191 FXUS64 KOHX 180730 AFDBNA AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE NASHVILLE TN 230 AM CDT WED JUL 18 2001 WELL...AT 0520Z WE HAVE A RAPIDLY DYING MCS OVER IL...AND IS THE MAIN STORY AT THE MOMENT. THIS COMPLEX FIRED UP DURING THE MID TO LATE AFTERNOON ACROSS NRN IL...AND IS SLOWING MOVING S-SE. OTHER MCS OF INTEREST...IS CURRENTLY EXPANDING OVER THE ERN PORTIONS OF THE HOOSIER STATE TO THE WRN PORTIONS OF THE BUCKEYE STATE. H8 LOW LEVEL JET OF 20-30 KTS IS FEEDING COMPLEX FROM MO/IL...INTO THE LEADING EDGE OF FRONTAL BOUNDARY OVER NRN IN/OH. A 3RD MCS OVER ERN NE AND IA WILL RIDE THE RIDGE AND TAKE THE NESTEA PLUNGE OVER IL...AND WILL ALSO HAVE TO BE WATCHED. COPIOUS AMOUNTS OF LIGHTNING IN THIS ONE. SYNOPTICALLY...TROUGHS DOMINATE BOTH THE EAST AND WEST COAST WHILE SUBTROPICAL RIDGE ENCOMPASSES THE PLAINS. A 558M LOW IS CENTERED OVER ALBERTA PROVINCE AND TROUGH EXTENDS THROUGH THE BITTERROOT RANGE INTO CA. LARGE ANTICYCLONE CENTER OVER OK AND TX...ALLOWING CLASSIC JULY NW FLOW ALOFT...AND RESULTANT MCS(S). THE MAIN DIFFERENCE IN THE MODELS IS ONCE AGAIN WITH POPS AND QPF. I FOUND 2 DIFFERENCES WITH THE MODELS IN OUR NECK OF THE WOODS. THE 1ST IS THE NGM BEING A LITTLE OVERDONE ON THE H5 RIDGE... AND SECONDLY THE AVN SEEMS TO BE HAVING SOME CONVECTIVE FEEDBACK PROBLEMS OVER IA/IL LATER TODAY AND INTO THE UPPER MS VALLEY WEDNESDAY NIGHT INTO THURSDAY MORNING. BOTH ETA AND NGM FRH DATA PEGGING BNA PRECIP ON THURSDAY...AND ETA HAS PRECIP FOR TONIGHT.... WHEREAS THE NGM IS BONE DRY. SERIES OF SHORTWAVES SLIDING OFF THE RIDGE...INTERSECTING A INCREASINGLY UNSTABLE AIRMASS WILL BE THE CRUX FOR LATE AFTERNOON TSRA ACROSS IL. MID LEVEL THICKNESSES TAKE THIS DOWN INTO THE CWA WEDNESDAY NIGHT. ETA MODEL SOUNDINGS INCREASE BNA CAPE TO 2200 J/KG...LIFTED INDICES BETWEEN -3 AND -5 AND A K INDEX IN THE MID 30S. APPEARS TO BE A SURFACE TROUGH STRETCHED ACROSS CENTRAL IL TOO...SO THERE SHOULD BE ENOUGH FORCING FROM TROUGH...LOW LEVEL JET OF 20 KTS...AND SHORT WAVE TO INITIATE CONVECTION BETWEEN PIA-DEC-SLO AND EVENTUALLY BECOME A MCS WEDNESDAY NIGHT. WITH PRECIPITABLE WATER VALUES NEARING 2 INCHES...HEAVY RAIN IS THE MAIN THREAT WED. NIGHT INTO THU. ETA DROPS ANOTHER SHORT WAVE FROM IL INTO CWA THURSDAY NIGHT TOO. CHANGES FROM THE PREVIOUS FORECAST WILL BE THE INTRODUCTION OF SCATTERED POPS WEDNESDAY NIGHT...AND I AM SERIOUSLY CONTEMPLATING GOING LIKELY POPS IN THE NORTH. NCEP LEAD FORECASTER DAY 1 QPF LOOKS VERY REASONABLE...WITH BETWEEN AND A QUARTER AND A HALF AN INCH. ITS NOW 145 AM...OLD MCS HAS A FEW NEW CELLS THAT HAVE REGENERATED AND STORMS IN N CENTRAL KY ARE MOVING SE AT 20 AND WILL AFFECT AREAS EAST OF NASHVILLE BETWEEN 4 AND 7 AM IF THEY HOLD TOGETHER... SO MAY HAVE TO MAKE A THIS MORNING GROUP TO ADDRESS THIS. ZONES WILL BE ISSUED AT PRESS TIME...AS TO WAIT TO THE VERY LAST MINUTE TO SEE THE LASTEST RADAR AND SATELLITE SHOTS TO SEE WHAT THE CONVECTION IS DOING. COORDINATED WITH SDF...PAH...JKL...MEM. PRELIMINARY NUMBERS FOR COORDINATION PURPOSES ONLY BNA 091/075 089/074 3654 CSV 087/069 087/068 4554 .BNA...NONE. JDG