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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
1142 AM EDT TUE SEP 1 2015

...FORECAST UPDATE...
ISSUED AT 1142 AM EDT TUE SEP 1 2015

THE CONVECTIVE COMPLEX ON THE WESTERN FLANK OF AN UPPER LOW WILL 
CONTINUE TO WEAKEN OVER THE WABASH RIVER VALLEY OVER THE NEXT FEW 
HOURS. AN OUTFLOW BOUNDARY HAS KICKED TO THE SOUTH OF THIS COMPLEX, 
EVIDENT ON VISIBLE SATELLITE/RADAR. WE'LL WATCH FOR CONVERGENCE 
ALONG THIS BOUNDARY THIS AFTERNOON AS IT SLIDES INTO OUR SOUTHERN IN 
COUNTIES, ALTHOUGH MOISTURE DOES NOT LOOK TO BE VERY IMPRESSIVE. 
WILL KEEP THE 20 PERCENT CHANCE GOING IN SOUTHERN INDIANA, DRY
SOUTH OF THE OHIO RIVER. OTHER PORTIONS OF THE FORECAST LOOK GOOD
AS WELL WITH TEMPS ALREADY IN THE LOW 80S IN MOST SPOTS. THEY
SHOULD TOP OUT AROUND 90.

HAVE JUST BEEN NOTIFIED OF ANOTHER AIR QUALITY ALERT IN THE 
LOUISVILLE METRO FOR WEDNESDAY, SO WILL BE UPDATING THAT PRODUCT 
SHORTLY.

.SHORT TERM (NOW THROUGH WEDNESDAY)...
ISSUED AT 302 AM EDT TUE SEP 1 2015

PERSISTENCE IS THE KEY TO THE SHORT TERM FORECAST AS BOTH THE UPPER 
LEVEL AND SURFACE WEATHER PATTERN REMAIN LARGELY UNCHANGED FROM THE 
PAST FEW DAYS. THE DOG DAYS OF SEPTEMBER ARE UPON US IT SEEMS.

LIGHT/VARIABLE WINDS COMBINED WITH SOME BOUNDARY LAYER MOISTURE THIS 
MORNING IS PRODUCING PATCHY FOG ACROSS THE FAVORED LOCATIONS. THIS 
SHOULD BURN OFF QUICKLY AFTER SUNRISE. PLAN ON ANOTHER SEASONABLY 
WARM AND MUGGY DAY AS READINGS TOP OUT RIGHT AROUND 90 UNDER MOSTLY 
TO PARTLY SUNNY SKIES. A WEAK UPPER LEVEL SHORTWAVE SPINNING OVER 
CENTRAL INDIANA WILL BE THE FOCUS FOR A STRAY SHOWER OR STORM THIS 
AFTERNOON. MODELS SHOW THIS FEATURE DROPPING SOUTH A BIT...SO WILL 
CONTINUE TO CARRY A SLIGHT CHANCE ACROSS SOUTHERN INDIANA DURING 
PEAK HEATING. 

LOOK FOR ANOTHER MUGGY NIGHT WITH PATCHY FOG POSSIBLE AND LOWS RIGHT 
AROUND 70. WEDNESDAY WILL BE A CARBON COPY...MAINLY DRY CONDITIONS 
WITH HIGHS NEAR 90.

.LONG TERM (WEDNESDAY NIGHT THROUGH MONDAY)...
ISSUED AT 323 AM EDT TUE SEP 1 2015

IN THE LONG TERM PERIOD, THE LATEST MODELS CONTINUE INDICATE A 
HIGHLY AMPLIFIED UPPER LEVEL PATTERN.  THIS IS ONE IS A BIT 
DIFFERENT THAT THE ONE THAT WE'VE TYPICALLY SEEN THIS SUMMER IN THAT 
THE EASTERN U.S. WILL BE UNDER A DEVELOPING RIDGE WHILE UPPER 
TROUGHING REMAINS OUT TO THE WEST.  HIGH PRESSURE AT THE SURFACE 
BENEATH THE UPPER LEVEL RIDGE WILL KEEP PRECIPITATION SUPPRESSED 
ACROSS OUR REGION WITH TEMPERATURES REMAINING NEAR SEASONAL NORMALS.

WITH THE DEVELOPING RIDGE OVER THE EASTERN U.S., WE'LL HAVE TO KEEP 
A WATCH FOR SEVERAL WAVES THAT WILL MIGRATE AROUND THE PERIPHERY OF 
THE RIDGE.  PREVIOUS MODEL RUNS HAD SEVERAL WEAK DISTURBANCES MOVING 
NEAR THE REGION.  HOWEVER, THE LATEST RUNS HAVE STRENTHENED THE 
RIDGE SOMEWHAT AND THESE DISTURBANCES LOOK TO HAVE LESS OF AN IMPACT 
ON OUR WEATHER.  HOWEVER, WE COULD SEE SOME ISOLATED STORMS AS CLOSE 
AS SOUTHEASTERN IN, OR SOUTHWEST OHIO THURSDAY AFTERNOON/EVE.

