Tornado and Flash Flooding in Indiana, September 20, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
309 AM EDT SUN SEP 20 2009

.SHORT TERM (TODAY AND TONIGHT)...

UPPER LEVEL TROUGH OVER THE PLAINS AND WEAK SFC WAVE OVER THE
MISSISSIPPI VALLEY NOSING INTO SOUTHERN ILLINOIS/WESTERN KENTUCKY
THIS MORNING. THESE FEATURES HAVE GENERATED SHOWERS AND SCT
T-STORMS OVER SOUTHWESTERN PARTS OF OUR AREA THIS MORNING. EXPECT
CONVECTIVE ACTIVITY TO EXPAND ACROSS THE AREA TOWARD SUNRISE AS A
STRONG H85 JET DEVELOPS ENHANCING CONVECTION.

ACCORDING TO THE 0Z NAM (PREFERRED MODEL)...WE SHOULD SEE A BREAK
IN PRECIP OR DECREASING COVERAGE EARLY THIS AFTERNOON. THEN
CONVECTION SHOULD REFIRE TONIGHT AS A VORT MAX ON THE SE SIDE OF
THE UPPER TROUGH STIRS THE ATMOSPHERE. SO SEVERAL CHANCES FOR
SHOWERS AND SCT T-STORMS IN THE SHORT RANGE. THE GREATEST THREATS
FROM THESE STORMS WILL BE HEAVY RAINFALL AND DANGEROUS LIGHTNING. IT
SHOULD BE NOTED THAT TIMING OF THE PRECIP WAVES STILL REMAINS A
BIT UNCERTAIN DUE TO POOR MODEL PERFORMANCE OVER THE LAST FEW
DAYS.

HIGH TEMPS THIS AFTERNOON WILL BE LIMITED TO THE MID TO UPPER 70S
THIS AFTERNOON. LWO TEMPS TONIGHT WILL BE QUITE MILD IN THE MID TO
UPPER 60S.

.LONG TERM (MONDAY THROUGH SATURDAY)...

WILL STAY THE COURSE THIS PERIOD WITH KEEPING SCT SHOWERS/TSTMS IN
THE FCST THRU THE WORKWEEK...FAVORING THE ECMWF/ENSEMBLES THOUGH THE
00Z RUN OF THE GFS IS A BIT WETTER THRU THU THAN THE PREVIOUS 3
RUNS. JUST A SUBTLE CHANGE WILL BE MADE MON NIGHT...TO LOWER
POPS...THIS FITS WELL WITH OUR NEIGHBORS.

IN THE UPR LEVELS...WE ARE IN MOIST SW FLO AT THE START OF THE
PERIOD WITH A CUTOFF LOW EVOLVING OVER THE WRN (CENTRAL) PLAINS LATE
MON/MON NIGHT. LOW WILL LIKELY MEANDER ACRS THE SRN/CENTRAL PLAINS
TUE THRU THU WITH RIPPLES ON THE EAST SIDE OF THE BROAD CYCLONIC
FLOW MOVING ACRS OUR REGION.

AT THE SFC...MOIST SLY FLOW IS PREVALENT THRU THE PERIOD AS ONE WAVE
PASSES TO OUR NORTH MON. A SLOW MOVG FRONTAL SYS APPROACHES
TUE...BEFORE STALLING ACRS FAR WEST KY AND WASHING OUT. IT APPEARS
THAT THE MOST WIDESPREAD ACTIVITY WILL BE EARLY MON IN STRONGEST SLY
FLOW AHEAD OF WEAKENING EWD MOVG TROF. MAY RAISE OUR CURRENT 50 POPS
TO LIKELY...THIS FAVORS THE GFS ENSEMBLES WHICH ARE A BIT HIGHER
THAN THE DETERMINISTIC GFS.

TEMPS WILL CONTINUE TO REFLECT MORE CLOUDS/SCT SHOWERS/STMS THRU THE
PERIOD...SIDING SEVERAL DEGS LOWER THAN GFS MOS.

&&

.AVIATION (20/06Z TAFS)...

