Severe Thunderstorm Warning 148, NWS Jackson, KY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON KY
246 PM EDT SUN JUL 30 2000

LARGE SCALE PATTERN IS STILL VERY SLOW TO CHANGE...WITH UPPER LOW AT
12Z CENTERED A LITTLE SOUTH OF CHICAGO AND BROAD TROUGH ALIGNED
SOUTHWEST TO NORTHEAST AROUND IT. SYSTEM IS NEARLY STACKED...WITH
THE SURFACE LOW SLOWLY PIVOTING AROUND THE EAST SIDE OF IT INTO
MICHIGAN.

THE LOCAL AIR MASS IS VERY MOIST WITH PRECIPITABLE WATER RUNNING 1.5
TO 2 INCHES. OUTSIDE OF SOME BRIEF DRYING ALOFT LATE TODAY...MODELS
KEEP PRECIPITABLE WATER HIGH UNTIL AROUND MONDAY EVENING. THERE IS
LITTLE TO NO CAP TO INHIBIT CONVECTION. HOWEVER...WITH ALL THE
CLOUDS AND OCCASIONAL PRECIP...HEATING AND INSTABILITY IS LIMITED.
SO IN GENERAL...PROSPECTS FOR MORE RAIN LOOK GOOD...BUT CHANCES OF
SEVERE WEATHER OR EXCESSIVE RAIN ARE LIMITED.

THE NEXT SIGNIFICANT FEATURE TO AFFECT US SHOULD BE OVERNIGHT
TONIGHT. ALTHOUGH THE MODELS ARE NOT AN EXACT MATCH...THEY ALL HAVE
US UNDER THE RIGHT ENTRANCE REGION OF AN UPPER JET LATE TONIGHT INTO
MONDAY MORNING. AFTER THIS...IT IS HARD TO FIND ANY SIGNIFICANT
FEATURES YOU CAN "SINK YOUR TEETH INTO" TO FINE TUNE A FORECAST.
MODELS DO SHOW US BACK INTO THE RIGHT REAR QUADRANT OF THE UPPER JET
ON TUESDAY...BUT DO NOT AGREE ON POSITIONING OF DYNAMICS ASSOCIATED
WITH IT. AT THIS TIME WILL BASE FORECAST FROM MONDAY AFTERNOON
THROUGH TUESDAY ON DIURNAL EFFECTS.

WITH THIS IN MIND...WILL GO WITH LIKELY POPS TONIGHT WITH UPPER
SUPPORT MOVING IN LATE. WILL GO WITH LIKELY POPS ON MONDAY DUE TO
LINGERING UPPER SUPPORT...FOLLOWED BY DAYTIME
WARMING/DESTABILIZATION. WILL GO DOWN TO LOW CHANCE POPS AS
SUGGESTED BY NGM MOS ON MONDAY NIGHT...FOLLOWED BY HIGH CHANCE POPS
ON TUESDAY WITH DESTABILIZATION AND VIRTUALLY NO CAP EXPECTED.

FOR TEMPS...NGM MOS AND AVN MAV NUMBERS DO NOT VARY BY MORE THAN A
DEGREE FOR LOWS AND WILL GO WITH THEM. NGM MOS HIGHS (OUTSIDE OF
LEX) ARE 2 OR 3 DEGREES ABOVE AVN MAV. ETA FORECAST SOUNDINGS DO NOT
SUPPORT HIGHS AS WARM AS NGM MOS EITHER. THINK THAT NGM MOS IS A
LITTLE TOO WARM CONSIDERING THE EXTENSIVE CLOUDS AND SCATTERED
PRECIP EXPECTED DURING THE AFTERNOONS.

IN THE EXTENDED FORECAST...LATEST MRF AND ECMWF STILL SUPPORT
PREVIOUS FORECAST (EXTENDED THROUGH FRIDAY). UPPER LOW WEAKENS
LEAVING A COL OVER THE MID MISSISSIPPI AND LOWER OHIO VALLEYS...WITH
STRONG SUBTROPICAL HIGHS TO THE EAST OVER THE ATLANTIC AND TO THE
WEST NEAR THE FOUR CORNERS AREA. WITHOUT ANY REAL CHANGE IN SURFACE
AIR MASS EXPECTED...WE WILL LIKELY SEE DIURNAL CONVECTION POP UP IN
THE WEAKNESS LEFT BETWEEN THE TWO UPPER HIGHS. WILL CONTINUE TO
CARRY A CHANCE OF SHOWERS/THUNDERSTORMS EACH DAY OF THE EXTENDED
FORECAST WITH SEASONAL TEMPERATURES.

.JKL...NONE.

HAL