Severe Thunderstorm Warning 28, NWS Louisville, KY

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOUISVILLE KY
548 PM EDT SAT APR 24 2010

...MESOSCALE UPDATE...

SEVERE SQUALL LINE HAS DEVELOPED FROM HAWESVILLE KY TO EAST OF
MEMPHIS. THIS SQUALL LINE WILL CONTINUE TO PLOW TO THE NORTHEAST AND
SHOULD MAINTAIN ITS INTENSITY THROUGH AT LEAST 00Z. DESPITE THE
FORMATION OF A LINE...WE MUST NOT RULE OUT THE CONTINUING
POSSIBILITY OF TORNADOES. INDEED...SEVERAL STRONGLY ROTATING STORMS
HAVE ALREADY BEEN NOTED ALONG THE LEADING EDGE OF THE LINE.

THE ATMOSPHERE IS MOST UNSTABLE IN THE BOWLING GREEN AREA. WHILE
INSTABILITY IN CENTRAL KENTUCKY IS NOT NEARLY AS ROBUST AS TO THE
SOUTHWEST...SHEAR IS STILL VERY STRONG AS SEEN ON LVX VWP. ALL
INTERESTS IN CENTRAL KENTUCKY MUST CONTINUE TO BE ON GUARD FOR
POSSIBLE ADDITIONAL TORNADOES EARLY THIS EVENING.

SEVERE THREAT WILL SHIFT EASTWARD THIS EVENING AS LOW LEVEL JET
INCREASES TO 60KT AND PROGRESSES TO THE EAST OVER CENTRAL KENTUCKY.
SHEAR WILL REMAIN HIGH AS WELL. INSTABILITY WILL DECREASE AFTER
00Z...BUT ROTATING STORMS WILL STILL BE POSSIBLE ACROSS CENTRAL
KENTUCKY AND FAR SOUTHERN INDIANA.

THE SEVERE THREAT SHOULD END FROM WEST TO EAST BETWEEN 03Z AND 06Z.

.SHORT TERM (TONIGHT AND SUNDAY)...

FOCUS CONTINUES ON SEVERE WEATHER THREAT. EXPECT MULTIPLE MESOSCALE
DISCUSSIONS TO COME UP FOR THE REST OF THE AFTERNOON AND EVENING.
EXPECT THE SEVERE THREAT TO END BY MID EVENING...BUT SHOWER CHANCES
WILL CONTINUE OVERNIGHT AS MID LEVEL DRY AIR WILL LIMIT DEEP
CONVECTION. BY SUNDAY...FRONT WILL NOT COME THROUGH UNTIL LATER
SUNDAY. SO COULD SEE SOME LOW TOPPED CONVECTION DEVELOP WITH STEEP
LOW LEVEL LAPSE RATES. HAVE WORDING FOR STORMS IN THE AFTERNOON IN
THE GRIDS.

.LONG TERM (SUNDAY NIGHT - SATURDAY)...

JUST A BROAD-BRUSH DISCUSSION FOR THE EXTENDED THIS ISSUANCE DUE TO
SIGNIFICANCE OF INCOMING SEVERE THREAT.

LARGE VERTICALLY STACKED LOW OVER INDIANA AT THE START OF THE PERIOD
WILL DRIFT EAST TOWARD THE ATLANTIC COAST BY 00Z TUESDAY.  BROAD
UPPER TROF ASSOCIATED WITH SURFACE LOW MAINTAINS AXIS OVER EASTERN
U.S. THROUGH WEDNESDAY...KEEPING COOLER NORTHERLY FLOW FOR THE
AREA...RESULTING IN TEMPS AT OR BELOW NORMS FOR THE FIRST HALF OF
THE WEEK.  BY THURSDAY...UPPER RIDGE MOVES INTO THE OHIO VALLEY
ALLOWING FOR RETURN OF SOUTHERLY FLOW AND TEMPS WARMING BACK INTO
THE 70S FOR HIGHS AND 50S FOR LOWS....UP FROM 40-MID 60 RANGE FOR
MIN/MAX RANGE IN THE FIRST HALF OF WEEK.

ANOTHER BROAD UPPER TROF DEVELOPS OVER THE WESTERN U.S. BY
FRIDAY...WITH THE CAHNCE FOR THUNDERSTORMS RETURNING FOR NEXT
WEEKEND.

BY EARLY SUNDAY...THE STRONG STORM SYSTEM RESPONSIBLE FOR SATURDAY'S
STORMS WILL MORPH INTO A VERTICALLY STACKED...FILLING...OCCLUDED
CYCLONE JUST SOUTH OF CHICAGO. ALTHOUGH BEGINNING TO WEAKEN...THE
PRESSURE ASSOCIATED WITH THE SURFACE LOW IS STILL FORECAST TO BE A
QUITE DEEP 885MB OR SO. DRY MID LEVEL AIR WILL HAVE OVERSPREAD THE
COMMONWEALTH DURING THE PREDAWN HOURS IN THE WAKE OF A COLD FRONT.
HOWEVER...SEASONABLY COLD AIR WILL STILL LIE WELL NORTH OF THE OHIO
RIVER THROUGH MID AFTERNOON SUNDAY. THIS COOLER AIR WILL SAG
SOUTHWARD BEHIND A SECONDARY COLD FRONT ASSOCIATED WITH THE ARRIVAL
OF THE BY NOW ELONGATED 500MB TROUGH.

