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000
FXUS63 KJKL 161446
AFDJKL

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
1046 AM EDT THU MAY 16 2013

.UPDATE...
ISSUED AT 1046 AM EDT THU MAY 16 2013

CONVECTION ASSOCIATED WITH THE SURFACE FRONT OVER OH HAS MADE LITTLE
SOUTHWARD PROGRESS THIS MORNING. HOWEVER...A BOUNDARY FROM SOUTHERN
OH CONVECTION HAS MOVED SOUTH INTO KY...AND THIS IS INTERACTING WITH
ENERGY ROTATING NORTHEAST FROM THE MID LEVEL LOW OVER OK. SHOWERS AND
THUNDERSTORMS HAVE BEEN DEVELOPING FROM SDF EAST TO SOUTH OF LEX.
THE 12Z HRRR IS HANDLING THIS FAIRLY WELL...AND THE 12Z NAM IS ALSO
SHOWING THIS. BASED ON CURRENT ANALYSIS...TRENDS AND LATEST MODEL
GUIDANCE HAVE MADE ADJUSTMENTS TO PRECIPITATION CHANCES FOR TODAY. HAVE
INCREASED COVERAGE IN THE CENTRAL PART OF THE AREA TO SCATTERED WITH
A 30 PERCENT CHANCE AND HAVE DECREASED THE PROBABILITY IN THE FAR
SOUTH FROM 40 PERCENT TO 30 PERCENT. WILL CONTINUE TO CARRY THE
HIGHEST SHOWER AND THUNDERSTORM CHANCES IN THE NORTH.

UPDATE ISSUED AT 857 AM EDT THU MAY 16 2013

CLOUDS HAVE INCREASED QUICKLY THIS MORNING...AND HAVE UPDATED THE
NDFD AND ZFP TO REFLECT THIS. MOSTLY CLOUDY SKIES NOW FORECAST ACROSS
THE ENTIRE AREA FOR TODAY. HRRR IS HANDLING CURRENT CONVECTION FAIRLY
WELL. 11Z HRRR POINTS TOWARDS A NORTH TO SOUTH RAIN PROBABILITY
CHANCE THIS AFTERNOON...WITH BEST CHANCE IN THE NORTH. WILL TAKE A
LOOK AT INCOMING 12Z DATA FOR ANY POSSIBLE UPDATES TO THE RAIN
PROBABILITIES FOR THIS AFTERNOON.

&&

.SHORT TERM...(TODAY THROUGH FRIDAY)
ISSUED AT 253 AM EDT THU MAY 16 2013

THERE ARE TWO MAIN INGREDIENTS TO THIS FORECAST WHICH INDIVIDUALLY
AND COLLECTIVELY ADD SOME DIFFICULTY TO THE FORECAST. THERE IS A COLD
FRONT SOUTH OF THE GREAT LAKES WHICH IS SAGGING TO THE SOUTH. THERE
IS ALSO AN UPPER LOW OVER OKLAHOMA EMBEDDED IS A WEAKER SOUTHERLY
STREAM. THESE TWO SYSTEMS ARE BOTH GOING TO BE EFFECTING THE WEATHER
OVER THE AREA OVER THE NEXT TWO DAYS. AT 230 AM THERE WAS A LINE OF
SHOWER AND THUNDERSTORMS WHICH EXTENDED FROM SOUTHWEST PENNSYLVANIA AND
THEN PASSED SOUTH OF COLUMBUS AND THEN ACROSS DAYTON. THIS SYSTEM
WILL BE SAGGING TO THE SOUTH. THE BIG QUESTION IS HOW FAR SOUTH WILL
THE FRONT MOVE. THE NAM STALLS THIS FRONT OUT ALONG THE OHIO RIVER
VALLEY. AS A RESULT...KEPT THE BEST CHANCE FOR RAIN TODAY AND
TONIGHT NORTH OF I 64 IN THE BLUEGRASS. THE MODELS ARE ALSO
GENERATING SOME ENERGY OUT AHEAD OF THE UPPER LOW WHICH WILL BE
MOVING TO THE EAST THE AREA SOUTH OF I 64 WILL BE IN THE GENERALLY
UNSTABLE WARM SECTOR TODAY AND TONIGHT WITH SOME ENERGY SPINNING
AROUND THE UPPER LOW WHICH MAY MOVE INTO THE AREA LATER TODAY. THIS
IS MOST LIKELY GOING TO EFFECT THE AREA SOUTH OF THE HAL ROGERS
PARKWAY. SO THERE IS A SLOT ACROSS THE CENTRAL PORTION OF EASTERN
KENTUCKY WHICH SHOULD BE SOUTH OF THE INFLUENCE OF THE FRONT AND
NORTH OF THE INFLUENCE OF THE UPPER LOW. THE ONE THING THAT IS A BIT
OF A WILD CARD IS IF THE THUNDERSTORMS TO THE NORTH ARE ABLE TO
CREATE A COLD POOL TODAY WHICH PROPAGATES SOUTH ACROSS EASTERN
KENTUCKY. THE NAM BUFFER SOUNDING HAS A LIFTED INDEX OF AROUND -5
THIS AFTERNOON...SO IF A COLD POOL DOES MOVE INTO THE AREA...THERE
WILL BE PLENTY OF INSTABILITY TO KEEP IT GOING. THE SCENARIO IS NOT
IN THE FORECAST...HOWEVER BEARS WATCHING.THERE SHOULD BE PLENTY OF
CLOUDS TODAY...HOWEVER THE LOWER LAYERS ARE FAIRLY DRY AND IT SHOULD
TAKE A WHILE TO BE ABLE TO MOISTEN THEM UP ENOUGH FOR THE RAIN TO
REACH THE GROUND. THE TEMPERATURES WILL BE SO DEPENDENT ON HOW
EXTENSIVE THE SHOWERS WILL BE TODAY. WENT A BIT WARMER THAN THE MODEL
CONSENSUS AND BLENDED CLOSER TO THE WARMER NAM MOS FOR TODAY AND
TOMORROW.