AS WE HEAD INTO THE HOLIDAY WEEKEND, THE UPPER LEVEL RIDGE LOOKS TO 
REMAIN IN PLACE ACROSS THE EASTERN US.  THE GLOBAL DETERMINISTIC AND 
ENSEMBLE MODELS DO HINT AT A BIT OF UPPER LEVEL TROUGHING DEVELOPING 
OVER THE SOUTHEASTERN US BY SUNDAY.  WITH AN AREA OF SURFACE HIGH 
PRESSURE TO THE EAST, A SOUTHERLY FLOW MAY GET RE-ESTABLISHED AND 
ATTEMPT TO TRANSPORT DEEPER GULF MOISTURE BACK INTO THE REGION.  
THERE REMAINS CONSIDERABLE SPREAD IN THE ENSEMBLES REGARDING THE 
EVOLUTION OF THE PATTERN AT THAT TIME PERIOD.  THUS, A PERSISTENCE 
FORECAST OF DRY CONDITIONS LOOKS MORE LIKELY AT THIS POINT.  
HOWEVER, A STRONGER SIGNAL SUGGESTS THAT MOISTURE MAY BE PLENTIFUL 
ENOUGH BY MONDAY TO SPARK A STRAY SHOWER OR STORM...ESPECIALLY 
ACROSS SOUTHERN KY.  THIS WILL BE SOMETHING TO WATCH OVER THE COMING 
DAYS.

HIGHS DURING THE THE PERIOD WILL RANGE FROM THE UPPER 80S IN THE 
NORTH TO THE LOWER 90S IN THE SOUTH.  OVERNIGHT LOWS WILL GENERALLY 
RANGE FROM THE UPPER 60S TO THE LOWER 70S.  IT IS INTERESTING TO 
NOTE THAT SOME OF THE RAW MODEL GUIDANCE CONTINUES TO SUGGEST THAT 
WE'LL SEE MID 90S BY LATE WEEK AND INTO THE WEEKEND.  HOWEVER, 850 
TEMPS ARE NOT WARMING MORE THAN 1-2 DEGREES OVER WHAT WE'RE SEEING 
RIGHT NOW...AND WE'VE BEEN HARD PRESSED TO HIT 90 IN THE LAST FEW 
WEEKS.  SHOULD ALSO NOTE THAT THE MODELS HAVE BEEN EXHIBITING A WARM 
BIAS ON SURFACE TEMPERATURES.  THE CONSALL BLENDS AND THE BIAS-
CORRECTED MODELS HAVE BEEN WHIPPING UP ON THE DETERMINISTIC 
SOLUTIONS HERE. THUS, HAVE STUCK CLOSE TO THE SUPERBLEND GUIDANCE 
WHICH IS VERY SIMILAR TO PREVIOUS FORECAST.  SOME SLIGHTLY COOLER 
READINGS ARE POSSIBLE BY LATE IN THE PERIOD DUE TO INCREASED CLOUD 
COVER AND ISOLATED CONVECTION, IF THE SOUTHERN GULF MOISTURE GETS UP 
INTO THE REGION.

&&

.AVIATION (12Z TAF UPDATE)...
ISSUED AT 640 AM EDT TUE SEP 1 2015

SOME LIGHT FOG WILL CONTINUE AT BWG THROUGH ABOUT 12-13Z...THEN PLAN 
ON VFR CONDITIONS AT ALL THE TAF SITES THROUGH THE PERIOD. WEAK 
UPPER LEVEL SYSTEM SPINNING OVER INDIANA MAY SPARK SHOWERS/STORMS 
LATER TODAY BUT THOSE SHOULD STAY WELL NORTH OF SDF/LEX. 
OVERALL...WINDS WILL BE LIGHT AND VARIABLE WITH HIGH PRESSURE NEARLY 
OVERHEAD. LOOK FOR PATCHY LIGHT FOG AGAIN LATE TONIGHT AT BWG...IN 
THE TYPICAL 9-13Z WINDOW.

&&

.LMK WATCHES/WARNINGS/ADVISORIES...
KY...NONE.
IN...NONE.
&&

$$

UPDATE.........BJS
SHORT TERM.....ZBT
LONG TERM......MJ
AVIATION.......ZBT

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