Severe Thunderstorm Warning 279, NWS Memphis, TN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEMPHIS TN
1007 AM CDT TUE MAY 27 2008

.UPDATE...

WILL MAKE MINOR ADJUSTMENTS TO THE FORECAST...MAINLY TO TWEAK RAIN
CHANCES...SKY COVER...AND TEMPERATURES.

&&

.DISCUSSION...

HEAVY RAINFALL AND FLASH FLOODING IS THE MAIN CONCERN TODAY
ACROSS THE MIDSOUTH...PARTICULARLY NEAR A DRESDEN TO LEXINGTON TO
SAVANNAH TN LINE. THE DEVELOPMENT OF STRONG TO SEVERE STORMS IS
THE NEXT CONCERN.

AT 10 AM CDT...VERY HEAVY RAINFALL WITH NUMEROUS SHOWERS
AND THUNDERSTORMS WERE OCCURRING NEAR THE LINE ABOVE.
ADDITIONAL SHOWERS AND THUNDERSTORMS WERE WEAKENING OVER ARKANSAS.
A WARM...MOIST...AND UNSTABLE AIRMASS WAS OVER THE MIDSOUTH WITH
TEMPERATURES MAINLY IN THE 70S UNDER MOSTLY CLOUDY SKIES. A WEAK
SURFACE TROUGH WAS DEVELOPING OVER THE MIDSOUTH...WHILE A MAIN
COLD FRONT WAS WELL NORTH OF THE AREA FROM CENTRAL MISSOURI TO
CENTRAL INDIANA.

HEAVY RAINFALL AND FLASH FLOODING ARE THE BIGGEST CONCERNS...
ESPECIALLY OVER PARTS OF WEST TN NEAR THE TN RIVER. LATEST RADARS
INDICATED THAT MANY AREAS EAST OF JACKSON TN...INCLUDING
LEXINGTON...PARSONS...AND SAVANNAH TN HAVE RECEIVED 2 TO 4
INCHES OF RAINFALL SINCE MIDNIGHT...WITH LOCALLY OVER 6 INCHES.
MANY FLOODED ROADS HAVE BEEN REPORTED IN DECATUR COUNTY. THIS AREA
OF RAIN WILL LIKELY CONTINUE THROUGH THE MORNING HOURS...BEFORE
PERHAPS DISSIPATING THIS AFTERNOON. MANY FLASH FLOODING WARNINGS
REMAIN IN EFFECT IN THESE AREAS AND ADDITONAL WARNINGS ARE LIKELY.

ACROSS THE REST OF THE MIDSOUTH...THINK SHOWERS AND THUNDERSTORMS
WILL HAVE NO PROBLEM DEVELOPING...PROBABLY BETWEEN 11 AM AND 3 PM
CDT ONCE TEMPERATURES REACH THE MID TO UPPER 80S. THESE SHOWERS
AND STORMS WILL BE SLOW MOVERS WITH WEAK WINDS ALOFT...LESS THAN
20 KTS 500 MB. WITH PRECIPITABLE WATER VALUES AROUND 1.8 INCHES...
HEAVY RAINFALL AND FLASH FLOODING REMAIN THE BIGGEST THREATS WITH
THE SHOWERS AND STORMS AS A QUICK 2 TO 4 INCHES OF RAINFALL COULD
OCCUR IN AN HOUR OR TWO. SINCE FLASH FLOODING IS ONGOING...WILL
NOT ISSUE A FLASH FLOOD WATCH...BUT WILL KEEP HEAVY RAINFALL
MENTION IN THE ZONES.

AS FAR AS THE SEVERE POTENTIAL IS CONCERNED...A FEW STORMS MAY BE
SEVERE WITH MODERATE TO HIGH INSTABILITY FORECAST...LIFTED INDICES
WILL BE -7 TO -9 WITH SBCAPES IN THE 3000 TO 4000 J/KG.
HOWEVER...WEAK WINDS SUPPORT PULSE STORMS AND SLOW MOVING
MULTICELL LINES/CLUSTERS. STILL...A FEW STORMS MAY BE SEVERE WITH
DAMAGING WINDS AROUND 60 MPH...BUT WIDESPREAD ORGANIZED SEVERE
STORMS APPEAR VERY UNLIKELY. LARGE HAIL IS VERY UNLIKELY WITH HIGH
FREEZING LEVELS AROUND 13500 FT MSL. OVERALL...THE POTENTIAL
FOR FLASH FLOODING AND HEAVY RAINFALL ARE GREATER THAN SEVERE
WEATHER...SO WILL REWORD THE HWO.

THINK TODAY/S RAIN CHANCES ARE IN GOOD SHAPE WITH THE HIGHEST
CHANCES OVER WEST TN NEAR THE TN RIVER WHERE RAIN IS ONGOING.
MOST AREAS WILL GET WET THIS AFTERNOON AND EVENING. THINK HIGH
TEMPERATURES WILL REACH THE 80S IN ALL LOCATIONS...AND PERHAPS 90
SOUTH OF INTERSTATE 40 AWAY FROM THE TN RIVER.

UPDATE WILL BE OUT SHORTLY.

