Flash Flood Warning 276, NWS Memphis, TN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEMPHIS TN
846 PM CDT SAT AUG 21 2010

.UPDATE...
UPDATED TO CANCEL THE EXCESSIVE HEAT WARNING AND TO ADJUST POP/WX
GRIDS.

&&

.DISCUSSION...

A WEAKENING COLD FRONT ELONGATED FROM NEAR JONESBORO ARKANSAS...TO
UNION CITY TENNESSEE WILL CONTINUE TO SAG SOUTH THIS EVENING...AND
BE LOCATED SOUTH OF THE MEMPHIS METRO AREA BY 06Z. SCATTERED
CONVECTION AHEAD OF THE FRONT ALONG THE MISSISSIPPI/TENNESSEE
BORDER...ALONG WITH ISOLATED ACTIVITY ALONG THE BOUNDARY HAS
DROPPED TEMPERATURES DOWN BELOW THE EXCESSIVE HEAT WARNING
CRITERIA. THUS HAVE CANCELLED THE WARNING...REPLACING IT WITH THE HEAT
ADVISORY THAT RUNS THROUGH 9PM SUNDAY FOR THE MEMPHIS AREA AND
POINTS SOUTH. WILL ALLOW THE MIDNIGHT SHIFT TO TAKE A CLOSER LOOK
AT MODIFYING THE NORTHERN AREAS OF THE ADVISORY AS DEWPOINTS MAY
DRY OUT ENOUGH FURTHER SOUTH TOMORROW BEHIND THE FRONT.

CONVECTION IN THE SHORT TERM...HAVE INCREASED POPS OVER NORTHEAST
MISSISSIPPI THIS EVENING. AS STORMS WILL LIKELY CONTINUE TO DRIFT
SOUTHEAST OVER THE NEXT TWO HOURS. THIS LOCATION WILL ALSO BE THE
MOST FAVORABLE IN SEEING A STRONG OR ISOLATED SEVERE STORM AS THE
CONVECTION THIS EVENING HAS BEEN VERY PULSE NATURED AND UNDER THE
BEST UPPER LEVEL SUPPORT. LOWERED POPS SLIGHTLY FURTHER NORTH
WHERE NVA HAS BEGUN TO MOVE INTO THE REGION BEHIND THE FRONT. A
THREAT OF AN ISOLATED STORM STILL SEEMS REASONABLE AFTER MIDNIGHT
MAINLY ACROSS NORTHERN MISSISSIPPI.

JAB

&&

.PREV DISCUSSION... /ISSUED 628 PM CDT SAT AUG 21 2010/

UPDATE...
UPDATED TO ADD 00Z AVIATION DISCUSSION.

PREV DISCUSSION... /ISSUED 353 PM CDT SAT AUG 21 2010/

DISCUSSION...FORECAST FOCUS ON DANGEROUS HEAT HANGING ON ONE MORE
DAY...THEN COOLER AND MUCH LESS HUMID CONDITIONS THROUGH NEXT WEEK.

SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT.

DESPITE MLCAPE VALUES OF 2000-3000 J/KG THIS AFTERNOON...NOT MUCH
IN THE WAY OF THUNDERSTORMS HAVE DEVELOPED. HAVE A FEELING THIS IS
DUE TO THE OUTFLOW BOUNDARY THAT PUSHED THROUGH MUCH OF THE
MIDSOUTH DURING THE MORNING HOURS. THAT BOUNDARY HAS BEEN
PRODUCING SOME SMALL...WEAK THUNDERSTORMS ACROSS NORTHEAST
MISSISSIPPI BUT NOTHING OF SIGNIFICANCE. THE BEST FORCING HAS
SHIFTED TO THE NORTHEAST AND ALL THAT IS LEFT IS A DIFFUSE WIND
SHIFT LINE WHICH IS CONSIDERED THE 'COLD FRONT' FROM CENTRAL OK
THROUGH SOUTHERN MISSOURI AND SOUTHERN ILLINOIS. EVEN CU HAS BEEN
STRUGGLING TO DEVELOP...AND WHAT LITTLE HAS IS ACTUALLY STARTING
TO DISSIPATE AS DEW POINTS MIX OUT SOME. TO BE BLUNT...NOT
EXPECTING MUCH MORE TO DEVELOP EXCEPT ALONG AND SOUTH OF THIS
MORNING/S OUTFLOW BOUNDARY IN NORTHERN MISSISSIPPI FOR THE
REMAINDER OF THE DAY AND THROUGH TONIGHT. WILL STILL PLAY IT ON
THE SAFE SIDE AND INCLUDE A SLIGHT CHANCE FURTHER NORTH UP TO THE
I-40 CORRIDOR THIS EVENING FOR THAT STORM THAT COULD DEVELOP OUT
OF NOWHERE.

