Severe Thunderstorm Warning 509, NWS Jackson, MS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
315 PM CDT THU JUN 19 2003

FORECAST CHALLENGES THIS PACKAGE...TIMING OF WEAK FRONTAL PASSAGE
FRIDAY...LOW TEMPS FRI AND SAT NIGHT...AND POPS THROUGH THE PERIOD.

CURRENTLY...WAT VAP IMAGERY SHOWS WEAK SHORTWAVE ENERGY LIFTING
NORTHEAST TOWARD THE SOUTHERN APPALACHIANS.  TEMPS ACROSS THE CWFA
HAVE RISEN INTO THE MIDDLE AND UPPER 80S WITH SCT CU/TCU DEVELOPING
AREA WIDE.  88D IMAGERY INDICATES WIDELY SCT SHRA AND TSRA
DEVELOPING...MAINLY EAST OF INTERSTATE 55...AND EXPECT SCT
DEVELOPMENT TO CONTINUE UNTIL SUNSET.

IN THE SHORT TERM...MODELS IN GOOD AGREEMENT WITH THE UPPER LEVEL
PATTERN...MOVING A CLOSED LOW FROM THE GREAT LAKES SOUTHEASTWARD TO
THE MID-ATLANTIC AND THEN NORTHEASTWARD OUT TO SEA.  AT THE
SFC...ETA AND MAV DIFFER SLIGHTLY ON JUST HOW FAR SOUTH THE SFC
FRONT WILL PUSH.  WITH MUCH OF THE UPPER LEVEL DYNAMICS WILL SHIFT
EASTWARD BY FRIDAY NIGHT...WILL SIDE WITH THE ETA WHICH PLACES THE
FRONT NEAR THE GULF COAST.  FOR FRIDAY...WILL LOWER POPS IN NORTHERN
ZONES AS FRONT WILL MAKE IT THROUGH THE REGION BEFORE THE BEST
HEATING.  AMPLE HEATING WILL OCCUR AHEAD OF THE FRONT IN CENTRAL AND
SOUTHERN ZONES AND WILL MAINTAIN CHANCE POPS DURING THE AFTERNOON
AND EVENING.  STABILITY AND MOISTURE INDICES SHAPE UP AS
FOLLOWS...LIS LESS THAN -3...SBCAPE IN EXCESS OF 2000 J/KG...SFC
DEWPOINTS IN THE LOW TO MID 70S AND KIS GREATER THAN 32.  PRIMARY
RISK WILL BE HEAVY DOWNPOURS...HOWEVER CANNOT RULE OUT AN ISOLATED
SVR STORM...EMPHASIS ON ISOLATED.

DRY AIR BEHIND THIS FRONT WILL ALLOW LOWS TO FALL INTO THE 60S
EVERYWHERE EXCEPT SOUTHERN ZONES.  COOLEST TEMPS...MID 60S...WILL BE
CONFINED TO THE NE ZONES.  WITH FRONT SOUTH OF THE AREA ON
SATURDAY...EXPECT PARTLY CLOUDY CONDITIONS WITH ONLY SLIGHT CHANCE
POPS IN THE SOUTHERN ZONES...CLOSE TO THE SFC FRONT.  LOWS ON
SATURDAY NIGHT WILL BE A BIT TRICKY.  ETA BEGINS TO SLOWLY MOVE THE
SFC FRONT NORTHWARD...NORTHEAST AND EASTERN ZONES WILL DIP INTO THE
MID 60S...HOWEVER NOT QUITE SURE HOW LOW CENTRAL AND WESTERN ZONES
WILL DROP.  IF THE FRONT IS A BIT SLUGGISH...WOULDN/T BE SURPRISED
TO SEE MID 60S IN THE METRO AREA.

ON SUNDAY...ETA AND MAV AGREE THAT THE SFC FRONT WILL SLOWLY
TRAVERSE NORTHWARD AND UPPER LEVEL RIDGING WILL BUILD INTO THE
REGION FROM THE WEST.  BOTH ETA AND MAV MOVE A WEAK SHORTWAVE TROUGH
INTO THE REGION IN NW FLOW...HOWEVER ONLY ETA PRODUCES ANY PRECIP.
AT THIS TIME WILL BE CONSERVATIVE AND NOT INCREASE POPS ON
SUNDAY...MAINTAINING SLIGHT CHANCE POPS OVER SOUTHERN
ZONES...HOWEVER FUTURE MODEL RUNS WILL NEED TO BE MONITORED FOR THE
POTENTIAL OF ELEVATED TSRA NORTHEAST OF THE FRONT.

