternoon? TIA.

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