A HOT AND HUMID DAY HAS MATERIALIZED AS EXPECTED THOUGH WITH MUCH
MORE SUN THAN WHAT WAS ANTICIPATED EARLIER. MANY AREAS IN THE
CURRENT EXCESSIVE HEAT WARNING ARE APPROACHING OR HAVE ALREADY
EXCEEDED THE CRITERIA OF 110...SO THE WARNING WILL CONTINUE UNTIL
8 PM AS SCHEDULED.

THE FRONT WILL PASS THROUGH LATE TONIGHT AND RELIEF BEGINS SUNDAY
AFTERNOON ACROSS THE NORTHERN AREAS AS LOWER HUMIDITIES ARRIVE.
HIGH DEW POINTS WILL STILL EXIST NORTH OF THE FRONT A BIT SO
NRN MS/ECTRL AR AND FAR SRN TN WILL LIKELY HAVE HEAT INDEX VALUES
RANGING FROM 105 TO 109 AGAIN SUNDAY. WILL ISSUE A HEAT ADVISORY
FOR THESE AREAS FROM THIS EVENING THROUGH EARLY SUNDAY EVENING.
925 MB TEMPS WILL FALL SOMEWHAT SUNDAY...BUT WILL STILL RANGE FROM
+25 TO +27C THUS EXPECTING HIGHS IN THE MID 90S NORTH TO AROUND 100
SOUTH.

DRIER AIR BEGINS TO ARRIVE SUNDAY NIGHT WITH DEW POINTS IN THE
60S. CLEAR SKIES AND DRIER AIR WILL ALLOW TEMPS TO DROP INTO THE
60S NORTH AND LOW TO MID 70S SOUTH.

LONG TERM...MONDAY THROUGH NEXT SATURDAY.

A PERSISTENT NORTHEAST FLOW WITH DRY AIR ADVECTION WILL BE IN
PLACE FOR MUCH OF NEXT WEEK. ANOTHER FRONT WILL PASS THROUGH THE
AREA NEAR WEDNESDAY...BUT THE PRESENCE OF DRY AIR WILL MITIGATE
ANY CHANCE FOR PRECIP. CLEAR SKIES...VIRTUALLY ZERO CHANCE OF
RAIN...AND MUCH DRIER AIR WILL BE THE RULE FOR NEXT WEEK. ANOTHER
RIDGE MAY BUILD IN THE PLAINS NEXT WEEKEND AND SHOULD INCREASE
MOISTURE AND TEMPERATURES IN THE DAY 7-10 TIME FRAME.

BORGHOFF

&&

AVIATION...
00Z TAF CYCLE

VERY WEAK COLD FRONT STRETCHING FROM SOUTHERN ILLINOIS BACK
THROUGH SOUTHEAST MISSOURI AND WEST CENTRAL ARKANSAS WILL
MOVE INTO THE AREA TONIGHT. CONDITIONALLY UNSTABLE ATMOSPHERE IS
RECOVERING A BIT FROM EARLIER TODAY AS REFLECTED IN LATEST RADAR
TRENDS. AS A RESULT...ADDED CB INTO TAFS BETWEEN 22/00-02Z AND
WILL CONTINUE TO WATCH TRENDS FOR THE POSSIBILITY OF EXTENDING
CONVECTIVE CHANCES THROUGH AT LEAST 22/04Z. OTHERWISE...VFR
CONDITIONS EXPECTED FOR A MAJORITY OF THE TIME EXCEPT BETWEEN
22/08-12Z WHEN MVFR CONDITIONS WILL BE POSSIBLE MAINLY AT MKL/TUP.
SOUTHWEST/WEST WINDS TONIGHT WILL GRADUALLY WEAKEN TONIGHT AND
VEER NORTHEAST BY SUNDAY MORNING.

