Severe Thunderstorm Warning 79, NWS Jackson, MS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
405 AM CST SAT MAR 30 2002

MAIN FORECAST CONCERNS INCLUDE FLOODING POTENTIAL NORTHERN AREAS...
AND SEVERE WEATHER POTENTIAL CNTRL/SRN PORTIONS OF AREA THROUGH
SUNDAY...

A VERY COMPLICATED SCENARIO IS UNDERWAY AS A STRONG UPPER LOW
PROGRESSES EASTWARD ACROSS TEXAS...PRECEDED BY MORE SUBTLE IMPULSES
ACROSS THE LOWER MS VALLEY REGION. THE SURFACE COLD FRONT IS
BEGINNING TO STALL OUT NEAR ELD TO CBM LINE. MODELS ARE IN GENERAL
AGREEMENT IN OPENING TX LOW UP AND SWEEPING IT EASTWARD ACROSS THE
FORECAST AREA SUNDAY. HOWEVER...CONSIDERABLE DIFFERENCES EXIST IN
MODEL DETAILS. MODELS HAVE BEEN TOO PROGRESSIVE WITH SOUTHWARD
MOVING COLD FRONT CONSIDERING LATEST TRENDS...AND HAVE TO NO
SURPRISE... UNDERESTIMATED STRONG MID LEVEL CAPPING
INVERSION...RESULTING IN A SOUTHWARD BIAS IN FORECASTED RAINFALL.
ETA QPF SOLUTION IS FAR REMOVED FROM REALITY AND WILL FOLLOW AVN
DETAILS DURING SHORT TERM OF FORECAST GIVEN BETTER CONSISTENCY AND
MORE REALISTIC QPF SOLUTION.

CONCERNING FLOODING POTENTIAL NORTHERN PORTIONS OF FORECAST
AREA...EXPECT STRONG ASCENT TO REDEVELOP LATER TODAY ALONG STEEPLY
SLOPED SFC-850MB FRONTAL BOUNDARY...WHERE PRECIPITABLE WATER AIRMASS
APPROACHING 1.75 INCHES WILL BE POOLING. MID LEVEL FORCING/COOLING
FROM APPROACHING MID LEVEL LOW WILL HELP INITIATE WIDESPREAD
CONVECTION. TSTMS WILL BE VERY EFFICIENT RAIN MAKERS AND PROSPECT
FOR CELL TRAINING HAS PROMPTED ISSUANCE OF FLASH FLOOD WATCH ALONG
AND NORTH OF BASTROP TO YAZOO CITY TO MACON LINE.

FARTHER SOUTH...GIVEN REALITY OF STRONGER MID LEVEL CAP AND FARTHER
NORTH FRONTAL BOUNDARY...WILL SIGNIFICANTLY REDUCE PRECIP CHANCES
FOR TODAY. HOWEVER...EXPECT CONDITIONS TO DETERIORATE OVERNIGHT AS
STRONG TO SEVERE CONVECTION DEVELOPS OVER ERN TX AND SWEEPS EASTWARD
INTO THE FORECAST AREA DURING PRE-DAWN HOURS. 06Z MESOETA INCREASES
MID LEVEL WIND FIELD SIGNIFICANTLY (70KTS AT 550MB) DURING THE
EVENING HOURS RESULTING IN RATHER IMPRESSIVE SHEAR PROFILES ACROSS
SRN AND CNTRL COUNTIES/PARISHES FOR TONIGHT. CONVECTIVE EVOLUTION IS
NOT CLEAR CUT AT THIS TIME...WITH TIMING OF ANY SOLID SQUALL LINE
DEVELOPMENT IN QUESTION. IF STORMS DEVELOP THIS EVENING IN WARM
SECTOR AHEAD OF COLD FRONT AND APPROACHING MID LEVEL LOW
OVER LA...IN THE IMPRESSIVE SHEAR ENVIRONMENT INDICATED BY
MODELS...THEY COULD QUICKLY BECOME SEVERE. THREAT FOR SEVERE
SUPERCELLS WILL LIKELY DECREASE LATE IN THE NIGHT AS MID LEVEL TROF
SHEARS A BIT RESULTING IN MORE UNIDIRECTIONAL FLOW. STILL...STRONG
SPEED SHEAR SHOULD SUPPORT AT LEAST A BROKEN SQUALL LINE...PROGGED
TO DEVELOP AND SWEEP ACROSS SRN/CNTRL PORTIONS OF FORECAST AREA
DURING MORNING HOURS SUNDAY...AND MOST LIKELY REDEVELOP SUN AFTN
OVER SE COUNTIES WHERE WARM SECTOR AIR SHOULD HAVE CHANCE TO
DESTABILIZE WITH AFTN HEATING. WILL MENTION SVR WORDING IN ZONES FOR
AREAS ALONG AND SOUTH OF PROGGED SURFACE BOUNDARY TONIGHT...AND OVER
PORTIONS OF CNTRL/SE MS FOR TOMORROW.

