Severe Thunderstorm Warning 20, NWS Louisville, KY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
719 PM EDT WED APR 7 2010

...UPDATED AVIATION DISCUSSION...

.SHORT TERM (TONIGHT AND THURSDAY)...

MODELS AND WATER VAPOR SHOW A DEEP PROGRESSIVE 500MB TROUGH
CURRENTLY MOVING ACROSS THE SOUTHERN PLAINS. THIS FEATURE IS
FORECAST TO STEADILY MOVE EAST WITH ITS BASE CROSSING THE
COMMONWEALTH LATE THURSDAY. LOW PRESSURE NOW OVER CENTRAL ILLINOIS
IS FORECAST TO DEEPEN SLIGHTLY AND MOVE OVER THE DETROIT AREA BY
THURSDAY MORNING. A SEASONALLY STRONG COLD FRONT WILL MOVE SOUTHEAST
OF THE OHIO RIVER DURING THE PRE-DAWN HOURS TOMORROW.

A LINE OF CONVECTION IS CURRENTLY BEGINING TO FORM JUST EAST OF A
PSEUDO-DRY LINE/COLD FRONT ACROSS CENTRAL MISSOURI. THIS LINE IS
EXPECTED TO INTENSIFY AND MOVE INTO OUR NORTHWESTERN COUNTIES AROUND
00Z THIS EVENING...THEN CROSS OVER OUR FORECAST AREA OVERNIGHT AND
THEN EXIT THE BLUEGRASS AND LAKE CUMBERLAND REGIONS THURSDAY
MORNING. ALTHOUGH THE BULK OF OUR PRECIPITATION WILL FALL
OVERNIGHT...SOME SPRINKLES OR SCATTERED LIGHT SHOWERS WILL LIKELY
MOVE INTO OUR WESTERN COUNTIES BY MID TO LATE AFTERNOON.

CURRENT CLOUD COVER AND ONLY MARGINALLY STEEP LAPSE RATES WILL LIMIT
THE INTENSITY OF THIS EXPECTED LINE OF CONVECTION AS IT APPROACHES
LATE THIS EVENING. HOWEVER...INCREASING MOISTURE AND THE RELATIVELY SLOW
MOVEMENT OF THE COLD FRONT WILL BRING SEVERAL HOURS OF MODERATE TO
BRIEFLY HEAVY RAINFALL OVERNIGHT...WITH WIDESPREAD RAINFALL AMOUNTS
OF AROUND ONE INCH EXPECTED. DESPITE THE WEAK INSTABILITY...ANY
STORMS THAT CAN MIX DOWN STRONGER WINDS ALOFT MAY PRODUCE ISOLATED
SEVERE WIND GUSTS.

SHOWERS WILL BE ENDING ACROSS OUR EASTERN COUNTIES AROUND DURING THE
MORNING HOURS. FEEL THAT ANY BRIEF SUNNY INTERVALS THAT DEVELOP
TOMORROW MORNING WILL QUICKLY BE REPLACED BY WIDESPREAD STRATO-CU AS
LOW LEVEL MOISTURE WRAPPING AROUND THE WESTERN SIDE OF THIS GREAT
LAKES STORM ENCOUNTERS STEEPENING LOW LEVEL LAPSE RATES.

INCREASING WINDS FROM THE WEST TOMORROW AFTERNOON COMBINED WITH
EXPECTED HIGHS ONLY IN THE UPPER 50S WILL MAKE IT FEEL PRETTY RAW
AND BLUSTERY.

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

BY THURSDAY EVENING THE UPPER LEVEL TROUGH AXIS WILL BE POSITIONED
TO THE EAST OF THE FORECAST AREA WITH HIGH PRESSURE AT THE SURFACE
RIDGING IN FROM THE SOUTHWEST. DEEP NORTHWESTERLY FLOW WILL BE
PRESENT USHERING IN MUCH COLDER AND DRIER AIR THAN WE HAVE SEEN
RECENTLY. LOWS SHOULD DROP INTO THE UPPER 30S ON FRIDAY MORNING WITH
SKIES GRADUALLY CLEARING OVERNIGHT. FRIDAY LOOKS TO BE A COOL AND
SOMEWHAT WINDY DAY. NORTHWEST WINDS WILL CONTINUE WITH HIGHS
STRUGGLING TO REACH 60 FOR A SECOND DAY IN A ROW.