CJC

&&

.PRELIMINARY POINT TEMPS/POPS...
MEM  81 100  76  97 /  30  10   0   0
MKL  77  96  68  94 /  40   0   0   0
JBR  77  96  71  95 /  30   0   0   0
TUP  78 100  73  97 /  60  20   0   0

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...HEAT ADVISORY UNTIL 9 PM CDT SUNDAY FOR CRITTENDEN-CROSS-LEE AR-
     PHILLIPS-ST. FRANCIS.

MO...NONE.
MS...HEAT ADVISORY UNTIL 9 PM CDT SUNDAY FOR ALCORN-BENTON MS-CALHOUN-
     CHICKASAW-COAHOMA-DESOTO-ITAWAMBA-LAFAYETTE-LEE MS-MARSHALL-
     MONROE-PANOLA-PONTOTOC-PRENTISS-QUITMAN-TALLAHATCHIE-TATE-
     TIPPAH-TISHOMINGO-TUNICA-UNION-YALOBUSHA.

TN...HEAT ADVISORY UNTIL 9 PM CDT SUNDAY FOR FAYETTE-SHELBY.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE MEMPHIS TN
817 PM CDT SAT AUG 21 2010

ARZ008-009-017-018-026>028-035-036-048-049-058-MOZ113-115-
MSZ001>017-020>024-TNZ001>004-019>021-048>055-088>092-230330-
ALCORN-BENTON MS-CALHOUN-CARROLL-CHESTER-CHICKASAW-CLAY-COAHOMA-
CRAIGHEAD-CRITTENDEN-CROCKETT-CROSS-DESOTO-DECATUR-DUNKLIN-DYER-
FAYETTE-GIBSON-GREENE-HARDEMAN-HARDIN-HAYWOOD-HENDERSON-HENRY-
ITAWAMBA-LAFAYETTE-LAKE-LAUDERDALE-LAWRENCE-LEE AR-LEE MS-MADISON-
MARSHALL-MCNAIRY-MISSISSIPPI-MONROE-OBION-PANOLA-PEMISCOT-
PHILLIPS-POINSETT-PONTOTOC-PRENTISS-QUITMAN-RANDOLPH-SHELBY-
ST. FRANCIS-TALLAHATCHIE-TATE-TIPPAH-TIPTON-TISHOMINGO-TUNICA-
UNION-WEAKLEY-YALOBUSHA-
817 PM CDT SAT AUG 21 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EAST ARKANSAS...
THE MISSOURI BOOTHEEL...NORTH MISSISSIPPI...AND WEST TENNESSEE.

.DAY ONE...TONIGHT

A FEW STRONG OR SEVERE STORMS WILL BE POSSIBLE LATE THIS EVENING.
DAMAGING WINDS...LARGE HAIL...AND LOCALIZED FLASH FLOODING WILL BE
THE MAIN THREATS.

A HEAT ADVISORY IS IN EFFECT ALONG AND SOUTH OF A LINE FROM
CHERRY VALLEY ARKANSAS TO MEMPHIS TENNESSEE TO CORINTH
MISSISSIPPI. LOWS TONIGHT WILL LIKELY RANGE FROM THE UPPER 70S TO
LOWER 80S...OFFERING LITTLE RELIEF FROM THE HEAT FOR THOSE WITHOUT
AIR CONDITIONING.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

A HEAT ADVISORY WILL REMAIN IN EFFECT UNTIL 9 PM SUNDAY FOR AREAS
SOUTH OF A LINE FROM CHERRY VALLEY ARKANSAS TO MEMPHIS TENNESSEE
TO CORINTH MISSISSIPPI WHERE HEAT INDEX VALUES OF 105 TO 109
DEGREES ARE EXPECTED SUNDAY AFTERNOON.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED LATE THIS EVENING ACROSS THE
MIDSOUTH.

JAB

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