IN THE EXTENDED...WILL MAKE A FEW MINOR ADJUSTMENTS BASED ON LATEST
AVN GUIDANCE.

.JAN...
AR...FLASH FLOOD WATCH ASHLEY AND CHICOT COUNTIES.
LA...FLASH FLOOD WATCH MOREHOUSE...WEST CARROLL AND EAST CARROLL
PARISHES.
MS...FLASH FLOOD WATCH ALONG AND NORTH OF MAYERSVILLE TO YAZOO CITY
TO KOSCIUSKO TO MACON LINE.

43

ARZ074-075-LAZ007>009-015-016-023>026-MSZ018-019-025>066-072>074-
311200-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE JACKSON MS
0639 AM CST SAT MAR 30 2002

...THUNDERSTORMS...
SEVERE THUNDERSTORMS WILL BE POSSIBLE THIS AFTERNOON AND
TONIGHT...OVER EXTREME SOUTHEAST ARKANSAS...NORTHEAST LOUISIANA
AND PORTIONS OF CENTRAL MISSISSIPPI. THE HIGHEST THREAT FOR
SEVERE THUNDERSTORMS WILL EXIST ALONG AND SOUTH OF A LINE FROM
CROSSETT ARKANSAS TO GREENVILLE TO LEXINGTON MISSISSIPPI...AND
WEST OF A LINE FROM JACKSON TO NATCHEZ MISSISSIPPI. LOCATIONS
NORTH AND EAST OF THAT AREA WILL HAVE A CHANCE FOR ISOLATED
SEVERE THUNDERSTORMS. THE THREAT OF LARGE HAIL AND DAMAGING WIND
GUSTS WILL EXIST ACROSS ALL OF THE AREA THOUGHT TONIGHT. ANOTHER
THREAT WILL COME FROM THE POSSIBILITY OF TORNADOES. THE AREA WITH
THE HIGHEST CHANCE OF TORNADOES WILL EXIST ALONG AND SOUTH OF A
LINE FROM BASTROP LOUISIANA TO YAZOO CITY MISSISSIPPI AND WEST OF
A LINE FROM JACKSON TO NATCHEZ MISSISSIPPI.

A STRONG UPPER LEVEL STORM SYSTEM WILL MOVE EASTWARD OUT OF TEXAS
AND  PROVIDE STRONG VERTICAL MOTION. THIS LIFT...COMBINED WITH A
SURFACE LOW PRESSURE AREA AND VERY WARM UNSTABLE AIR...WILL SET
THE STAGE FOR STRONG AND SEVERE THUNDERSTORMS. THESE
THUNDERSTORMS WILL FIRST DEVELOP ALONG A PREEXISTING SURFACE
BOUNDARY IN CENTRAL MISSISSIPPI...THEN DEVELOP ALONG THE COLD
FRONT AS IT MOVES EASTWARD ACROSS THE LOWER MISSISSIPPI VALLEY
THIS AFTERNOON AND TONIGHT. THESE STORMS WILL CONTINUE INTO
EASTER SUNDAY MORNING BEFORE MOVING TO THE EAST SUNDAY AFTERNOON.

EVERYONE SHOULD STAY ABREAST OF FUTURE STATEMENTS AND FORECASTS
CONCERNING THIS EVOLVING SEVERE WEATHER EVENT.

ACTIVATION OF STORM SPOTTERS AND EMERGENCY MANAGEMENT PERSONNEL
WILL LIKELY BE REQUIRED THIS AFTERNOON AND TONIGHT.

...FLOODING...
THE EASTWARD MOVEMENT AND REBUILDING OF THE THUNDERSTORM
COMPLEXES WILL BRING THE POSSIBILITY OF HEAVY RAIN AND FLOODING.
LOCATIONS ALONG AND NORTH OF A LINE FROM BASTROP LOUISIANA TO
YAZOO CITY TO MACON MISSISSIPPI...WILL BE IN THE FAVORED AREA FOR
HEAVY RAIN. RAINFALL AMOUNTS OF 2 TO 5 INCHES WILL BE POSSIBLE IN
LOCALIZED AREAS.

FOR MORE INFORMATION PLEASE VISIT OUR WEBSITE AT
WWW.SRH.NOAA.GOV/JAN. THIS INCLUDES THE GRAPHICAL HAZARDOUS
WEATHER OUTLOOK.