AFTER A PARTLY CLOUDY...BREEZY BUT STILL MILD SUNDAY
MORNING...STEEPENING LAPSE RATES COUPLED WITH HEIGHT FALLS
ASSOCIATED WITH THE APPROACHING 500MB TROUGH WILL LIKELY SPARK
SCATTERED FAST MOVING LOW-TOPPED SHOWERS AND THUNDERSTORMS DURING
THE AFTERNOON AND EVENING HOURS. THESE STORMS WILL HAVE TO POTENTIAL
TO BRING GUSTY WINDS AND PERHAPS SOME SMALL HAIL. INITIALLY...THE
BEST COVERAGE WILL LIE ACROSS SOUTHERN INDIANA. BY EVENING...THIS
CONVECTION WILL SAG SOUTH TOWARDS CENTRAL KENTUCKY.

WILL CONTINUE A CHANCE FOR SHOWERS SUNDAY NIGHT ACROSS THE ENTIRE
AREA AS THE 500MB TROUGH AXIS MOVES OVERHEAD. COLDER AIR WILL ARRIVE
AND WILL KEEP MONDAY QUITE CLOUDY WITH AFTERNOON HIGHS STRUGGLING TO
EXCEED 60 ALONG AND NORTH OF INTERSTATE 64.

LATE MONDAY AS A LONGWAVE TROUGH DEVELOPS ACROSS NEW ENGLAND...AS
SECONDARY 500MB TROUGH WILL SLIDE SOUTHEAST TOWARDS THE LOWER OHIO
VALLEY. THIS WILL CROSS THE AREA TUESDAY AFTERNOON AND WILL LIKELY
BRING A SECOND CLOUDY COOL DAY WITH A CHANCE OF SOME LIGHT SHOWERS.

.WEDNESDAY THROUGH FRIDAY...

A SUBSTANTIAL WARMING TREND WILL BEGIN WEDNESDAY THAT WILL LIKELY
BRING HIGH TEMPERATURES WELL BACK UP INTO THE MID TO UPPER 70S
THURSDAY THROUGH SATURDAY. THE UPPER AIR PATTERN WILL AMPLIFY
WEDNESDAY AS THE FIRST OF A SERIES OF STRONG STORMS MOVE ACROSS THE
PACIFIC NORTHWEST. EVENTUALLY...A TROUGH WILL DEVELOP ACROSS THE
ROCKIES BY THE EARLY PART OF NEXT WEEKEND. CORRESPONDING...RIDGING
ACROSS THE WESTERN PLAINS WILL GRADUALLY TRANSLATE EAST AND BRING
RISING HEIGHTS ACROSS THE LOWER OHIO VALLEY. AT THE SURFACE...HIGH
PRESSURE WILL MOVE ACROSS THE COMMONWEALTH WEDNESDAY AND BECOME
ESTABLISHED ACROSS THE SOUTHEASTERN STATES BY LATE FRIDAY.

EXPECT MOSTLY SUNNY SKIES AND LIGHT WINDS WEDNESDAY. SOUTHERLY FLOW
WILL BEGIN THURSDAY...BRINGING PARTLY CLOUDY SKIES AND THE START OF
A NICE WARMUP.

&&

.AVIATION (18Z TAF ISSUANCE)...

WIDESPREAD SHOWER AND THUNDERSTORM ACTIVITY EXPECTED INTO THE EARLY
EVENING HOURS AT THE TAF SITES. GIVEN HIGH POTENTIAL FOR SEVERE
WEATHER...NOT EXPECTING THE BEST FLYING CONDITIONS DURING THIS
PERIOD. FOR NOW HAVE MVFR TO IFR CONDITIONS IN THE TAFS AS WELL AS
30-35 KNOT WINDS...THOUGH WINDS CERTAINLY COULD BE STRONGER. EXPECT
SEVERE ACTIVITY TO WIND DOWN BY MID EVENING...BUT SHOWERS ARE
POSSIBLE AS THE DRIVING LOW WILL STALL OVER ILLINOIS. COULD BE
ANOTHER ROUND OF STORMS SUNDAY LATE MORNING AND AFTERNOON.

&&

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

MESOSCALE......13
SHORT TERM.....RJS
LONG TERM......JBS
AVIATION.......RJS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE LOUISVILLE KY
315 PM EDT SAT APR 24 2010

INZ076>079-083-084-089>092-KYZ023>043-045>049-053>057-061>067-
070>078-081-082-250400-
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-
315 PM EDT SAT APR 24 2010 /215 PM CDT SAT APR 24 2010/

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

.DAY ONE...TONIGHT.

SHOWERS AND STORMS ARE EXPECTED TO CONTINUE ACROSS THE REGION THIS
EVENING. THESE STORMS ARE IN ASSOCIATION WITH A DEVELOPING
VIGOROUS LOW PRESSURE SYSTEM EXPECTED TO MOVE NORTH ACROSS THE
MISSISSIPPI RIVER VALLEY. MULTIPLE LINES OF STORMS ARE EXPECTED TO
BRING THE POTENTIAL FOR DAMAGING WINDS AS WELL AS STRONG
TORNADOES...LARGE HAIL...AND FREQUENT CLOUD TO GROUND LIGHTNING.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY.

A COLD FRONT WILL SAG SOUTH ACROSS THE OHIO RIVER DURING THE LATE
AFTERNOON HOURS ON SUNDAY. SCATTERED THUNDERSTORMS OVER SOUTHERN
INDIANA DURING THE AFTERNOON WILL MOVE SOUTHEAST ACROSS NORTH
CENTRAL KENTUCKY BE EARLY EVENING. THESE SHOWERS AND STORMS MAY
BRING GUSTY WINDS AND SMALL HAIL TO LOCATIONS UNDER SOME OF THE
STRONGEST CELLS.

ANOTHER COLD FRONT WILL APPROACH THE REGION FRIDAY...BRINGING A
SLIGHT CHANCE FOR THUNDERSTORMS.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS SHOULD MONITOR THE WEATHER SITUATION THIS EVENING AND CALL
IN REPORTS AS NECESSARY.

RJS/JBS

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