Severe Thunderstorm Warning 200, NWS Louisville, KY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
435 PM EDT WED JUN 17 2009

.MESO UPDATE 1...

SVR TSTM WATCH 444 HAS JUST BEEN ISSUED THRU 02Z FOR WEST-CENTRAL KY
INCLUDING BWG...WEST OF EXISTING WATCH 439 VALID TIL 00Z. NEW WCN
HAS BEEN ISSUED DETAILING COUNTIES. SCT STG TO SVR CONVECTION HAS
BEEN ONGOING IN THE NEW WATCH AREA FOR LAST 1-2 HOURS. ADDITIONAL
CELLS ARE POSSIBLE IN THIS AREA LATE THIS AFTERNOON AND EARLY
EVENING. AN ENHANCED CU CLOUD FIELD EXISTS WEST OF CURRENT
CONVECTION IN CENTRAL KY INTO SRN IL. A FEW CELLS ARE STARTING TO
BREAK THE CAP OVER FAR SRN IL. ADDITIONAL CELLS COULD DEVELOP ALONG
THE WRN BOUNDARY AND PROPAGATE SEWD INTO PARTS OF WATCH 444.

FOR TSTMS ONGOING IN CENTRAL KY...THERE HAVE BEEN SEVERAL HAIL
REPORTS BUT ONLY ISOLATED WIND REPORTS SO FAR. GIVEN THE DEEP WARM
CLOUD DEPTH AVAILABLE TO THESE STORMS...TORRENTIAL RAIN AND PROLIFIC
CLOUD-TO-GROUND LIGHTNING HAVE BEEN OCCURRING WITH THE STRONGEST
CELLS. THE RAINFALL MAY CAUSE TEMPORARY FLOODING OF LOW SPOTS...
CREEKS...AND SOME ROADS.

UPDATED GRIDS AND ZFP WILL BE ISSUED SOON.

PREVIOUS DISCUSSION...
.SHORT TERM (TONIGHT AND THURSDAY)...

A SHORT WAVE MOVING THROUGH THE FLOW ACROSS THE UPPER OHIO VALLEY
THIS AFTERNOON HAS HELPED TO SET OFF THUNDERSTORMS ACROSS THE
FORECAST AREA WITH THE GREATEST CONCENTRATION ALONG A COUPLE OF
BOUNDARIES. ONE WAS LOCATED FROM SOUTHWEST INDIANA INTO EAST CENTRAL
KENTUCKY AND A SECOND FROM BUTLER COUNTY SOUTHEAST INTO CLINTON
COUNTY. THE STORMS HAVE DEVELOPED IN A VERY UNSTABLE ATMOSPHERE WITH
LIS FROM -5 TO -8. WE WILL HOLD ONTO THUNDERSTORMS THROUGH THE
EVENING BUT EXPECT THEM TO DISSIPATE TONIGHT AS THE S/W MOVES EAST
AND WE LOOSE THE DAY TIME HEATING.

WAS SURPRISED TO SEE NO FOG THIS MORNING WITH ABUNDANT MOISTURE AND
LIGHT WINDS SO WITH THE SAME CONDITIONS TONIGHT WE EXPECT FOG SHOULD
NOT BE MUCH OF A PROBLEM.

WITH A DEEPENING TROUGH OVER THE WEST THURSDAY RISING HEIGHTS WILL
BE NOTED OVER THE AREA. STILL THE SHORT RANGE MODELS INDICATE A WEAK
S/W MOVING OVER THE RIDGE THURSDAY AFTERNOON SO WILL WILL CONTINUE
TO MENTION STORMS TOMORROW WITH THE BEST CHANCE DURING THE AFTERNOON
OVER THE NORTH AND NORTHEAST PORTION OF THE FORECAST AREA.

TEMPERATURES THURSDAY WILL WARM INTO THE 90S THURSDAY AND WITH DEW
POINTS AROUND 70 DEGREES AFTERNOON HEAT INDICES WILL WARM INTO THE
MID AND UPPER 90S.

.LONG TERM (THURSDAY NIGHT THROUGH WEDNESDAY)...

THURSDAY NIGHT AND FRIDAY...

FOR THU EVENING...NW FLOW ALOFT WILL REMAIN OVER OUR AREA AND THERE
COULD BE RESIDUAL TSTMS OVER THE NRN AND ERN HALF OF FCST AREA NEAR
A RETREATING WARM FRONT. ANY TSTMS SHOULD MOVE TO OUR EAST
OVERNIGHT. THIS WILL SET THE STAGE FOR A HOT DAY FRI WITH HIGH TEMPS
IN THE LOWER AND MID 90S AND DEWPOINTS IN THE LOWER 70S. THIS WOULD
CREATE HEAT INDICES AROUND 100 FRI AFTERNOON...WHICH WOULD BE THE
HOTTEST DAY OF THE YEAR SO FAR.

AS FOR CONVECTION...AIR MASS WILL BE QUITE UNSTABLE DURING THE
AFTERNOON. HOWEVER...WITH UPPER FLOW BECOMING MORE WESTERLY...WARMER
AIR ALOFT WILL MOVE IN AS THE MAIN TSTM TRAJECTORY SHIFTS NWD. WITH
LITTLE APPARENT FORCING AT THIS TIME...IT APPEARS MOST OF FCST AREA
WILL REMAIN CAPPED ON FRI...EXCEPT POSSIBLY PARTS OF S-CNTRL IND IN
AFTERNOON WHERE ISOLD/SCT TSTMS WILL BE RETAINED IN THE FCST.

