Flash Flooding and Hail in Tennessee, April 20 to 21, 2006

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEMPHIS TN
307 AM CDT THU APR 20 2006

.DISCUSSION...

07Z SURFACE ANALYSIS PLACES THE QUASI STATIONARY FRONT ROUGHLY
ALONG INTERSTATE 40 THROUGH LITTLE ROCK AND THEN DOWN INTERSTATE
30 SOUTHWESTWARDS. A CLUSTER OF STORMS HAS DEVELOPED OVER CENTRAL
ARKANSAS JUST NORTH OF THIS FRONT. A SHORTWAVE WAS NOTED OVER THE
ARKLATEX REGION WHICH IS HELPING TO DRIVE CONVECTION AND GOOD
MOISTURE POOLING AT 850MB IS JUST OVER SOUTHERN ARKANSAS. MID
LEVEL LAPSE RATES OVER ARKANSAS...WEST TN AND MS THIS MORNING ARE
INCREDIBLY STEEP...NEARLY 8 C/KM. GOLF BALL SIZE HAIL HAD BEEN
REPORTED WITH THOSE STORMS WHICH IS NOT SURPRISING GIVEN THE
DEGREE OF INSTABILITY OVER THE REGION. NOT MUCH OF A TORNADO
THREAT WITH THE CONVECTION BEING MAINLY ELEVATED AND IN THE COOL
SECTOR. 850 MB MOISTURE IS NOT QUITE AS DEEP OVER THE FORECAST
AREA. HOWEVER EXPECT THAT AS THE SHORTWAVE APPROACHES THE REGION
FOR THE ENVIRONMENT EFFECTIVELY OVER ARKANSAS TO TRANSLATE
EASTWARD AND FOR ASSOCIATED CONVECTION TO MOVE INTO THE REGION
EARLY THIS MORNING. THE THREAT FOR SEVERE THUNDERSTORMS WILL
PERSIST A GOOD PART OF THE DAY WITH SEVERAL IMPULSES RIDING ALONG
THE BOUNDARY. MAIN THREAT WILL BE LARGE DAMAGING HAIL ALONG WITH
ISOLATED DOWNBURSTS. 0-6KM BULK SHEAR SUPPORTS ELEVATED SUPERCELLS
ALTHOUGH LOW LEVEL SHEAR BY ITSELF IS WEAK. AN ISOLATED TORNADO
CAN NOT BE ENTIRELY RULED OUT TODAY DUE TO THE INCREDIBLE AMOUNT
OF INSTABILITY AND OUTFLOW BOUNDARY INTERACTIONS POSSIBLY CREATING
ENOUGH LOCALIZED SHEAR. HOWEVER...A WIDESPREAD OUTBREAK IS NOT
EXPECTED. THE SLIGHT RISK AREA IS SOUTH OF A LINE FROM HARRISBURG
TO BLYTHEVILLE TO DYERSBURG TO PARIS. WOULD EXPECT THAT AS STORMS
TRY TO MOVE NORTHWARDS AWAY FROM THE FRONT THAT THEY WILL
WEAKEN. HOWEVER...WOULDNT BE SURPRISED IF A FEW STORMS NORTH OF
THIS LINE PRODUCE SEVERE HAIL EARLY THIS MORNING BASED UPON
CURRENT RADAR TRENDS. CLOUDS/RAIN WILL KEEP TEMPS COOLER FOR
TODAY...GUIDANCE GENERALLY ACCEPTED ON TEMPS.

CONVECTION SHOULD DIMINISH LATE THIS AFTERNOON AND FOR A TIME THIS
EVENING. HOWEVER ANOTHER MUCH STRONGER IMPULSE IS EXPECTED TO LIFT
OUT OF THE SOUTHWEST LATE TONIGHT AND DURING THE DAY ON FRIDAY.
VERY SIMILAR SETUP WITH STORMS AROUND MUCH OF THE DAY AS THIS
SYSTEM MOVES THROUGH. SEVERE WEATHER WILL BE MOST LIKELY NEAR AND
SOUTH OF STATIONARY FRONT WHICH IS GENERALLY EXPECTED TO REMAIN
ALONG THE I 40 CORRIDOR. HEAVY RAIN IS VERY POSSIBLE WITH THIS
NEXT IMPULSE WITH QPFS OF 1 TO 2 INCHES POSSIBLE. THIS COULD
RESULT IN LOCALIZED URBAN FLOODING DUE TO POOR DRAINAGE ALONG WITH
A FEW OF THE SMALLER STREAMS REACHING NEAR BANKFULL. INSTABILITY
NOT A PROBLEM AGAIN AND LOW LEVEL SHEAR REMAINS RELATIVELY WEAK.
SO LOOKING MAINLY AT A LARGE HAIL AND WIND THREAT. FAVOR MAV
GUIDANCE FOR HIGHS FRIDAY WHICH KEEPS HIGHS COOL DUE TO CLOUDS AND
RAIN THROUGH MUCH OF THE DAY.