.LONG TERM...(FRIDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 253 AM EDT THU MAY 16 2013

MODE LS ARE IN FAIR AGREEMENT...BETTER WITH RELATIVELY SLOW BUT
PROGRESSIVE UPPER AIR PATTERN THAN WITH SURFACE FEATURES. EXTENDED
STARTS OUT WITH AN OPEN WAVE TRACKING EASTWARD ACROSS THE OHIO/TN
VALLEY REGIONS THROUGH THE WEEKEND. SHORTWAVE RIDGE THEN TRANSITS
THE REGION MONDAY BEFORE SLOW MOVING LOW PRESSURE SYSTEM OVER THE
NORTH CENTRAL PLAINS SHIFTS INTO THE MIDWEST...OR GREAT LAKES BY THE
END OF THE FORECAST WINDOW. WE FALL UNDER A SOUTHWEST FLOW REGIME
ALOFT DURING THE INTERIM. ECMWF...WITH SUPPORT FROM THE CANADIAN
APPEARS MORE ORGANIZED AND FURTHER SOUTH WITH THE UPPER LOW MOVING
OUT OF THE PLAINS AND INTO THE MIDWEST VERSUS THE GFS WHICH KEEPS
THE UPPER LOW UP OVER THE NORTHERN TIER. MODELS DIVERGE EVEN MORE
SIGNIFICANTLY JUST BEYOND THE END OF THE FORECAST PERIOD. TENDENCY
IS TO LEAN TOWARDS THE TYPICALLY MORE ACCURATE...RELIABLE ECMWF WITH
RESPECT TO THE EVOLUTION OF THE UPPER AIR PATTERN.

AT THE SURFACE...AGAIN MODELS DIFFER CONSIDERABLY ON THE EVENTUAL
POSITION SOUTHERN EXTENT OF SURFACE COLD FRONTAL BOUNDARY ACROSS THE
OHIO VALLEY EARLY IN THE FORECAST. THE NAM/GFS BRINGS THE BOUNDARY
AS FAR SOUTH AS AN IND TO DAY LINE LATE THIS AFTERNOON AND/OR EARLY
FRIDAY MORNING RESPECTIVELY. THE ECMWF BRINGS THE BOUNDARY SOUTHWARD
TO BETWEEN DAY AND CVG BY EARLY SATURDAY MORNING...APPARENTLY WITH
SUPPORT FROM THE UPPER LEVEL WAVE THAT PUSHES THROUGH THE REGION.
END RESULT IS THAT THE BOUNDARY NEVER REALLY SEEMS TO MAKE IT AS FAR
SOUTH AS THE OHIO RIVER...IN A TRUE SUMMERTIME LIKE FASHION. THIS
DOES NOT BODE WELL FOR THE OPPORTUNITY OF RAIN UNLESS CONVECTION
ALONG THE FRONTAL BOUNDARY BECOMES MORE ORGANIZED AND MANAGES TO
MAKE A SURGE SOUTHWARD INTO OUR AREA. BEST OPPORTUNITY FOR THIS...
OR JUST SHOWER AND THUNDERSTORM ACTIVITY IN GENERAL WILL COME AS THE
UPPER LEVEL WAVE OR DISTURBANCE GRADUALLY SHIFTS THROUGH THE REGION
SATURDAY AND SUNDAY. TRENDED DRIER SUNDAY NIGHT THROUGH MONDAY NIGHT
WITH UPPER LEVEL RIDGING BUILDING INTO THE AREA. THREAT OF SHOWERS
AND THUNDERSTORMS INCREASE AGAIN TOWARDS THE END OF THE FORECAST
WINDOW...TUESDAY NIGHT AND/OR WEDNESDAY AND BEYOND AS SYSTEM MORE
THAN LIKELY MAKES A MOVE TOWARDS OUR AREA OUT OF THE NORTH CENTRAL
PLAINS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 725 AM EDT THU MAY 16 2013

VFR CONDITIONS WILL HOLD THROUGH THE TAF FORECAST PERIOD. A THREAT
OF THUNDERSTORMS ARE POSSIBLE THIS AFTERNOON WITH THUNDERSTORMS
MOVING FROM THE NORTH IN THE JKL AREA AND FROM THE SOUTH FOR LOZ AND
SME. THERE IS ONLY AND SLIGHT CHANCE AT JKL AND A CHANCE AT SME AND
LOZ. THERE IS TOO MUCH UNCERTAINTY TO GO WITH A PREVAILING
THUNDERSTORM GROUP AS THE THUNDERSTORMS COULD STAY NORTH OR SOUTH AND
MAY NOT IMPACT THE TAF SITES.


&&

.JKL WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...SBH
SHORT TERM...JJ
LONG TERM...RAY
AVIATION...JJ