Severe Thunderstorm Warning 518, NWS Jackson, MS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
420 AM CST THU DEC 19 2002

MAIN FORECAST CHALLENGE IS THE SEVERE WEATHER EVENT EXPECTED TODAY
OVER THE ENTIRE FORECAST AREA.

AN UNSEASONABLY WARM AND HUMID ATMOSPHERE IS IN PLACE OVER THE
ENTIRE FORECAST AREA TODAY...SETTING THE STAGE FOR A MAJOR SEVERE
WEATHER EVENT AS MANY PARAMETERS ARE COMING TOGETHER FOR A SLOW
MOVING PROGRESSION OF THUNDERSTORMS...SOME SEVERE ACROSS THE FORECAST
AREA DURING THE DAY TODAY. SOME SHOWERS AND THUNDERSTORMS MAY
PERSIST INTO THE EVENING HOURS...ESPECIALLY IN EASTERN
SECTIONS...BUT EXPECT THE MAIN SEVERE ACTIVITY TO BE DURING THE DAY
ON THURSDAY.

A LINE OF STRONG TO SEVERE THUNDERSTORMS IS ONGOING AT THIS TIME
ALONG THE NORTHWEST PORTION OF OUR FORECAST AREA. AT AROUND
4 AM...THE LINE STRETCHED FROM NORTHERN SUNFLOWER COUNTY
MISSISSIPPI SOUTHEASTWARD INTO ASHLEY COUNTY ARKANSAS. ISOLATED
SHOWERS WERE OCCURRING EAST OF THE MAIN LINE OF STORMS AS FAR EAST
AS THE JACKSON METRO AREA. A TORNADO WATCH IS IN EFFECT UNTIL 10 AM
AND AFFECTS PORTIONS OF OUR FORECAST AREA FROM WEBSTER COUNTY
SOUTHEASTWARD THROUGH YAZOO AND WARREN COUNTIES AND DOWN TO ADAMS
COUNTY. ALL OF OUR LOUISIANA PARISHES AND BOTH OF OUR ARKANSAS
COUNTIES ARE AFFECTED BY THE CURRENT WATCH.

A STRONG UPPER LEVEL TROUGH IS EXPECTED TO MOVE SOUTHEASTWARD ACROSS
TEXAS TODAY. AHEAD OF THIS TROUGH...A SURFACE LOW AND TRAILING COLD
FRONT WILL MOVE SLOWLY ACROSS MISSISSIPPI THROUGH THE DAY TODAY. THE
FORWARD MOVEMENT OF THE FRONT WILL BE SLOW BECAUSE THE UPPER LEVEL
FLOW IS NEARLY PARALLEL TO THE FRONT.  DURING THE DAY TODAY...THE
RIGHT REAR QUADRANT OF A 120 KNOT 300 MB JET WILL ROTATE THROUGH THE
FORECAST AREA...INCREASING THE UPPER LEVEL DIVERGENCE AND CAUSING
FURTHER INTENSIFICATION OF STORMS. THE CAPE TODAY IS MAGINALLY
UNSTABLE WITH VALUES OF 500 TO 100 J/KG. THE SURFACE TO 3 KM
HELICITY VALUES SHOULD BE QUITE IMPRESSIVE...POSSIBLY IN THE 400 TO
600 M2/S2 RANGE ACROSS PORTIONS OF THE FORECAST AREA TODAY. THE
SEVERE RISK FOR TODAY WILL INCLUDE EVERYTHING FROM TORNADOES TO HAIL
TO DAMAGING STRAIGHTLINE WINDS.

AS THE SURFACE FRONT MOVES ACROSS THE FORECAST AREA TODAY THE RISK
OF SEVERE STORMS WILL END. SOME THUNDERSTORMS MAY PERSIST INTO THE
EARLY EVENING HOURS ACROSS EASTERN MISSISSIPPI AND ISOLATED LIGHT
SHOWERS WILL BE POSSIBLE ACROSS THE REGION TILL AROUND MIDNIGHT
AHEAD OF THE 500 MB TROUGH. AFTER MIDNIGHT...EXPECT CLEARING SKIES
WITH A COOL BUT SUNNY DAY ON FRIDAY. CLOUDS WILL INCREASE LATE
SATURDAY AHEAD OF ANOTHER FRONT WITH A CHANCE OF RAIN BY SATURDAY
NIGHT.