SYSTEM SHOULD PULL AWAY FROM THE REGION FRIDAY NIGHT RESULTING IN
DRY CONDITIONS FOR SATURDAY. ANOTHER COLD FRONT WILL APPROACH THE
REGION SATURDAY NIGHT FROM THE NORTH. 00Z GFS SHOWS THIS FRONT
HANGING UP NORTH OF THE REGION WHICH SHOULD KEEP MUCH OF THE RAIN
AWAY UNTIL MONDAY NIGHT AND TUESDAY. AT THIS TIME A PROGRESSIVE
UPPER TROUGH SHOULD PUSH THE COLD FRONT THROUGH THE REGION.
PRELIMINARY GFS INSTABILITY PARAMETERS ARE FAVORABLE FOR MORE
SEVERE WEATHER WITH THIS NEXT FRONT.

&&

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

VALLE

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE MEMPHIS TN
343 AM CDT THU APR 20 2006

ARZ008-009-017-018-026>028-035-036-048-049-058-MOZ113-115-
MSZ001>017-020>024-TNZ001>004-019>021-048>055-088>092-211045-
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-
343 AM CDT THU APR 20 2006

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

.DAY ONE...TODAY AND TONIGHT

THERE IS A SLIGHT RISK FOR SEVERE THUNDERSTORMS TODAY ALONG AND SOUTH
OF A LINE FROM JONESBORO TO BLYTHEVILLE TO DYERSBURG TO PARIS. A
STATIONARY FRONT WILL BE LOCATED ROUGHLY ALONG INTERSTATE 40
TODAY. CLUSTERS OF THUNDERSTORMS ARE EXPECTED TO RIDE ALONG THE
FRONT THROUGH MUCH OF THE DAY. LARGE DAMAGING HAIL ALONG WITH
LOCALLY DAMAGING WINDS ARE POSSIBLE. THUNDERSTORMS SHOULD DIMINISH
THIS EVENING HOWEVER ANOTHER ROUND OF THUNDERSTORMS IS EXPECTED TO
REDEVELOP OVER EAST TEXAS AND SURGE NORTHEASTWARD OVERNIGHT. SOME
OF THESE STORMS COULD BE SEVERE WITH LARGE HAIL AND LOCALLY
DAMAGING WINDS.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

ANOTHER ROUND OF THUNDERSTORMS IS EXPECTED TO ARRIVE VERY EARLY
FRIDAY MORNING AND PERSIST THROUGH MUCH OF THE DAY. A SLIGHT RISK
OF SEVERE THUNDERSTORMS EXISTS ALONG AND SOUTH OF INTERSTATE 40.
THE MAIN THREATS INCLUDE LARGE DAMAGING HAIL...DAMAGING WINDS AND
LOCALIZED FLOODING.

ANOTHER COLD FRONT IS EXPECTED TO ARRIVE ON TUESDAY. SEVERE
THUNDERSTORMS WILL BE POSSIBLE WITH THIS FRONT.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED TODAY...LATE TONIGHT AND ON
FRIDAY. ACTIVATION MAY ALSO BE NEEDED ON TUESDAY.

VALLE

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE MEMPHIS TN
347 AM CDT THU APR 20 2006

ARZ017-200915-
LAWRENCE AR-
347 AM CDT THU APR 20 2006

THIS SIGNIFICANT WEATHER ADVISORY IS FOR...LAWRENCE COUNTY.

A STRONG THUNDERSTORM CAPABLE OF PRODUCING PEA TO DIME SIZE HAIL WAS
LOCATED 6 MILES SOUTHWEST OF MINTURN AT 347 AM CDT...MOVING NORTHEAST
AT 30 MPH.

PEOPLE IN LAWRENCE COUNTY...INCLUDING THE CITIES OF HOXIE AND WALNUT
RIDGE...SHOULD MONITOR THIS STORM CLOSELY.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE MEMPHIS TN
515 AM CDT THU APR 20 2006

ARZ028-MOZ113-115-201045-
MISSISSIPPI AR-DUNKLIN MO-PEMISCOT MO-
515 AM CDT THU APR 20 2006

THIS SIGNIFICANT WEATHER ADVISORY IS FOR...DUNKLIN...MISSISSIPPI AND
PEMISCOT COUNTIES.

A STRONG THUNDERSTORM CAPABLE OF PRODUCING PEA TO DIME SIZE HAIL WAS
LOCATED 4 MILES WEST OF GOSNELL AT 515 AM CDT...MOVING EAST AT 40
MPH.

PEOPLE IN DUNKLIN...MISSISSIPPI AND PEMISCOT COUNTIES...INCLUDING THE
CITIES OF BLYTHEVILLE...GOSNELL AND STEELE...SHOULD MONITOR THIS
STORM CLOSELY.