FRIDAY NIGHT AND SATURDAY...

MODELS HAVE BEEN IN DISAGREEMENT AS TO THE TIMING OF A SIGNIFICANT
SHORTWAVE WHICH IS PROGGED TO MOVE EWD FROM THE PLAINS STATES AND
BREAK DOWN THE UPPER RIDGE AS THE SHORTWAVE MOVES INTO THE GREAT
LAKES AND EVENTUALLY ERN U.S. OVER THE WEEKEND. ALL 12Z MODELS (GFS
NAM UKMET ECMWF AND CANADIAN) HAVE SLOWED THE SHORTWAVE AND THE
ASSOCIATED COLD FRONT MOVING SEWD ACROSS THE OH VALLEY. IF THIS
OCCURS...OUR AREA COULD STAY CAPPED/DRY LONGER THAN PREVIOUS FCST.

AS DISCUSSED IN SPCS DAY 3 CONVECTIVE OUTLOOK...THIS SYSTEM HAS THE
POTENTIAL TO CREATE AN ORGANIZED AND SVR LINEAR CONVECTIVE SYSTEM
(QLCS) THAT WOULD DRIVE E/SE ACROSS THE OHIO VALLEY FRI NIGHT.
HOWEVER... WITH MODELS SLOWING DOWN THEIR FORCING...WILL FOLLOW
CONSENSUS AND BACK OFF ON TIMING OF PRECIP FRI NIGHT OVER OUR FCST
AREA. HOWEVER WILL CONTINUE TO INDICATE A LINE OF TSTMS INFLUENCING
OUR AREA LATE FRI NIGHT/EARLY SAT...SINCE EVEN IF THE SYSTEM SLOWS
DOWN...IF A LINE OF CONVECTION IS TO OUR N...ITS COLD POOL COULD
ALLOW THE LINE TO MOVE SE FASTER THAN THE MEAN WIND AND FASTER THAN
WHAT THE MODELS MIGHT SUGGEST. THE TIMING OF THIS SYSTEM WILL NEED
TO BE WATCHED.

ON SATURDAY...WILL LINGER CHANCES FOR TSTMS OVER MOST OF THE
AREA...ESPECIALLY DOWNSTATE AS THE COLD FRONT SETTLES ACROSS THE
AREA. IF THE MODELS CONTINUE TO BE SLOWER WITH THIS SYSTEM...THEN
PROBABILITIES WILL NEED TO BE LOWERED FRI NIGHT AND RAISED ON
SAT.

SATURDAY NIGHT THROUGH WEDNESDAY...

MODELS ALSO HAVE BEEN INCONSISTENT IN DETERMINING HOW CNTRL U.S.
RIDGE AND ERN U.S. TROF PATTERN WILL EVOLVE DURING THE TIME PERIOD.
MODELS DO AGREE THAT A MORE AMPLIFIED UPPER AIR PATTERN WILL EMERGE
WITH GENERALLY A NORTHWEST TO NORTH MORE STABLE FLOW OVER THE OH
VALLEY. IF THE ERN TROF ENDS UP FARTHER E...THEN WARMER TEMPS WILL
OCCUR DURING THIS PERIOD. THE GFS HAS HAD A PROBLEM WITH ITS OWN
CONSISTENCY WHERE THE TROF WILL SET UP. THE ECMWF IS SIMILAR TO THE
GFS WHILE THE CANADIAN IS FARTHER WEST WITH THE UPPER TROF
SUGGESTING A BIT COOLER WEATHER OVER ERN FCST AREA. EITHER WAY...
GIVEN CURRENT MODEL SOLUTIONS...IT GENERALLY APPEARS TO BE A DRY
PERIOD SUN THROUGH WED.

&&

.AVIATION (12Z TAFS)...

A VERY UNSTABLE ATMOSPHERE WILL REMAIN IN PLACE ACROSS CENTRAL
KENTUCKY THIS AFTERNOON. SO WE EXPECT SCATTERED STORMS TO DEVELOP
WITH THE BEST CHANCE ACROSS THE SOUTH AND EAST. STILL WITH THE
UNCERTAINTY OF THE LOCATION OR TIME OF DEVELOPMENT WE WILL HOLD
ONTO VCTS IN THE TAFS. CLEARING SKIES AND LIGHT WINDS MAY ALLOW FOR
SOME PATCHY FOG AROUND DAYBREAK THURSDAY.

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

MESO UPDATE...TF
SHORT TERM....JA
LONG TERM.....TF
AVIATION......JA

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE LOUISVILLE KY
439 PM EDT WED JUN 17 2009

..TIME..    ...EVENT...     ...CITY LOCATION...      ...LAT.LON...
..DATE..    ....MAG....     ..COUNTY LOCATION.. ST.. ...SOURCE....
            ..REMARKS..

0438 PM     HAIL             ELIZABETHTOWN           37.70N  85.87W
06/17/2009  M0.88 INCH       HARDIN             KY   TRAINED SPOTTER

&&

EVENT NUMBER LMK0900055

SZAPPANOS