&&

.PREV DISCUSSION... /ISSUED 425 AM CDT TUE MAY 27 2008/

DISCUSSION...SURFACE ANALYSIS THIS MORNING PLACES A QUASI-
STATIONARY BOUNDARY STRETCHING FROM THE EASTERN GREAT LAKES INTO
NORTHERN MISSOURI AND THEN BACK INTO THE CENTRAL PLAINS. REGIONAL
WSR-88D TRENDS SHOW A CLUSTER OF SHOWERS AND THUNDERSTORMS ACROSS
SOUTH CENTRAL ARKANSAS AND A DECAYING MCS STRETCHING FROM
SOUTHWEST MISSOURI INTO OKLAHOMA. TEMPERATURES RANGE FROM THE 60S
NORTH TO THE LOWER 70S SOUTH OF I-40. SEVERE WEATHER POTENTIAL
TODAY AND TONIGHT IS THE MAIN CONCERN IN THIS FORECAST PACKAGE.

TODAY THROUGH THURSDAY NIGHT...QUASI-STATIONARY BOUNDARY LOCATED
UPSTREAM WILL GRADUALLY MOVE SOUTH INTO THE LOWER MISSISSIPPI
VALLEY TONIGHT INTO WEDNESDAY. MEANWHILE...WEAKENING MCS
STRETCHING FROM SOUTHWEST MISSOURI BACK THROUGH WESTERN ARKANSAS
AND EASTERN OKLAHOMA WILL CONTINUE TO WEAKEN AS IT APPROACHES THE
MID SOUTH THIS MORNING. HOWEVER...AS INSTABILITY INCREASES WITH
DAYTIME HEATING ADDITIONAL SHOWERS AND THUNDERSTORMS ARE EXPECTED
TO DEVELOP. LEFT OVER OUTFLOW BOUNDARIES FROM YESTERDAY/S
CONVECTION WILL PROVIDE A LIFTING MECHANISM FOR ANY NEW
CONVECTION THAT DEVELOPS. MODEL SOUNDINGS/SHORT TERM CONVECTIVE
ANALYSIS YIELDS SURFACE BASED CAPE VALUES BETWEEN 2000-4000 J/KG
AND LIS BETWEEN -8 AND -9. IN ADDITION...FREEZING LEVELS ARE EXPECTED
TO BE AROUND 14KFT...WHICH WILL LIMIT OVERALL HAIL SIZE TODAY TO
AROUND THE SIZE OF NICKELS. NONETHELESS...DAMAGING WINDS IN EXCESS
OF 60 MPH AND LARGE HAIL WILL BE POSSIBLE WITH ANY THUNDERSTORMS
WHICH BECOME SEVERE. HEAVY RAINFALL IS ALSO POSSIBLE WITH THE
SHOWERS AND THUNDERSTORMS AS PRECIPITABLE WATER VALUES WILL BE
APPROACHING 2 INCHES.

SHOWERS AND THUNDERSTORMS ARE EXPECTED TO LINGER ACROSS THE MID
SOUTH WEDNESDAY AND WEDNESDAY NIGHT AS THE BOUNDARY SLOWLY DEPARTS
THE AREA BY THURSDAY MORNING AND HIGH PRESSURE RETURNS FOR
THURSDAY AFTERNOON INTO FRIDAY.

LONG RANGE...(FRIDAY THROUGH MONDAY)...00Z LONG RANGE MODELS
INDICATE VERY LITTLE CHANGE IN THE OVERALL UPPER AIR PATTERN
THROUGH MONDAY. THE LOWER MISSISSIPPI VALLEY WILL REMAIN ON THE
PERIPHERY OF THE UPPER LEVEL RIDGE WITH ANOTHER COLD FRONT MOVING
SOUTH INTO THE REGION FOR THE UPCOMING WEEKEND WILL NOT BUILD INTO THE
LOWER MISSISSIPPI VALLEY UNTIL THE MIDDLE OF NEXT WEEK. ANOTHER
COLD FRONT WILL MOVE SOUTH INTO THE REGION TOWARDS THE END OF THE
WEEKEND...PRODUCING ADDITIONAL CHANCES FOR SHOWERS AND
THUNDERSTORMS.

&&

.PRELIMINARY POINT TEMPS/POPS...
MEM  88  69  84  66 /  80  50  50  20
MKL  84  66  81  63 /  90  50  50  20
JBR  86  67  81  60 /  80  50  50  10
TUP  89  70  85  68 /  80  50  50  20

&&

.MEG WATCHES/WARNINGS/ADVISORIES...
AR...NONE.
MO...NONE.
MS...NONE.
TN...NONE.
&&

MBS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE MEMPHIS TN
1034 AM CDT TUE MAY 27 2008

ARZ008-009-017-018-026>028-035-036-048-049-058-MOZ113-115-
MSZ001>017-020>024-TNZ001>004-019>021-048>055-088>092-281745-
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-
1034 AM CDT TUE MAY 27 2008

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

.DAY ONE...TODAY AND TONIGHT

VERY HEAVY RAINFALL WILL CAUSE FLASH FLOODING IN SOME LOCATIONS
ACROSS THE MIDSOUTH TODAY AND TONIGHT...PARTICULARLY EAST OF
A DRESDEN TENNESSEE TO JACKSON TENNESSEE TO BURNSVILLE
MISSISSIPPI LINE. 2 TO 4 INCHES OF RAINFALL MAY OCCUR IN
SOME LOCATIONS IN 1 TO 2 HOURS.

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE ENTIRE
MIDSOUTH THROUGH 10 PM CDT. DAMAGING WINDS IN EXCESS OF 60 MPH AND
HAIL UP TO THE SIZE OF PENNIES ARE POSSIBLE WITH ANY THUNDERSTORMS
THAT BECOME SEVERE.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND TONIGHT.

MBS

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