BY FRIDAY NIGHT UPPER LEVEL FLOW TRANSITIONS TO MORE ZONAL WITH HIGH
PRESSURE DIRECTLY OVER THE REGION. MOSTLY CLEAR SKIES AND CALM WINDS
WILL ALLOW FOR GOOD RADIATIONAL COOLING FRIDAY NIGHT INTO SATURDAY
MORNING. WITH THIS TEMPERATURES WILL DROP TO NEAR THE DEWPOINTS IN
THE MID TO LOWER 30S. IT LOOKS LIKE SOME PATCHY FROST WILL BE A
DISTINCT POSSIBILITY ESPECIALLY OVER EAST CENTRAL KENTUCKY. THIS
COULD POTENTIALLY CAUSE SOME DAMAGE TO EARLY BLOOMING VEGETATION.

BY SATURDAY EVENING THE BUBBLE OF HIGH PRESSURE WILL MOVE EAST OF
THE AREA AND RIDGING BUILDING IN ALOFT. THIS WILL ALLOW WINDS TO
SHIFT TO A MORE SOUTHERLY DIRECTION. HIGH PRESSURE AND RIDGING ALOFT
WILL REMAIN IN CONTROL OF OUR WEATHER THROUGH THE END OF THE LONG
TERM. THIS WILL KEEP THE REGION DRY UNDER PARTLY TO MOSTLY SUNNY
SKIES THROUGH WEDNESDAY. A GRADUAL WARM-UP WILL CONTINUE THROUGH
MIDWEEK WITH HIGHS SUNDAY THROUGH WEDNESDAY RANGING FROM THE LOWER
TO MID 70S...WELL ABOVE NORMAL. LOW TEMPERATURES WILL BE IN THE
UPPER 40S TO LOWER 50S.

&&

.AVIATION (00Z TAF ISSUANCE)...

A LINE OF THUNDERSTORMS JUST WEST OF CENTRAL KENTUCKY WILL
OVERSPREAD THE REGION TONIGHT. WE HAVE THUNDERSTORMS IN BWG BY
02Z... SDF BY 01Z... AND LEX BY 03Z. THESE TIME MAY BE A LITTLE FAST
BUT NOT BY MUCH. THE STORMS ARE ALONG AND AHEAD OF AN APPROACHING
COLD FRONT. POST FRONTAL WINDS WILL SHIFT TO THE NORTHWEST WITH
GUSTS TO 20 MPH. WE ALSO EXPECT CIGS TO LOWER INTO THE MVFR CATEGORY
WITH SCATTERED SHOWERS CONTINUING INTO MID DAY THURSDAY.

&&

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

SHORT TERM........JSD
LONG TERM.........EES
AVIATION..........JA

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE LOUISVILLE KY
339 PM EDT WED APR 7 2010

INZ076>079-083-084-089>092-KYZ023>043-045>049-053>057-061>067-
070>078-081-082-081945-
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-
339 PM EDT WED APR 7 2010 /239 PM CDT WED APR 7 2010/

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

.DAY ONE...THIS AFTERNOON AND TONIGHT.

A COLD FRONT WILL APPROACH THE AREA TONIGHT BRINGING A LINE OF
THUNDERSTORMS TO THE AREA MAINLY THIS EVENING BETWEEN 9 PM EDT AND
4 AM EDT. INSTABILITY WILL BE LIMITED...HOWEVER SOME OF THE
STRONGER STORMS MAY CONTAIN ISOLATED DAMAGING WIND GUSTS. ANY
THUNDERSTORMS MAY CONTAIN BRIEF HEAVY RAIN AND LIGHTNING.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.

A COOL AND DRY AIRMASS WILL MOVE INTO THE REGION FRIDAY NIGHT AS
HIGH PRESSURE DOMINATES THE AREA. THE COMBINATION OF LOW DEW
POINTS...LIGHT WINDS...AND CLEAR SKIES WILL LEAD TO THE POTENTIAL
FOR A FROST BY DAWN ON SATURDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED AT THIS TIME.

JSD