LOTS OF VSBY/CIG RESTRICTIONS ANTICIPATED FOR THIS TAF
PERIOD...MOSTLY MVFR RESTRICTIONS BUT IFR CONDITIONS WILL BE
POSSIBLE AT TIMES ALSO.  AN UPPER LEVEL TROUGH AND ASSOCIATED WEAK
SFC LOW PRESSURE WAVE WILL BE RESPONSIBLE FOR PRECIP WAVES THIS
MORNING AND LATER TODAY.  HAVE RELIED ON THE 0Z NAM/18Z LOCAL WRF
FOR CONVECTION TIMING AS THESE MODELS SEEM TO HAVE THE BEST HANDLE
ON IT EARLY THIS MORNING.  THE FIRST MAIN WAVE OF PRECIP WILL BE IN
THE TIME PERIOD OF ABOUT 9Z TO 16Z FROM SOUTH TO NORTH ACROSS THE
TAF SITES.  EXPECT MODERATE TO HEAVY SHOWERS WITH ISLD T-STORMS
POSSIBLE ALSO.  IN THE STRONGEST STORMS...FLIGHT CONDITIONS WILL
DROP INTO THE IFR CATEGORY.  WE SHOULD SEE CONVECTION BECOME MORE
SCT IN NATURE BY THIS AFTERNOON...ALTHOUGH GUIDANCE STILL KEEPS MVFR
CIGS/VSBYS IN THE TAF SITES THROUGH THE AFTERNOON HOURS DUE TO
ABUNDANT LL MOISTURE.  THE NEXT ROUND OF HEAVIER MORE WIDESPREAD
PRECIP SHOULD ARRIVE LATE THIS AFTERNOON INTO THE EVENING HOURS.
ONCE AGAIN MVFR CONDITIONS ARE EXPECTED WITH IFR CONDITIONS
POSSIBLE.  IT SHOULD BE NOTED THAT MODEL PERFORMANCE WITH CONVECTION
OVER THE LAST 24 HRS HAS NOT BEEN THE GREATEST...SO CONFIDENCE IN
THE TIMING OF THE HEAVIER PRECIP WAVES FOR THIS TAF FORECAST IS
SOMEWHAT LOW TO AVERAGE.

WINDS SHOULD SHIFT FROM E TO SE THIS AFTERNOON POSSIBLY BECOMING
STRONGER THAN FORECAST IF SOME BREAKS IN THE CLOUDS OCCUR.

&&

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

SHORT TERM...AML
LONG TERM....DK
AVIATION.....AML

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE LOUISVILLE KY
430 AM EDT SUN SEP 20 2009

INZ076>079-083-084-089>092-KYZ023>043-045>049-053>057-061>067-
070>078-081-082-210830-
ORANGE IN-WASHINGTON IN-SCOTT IN-JEFFERSON IN-DUBOIS IN-
CRAWFORD IN-PERRY IN-HARRISON IN-FLOYD IN-CLARK IN-HANCOCK KY-
BRECKINRIDGE KY-MEADE KY-OHIO KY-GRAYSON KY-HARDIN KY-BULLITT KY-
JEFFERSON KY-OLDHAM KY-TRIMBLE KY-HENRY KY-SHELBY KY-FRANKLIN KY-
SCOTT KY-HARRISON KY-SPENCER KY-ANDERSON KY-WOODFORD KY-
FAYETTE KY-BOURBON KY-NICHOLAS KY-NELSON KY-WASHINGTON KY-
MERCER KY-JESSAMINE KY-CLARK KY-LARUE KY-MARION KY-BOYLE KY-
GARRARD KY-MADISON KY-BUTLER KY-EDMONSON KY-HART KY-GREEN KY-
TAYLOR KY-CASEY KY-LINCOLN KY-LOGAN KY-WARREN KY-SIMPSON KY-
ALLEN KY-BARREN KY-MONROE KY-METCALFE KY-ADAIR KY-RUSSELL KY-
CUMBERLAND KY-CLINTON KY-
430 AM EDT SUN SEP 20 2009 /330 AM CDT SUN SEP 20 2009/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTH CENTRAL
INDIANA AND CENTRAL KENTUCKY.

.DAY ONE...TODAY AND TONIGHT.

SHOWERS AND THUNDERSTORMS WILL CONTINUE TO MOVE NORTH OVER THE AREA
THROUGH MID MORNING. SOME OF THESE STORMS MAY PRODUCE AROUND 1 INCH
OF RAINFALL AND CLOUD TO GROUND LIGHTNING.

A DECLINE IN RAINFALL IS EXPECTED EARLY THIS AFTERNOON BEFORE
ANOTHER WAVE OF CONVECTION GETS GOING OVER OUR AREA TONIGHT. AGAIN
THE MAIN THREATS FROM ANY STORM WILL BE HEAVY RAINFALL AND DANGEROUS
LIGHTNING.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

SCATTERED THUNDERSTORMS ARE EXPECTED ACROSS THE OUTLOOK AREA THROUGH
THE PERIOD WITH THE MOST NUMEROUS STORMS EARLY MONDAY. AT THIS
TIME...SEVERE STORMS ARE NOT ANTICIPATED.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS ARE REQUESTED TO REPORT HEAVY RAINFALL TODAY.

AML/DK