Severe Thunderstorm Warning 91, NWS Nashville, TN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NASHVILLE TN
250 PM CDT WED JUN 6 2001

THIS FORECAST PACKAGE IS FULL OF UNCERTAINTIES...ESPECIALLY
REGARDING TIMING FOR GREATEST LIKELIHOOD OF THUNDERSTORMS. MODELS
ARE USEFUL FOR THE OVERALL PATTERN...BUT DETAILS ARE NOT RELIABLE.
MAIN CONCERN THROUGH THE NEXT COUPLE OF DAYS WILL BE HEAVY RAINFALL
THREAT AS PERIODS OF SHOWERS AND THUNDERSTORMS DEVELOP IN AN
INCREASINGLY TROPICAL AIR MASS. PRECIPITABLE WATER VALUES
FROM 1.5-2.0 INCH WILL BE COMMON ACCORDING TO MODELS...AND EVEN
HIGHER IN OUR SOUTHERN COUNTIES. THE POTENTIAL FOR HEAVY RAIN WILL
BE MENTIONED IN THE ZONE FORECASTS. FLASH FLOOD WATCHES MAY NEED TO
BE CONSIDERED BY UPCOMING SHIFTS. FOR NOW...TIMING AND OCCURRENCE IS
FAR TOO UNCERTAIN. BEST GUESS FOR FLOODING ISSUES...SOUTHERN HALF OF
MID TN LATE AFTERNOON THURSDAY AND THURSDAY NIGHT. SOUTHERN ZONES
HAVE ALREADY HAD WATER PROBLEMS WITHIN THE PAST WEEK AND ARE MOST
RIPE FOR AGGRAVATION.

ON THE SURFACE MAP...TROPICAL LOW WAS OVER LFK IN EAST TX.
PERSISTENT BOUNDARY EXTENDED FROM THE MID ATLANTIC...ACROSS THE OHIO
VALLEY TO KS. A WAVE WAS ALONG THE FRONT WITH A TROF EXTENDING FROM
SOUTH IN TO THE MO BOOTHEEL. ONE BAND OF THUNDERSTORMS FROM NORTH GA
TO THE CUMBERLAND PLATEAU...BEING ENHANCED BY TERRAIN. ANOTHER AREA
OF SHOWERS AND THUNDERSTORMS COVERED NORTHWEST MID TN INTO WEST KY.
THIS AREA WAS BEING SUPPORTED BY THE SURFACE TROF.

FOR TONIGHT...THUNDERSTORMS WILL CONTINUE AHEAD OF THE SURFACE
TROF...AFFECTING MAINLY KY AND INTO OUR NORTHERN COUNTIES THIS
EVENING. OTHERWISE...CANNOT PIN DOWN SIGNIFICANT FEATURE FOR
ORGANIZED CONVECTION. WILL GO WITH "SCATTERED THUNDERSTORMS" WORDING
AND AROUND 40 POPS.

BEYOND TONIGHT...MODELS DIFFER GREATLY WITH QPF FIELDS. AVN MODEL
WANTS TO RUSH FRONT THROUGH THE AREA TOO QUICKLY. ETA MAY BE TOO
SLOW. LEANING TOWARD A LITTLE SLOWER PASSAGE THAN PREVIOUS FORECAST.
DO NOT SEE A BIG "PUSH" FOR THE FRONT...AND TROPICAL SYSTEM MAY SLOW
PASSAGE. IT SEEMS THAT WITH EACH SUCCESSIVE FORECAST PACKAGE WE HAVE
ADDED RAIN CHANCES TO ANOTHER PERIOD OF THE FORECAST. WELL...THAT
TREND WILL CONTINUE. HOPEFULLY THE FRONT WILL BE THROUGH THE AREA BY
THE END OF FRIDAY? WILL CARRY HIGHER THAN GUIDANCE POPS FOR
THURSDAY AND ESPECIALLY THURSDAY NIGHT WHEN VERY MOIST AIR WILL MEET
UP WITH INCREASED LOW LEVEL CONVERGENCE ALONG APPROACHING FRONT.
WILL ADD MORNING CHANCES FOR THE NORTH FRIDAY...AND ALL DAY CHANCE
ACROSS THE SOUTH.

THE WEEKEND/EXTENDED OUTLOOK WILL BRING BETTER WEATHER. ALTHOUGH
CANNOT RULE OUT A PERIOD OF SHOWERS IN THE ENTENDED AS THE REGION
WILL BE UNDER TRICKY NORTEHWEST FLOW ALOFT.

PRELIM NUMBERS...
BNA TE 069/082 067/083 063 4683
CSV TE 064/078 063/079 058 4684

.BNA...NONE.

SH