IN THE EXTENDED FORECAST SUNDAY THROUGH WEDNESDAY...AFTER A BRIEF
CHANCE OF RAIN SATURDAY NIGHT...A BIGGER RAIN EVENT IS SHAPING UP
FROM MONDAY NIGHT INTO CHRISTMAS CHRISTMAS EVE. ACCORDING TO THE
LATEST GFS MODEL RUN...CHRISTMAS EVE DAY COULD BE VERY WET IN MUCH
OF THE FORECAST AREA. RAIN MAY BE OUT OF THE AREA BY CHRISTMAS
DAY...BUT WILL KEEP CHANCE OF RAIN IN THE FORECAST FOR CHRISTMAS DAY
IN CASE THE SYSTEM SLOWS DOWN A BIT.

PRELIM NUMBERS...
JAN 64/40/59/34/63 92000
MEI 65/40/59/33/63 95000

.JAN...
AR...NONE.
LA...NONE.
MS...NONE.

15

ARZ074-075-LAZ007>009-015-016-023>026-MSZ018-019-025>066-072>074-
201200-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE JACKSON MS
0456 AM CST THU DEC 19 2002

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL MISSISSIPPI...
NORTHEAST LOUISIANA...AND EXTREME SOUTHEAST ARKANSAS

.DAY ONE...TODAY AND TONIGHT...

...THUNDERSTORMS...
SEVERE THUNDERSTORMS WILL BE POSSIBLE TODAY OVER THE ENTIRE
OUTLOOK AREA.  WIND GUSTS TO 60 MPH...DANGEROUS LIGHTNING AND
HEAVY RAIN CAN BE EXPECTED. ISOLATED TORNADOES WILL ALSO BE
POSSIBLE.

A STALLED BAND OF SHOWERS AND THUNDERSTORMS ACROSS THE DELTA
REGION THIS MORNING WILL GRADUALLY MOVE TO THE EAST ACROSS
NORTHEAST LOUISIANA AND MISSISSIPPI TODAY. A STRONG UPPER LEVEL
DISTURBANCE WILL MOVE OVER THE AREA ENHANCING THE DEVELOPMENT OF
SEVERE STORMS AND TORNADOES WITHIN THE BAND.

...FLOODING...
LOCALLY HEAVY RAINFALL WILL BE POSSIBLE TODAY...MAINLY ALONG AND
WEST OF A LINE FROM GRENADA MISSISSIPPI...TO YAZOO CITY TO
WINNSBORO LOUISIANA.
PONDING OF WATER ON STREETS...HIGHWAYS...CULVERTS AND OTHER LOW
LYING AREAS MAY OCCUR.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY...

...DAYS TWO AND THREE...
NO HAZARDOUS WEATHER IS EXPECTED THROUGH THE PERIOD.

...DAYS FOUR THROUGH SEVEN...
AN UPPER LEVEL TROUGH IS EXPECTED TO DEEPEN OVER TEXAS BY
TUESDAY.  AT THE SURFACE...A STRONG LOW PRESSURE AREA WILL
DEVELOP AHEAD OF THIS TROUGH.  THIS SURFACE LOW WILL EVENTUALLY
MOVE EAST INTO THE LOWER MISSISSIPPI RIVER VALLEY.  WITH AN
UNSTABLE AIRMASS EXPECTED TO BE IN PLACE...STRONG THUNDERSTORMS
COULD DEVELOP ACROSS EXTREME SOUTHEAST ARKANSAS...NORTHEAST
LOUISIANA AND MUCH OF MISSISSIPPI ON CHRISTMAS EVE.

.SPOTTER CALL TO ACTION STATEMENT...
THE ACTIVATION OF STORM SPOTTERS...HAM RADIO OPERATORS...AND
EMERGENCY MANAGEMENT PERSONNEL IN SUPPORT OF SEVERE WEATHER
OPERATIONS...WILL LIKELY BE REQUESTED TODAY.

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