LEANED TOWARD MAV TEMPS THIS PACKAGE.

IN THE EXTENDED...MED RANGE MODELS IN FAIR AGREEMENT THROUGH THE
PERIOD.  MOST PROMINENT LARGE SCALE FEATURE TO DOMINATE OUR WEATHER
WILL BE A WEAK UPPER RIDGE EXPECTED TO EXPAND OVER THE SOUTHERN
PLAINS AND LOWER MS RIVER VALLEY.  BY MIDWEEK THE GFS...EURO AND
UKMET TRANSLATE A TROUGH THROUGH THE INTERMOUNTAIN WEST INTO THE
PLAINS.  AT THIS POINT...EXPECT THIS FEATURE TO REMAIN NORTHWEST OF
OUR AREA...A SURE SIGN THAT WE ARE FINALLY TRANSITIONING INTO A MORE
SUMMERLIKE PATTERN.

DESPITE UPPER RIDGING AND A SFC HIGH PRESSURE LOCATED JUST TO THE
EAST OF THE AREA...WILL CONTINUE TO INCLUDE NEAR CLIMO CHANCES OF
TSRA...MAINLY DURING THE AFTERNOON.

PRELIM NUMBERS:
JAN BB 071/088 066/090 066 00232
    BBBBB 090/071 090/072 091/072 091/072 092 11122233333
MEI BB 071/088 066/090 064 00231
    BBBBB 090/070 090/071 090/071 090/071 091 11122233333

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

GAGAN

ARZ074-075-LAZ007>009-015-016-023>026-MSZ018-019-025>066-072>074-
201855-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE JACKSON MS
155 PM CDT THU JUN 19 2003

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

.DAY ONE...TONIGHT AND FRIDAY...

...THUNDERSTORMS...
SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP
THURSDAY AFTERNOON AND EVENING ACROSS MUCH OF THE LOWER
MISSISSIPPI VALLEY. A FEW OF THESE STORMS ALONG AND EAST OF THE
INTERSTATE 55 CORRIDOR IN CENTRAL AND SOUTHERN MISSISSIPPI COULD
BECOME LOCALLY SEVERE. THE MAIN RISK WITH INTENSE STORMS WILL BE
HIGH WINDS AND HEAVY RAINFALL. THURSDAY NIGHT ANY LINGERING
SHOWERS AND STORMS SHOULD ONLY AFFECT LOCATIONS SOUTH OF
INTERSTATE TWENTY...BUT THESE WILL REMAIN BELOW SEVERE LIMITS. ON
FRIDAY...ATMOSPHERIC INSTABILITY ALONG AND SOUTH OF FRONTAL
BOUNDARY WILL BRING MORE SCATTERED SHOWERS AND
STORMS...ESPECIALLY DURING THE AFTERNOON...TO LOCATIONS IN
NORTHEAST LOUISIANA AND SOUTHERN MISSISSIPPI. AT THIS
TIME...THERE LOOKS TO BE INSUFFICIENT INGREDIENTS FRIDAY TO BRING
STORMS THAT FORM UP TO SEVERE LEVELS.

THROUGH THURSDAY EVENING...AN UPPER LEVEL TROUGH WILL REMAIN OVER
THE SOUTHEAST UNITED STATES. WEAK DISTURBANCES ALOFT...ALONG WITH
BOUNDARIES NEAR THE SURFACE...WILL BE THE FOCUS FOR THUNDERSTORMS
OVER NORTHEAST LOUISIANA...SOUTHEAST ARKANSAS...AND CENTRAL AND
SOUTHERN MISSISSIPPI. ALTHOUGH THE ATMOSPHERE WILL BECOME VERY
UNSTABLE ACROSS THE ENTIRE AREA THIS AFTERNOON...STRONGER MID
LEVEL WINDS LOCATED OVER CENTRAL AND EASTERN MISSISSIPPI SHOULD
KEEP THE RISK OF POTENTIALLY DAMAGING STORMS LIMITED TO THIS
PORTION OF THE LOWER MISSISSIPPI VALLEY.

...FLOODING...
SHOWERS AND THUNDERSTORMS THAT DEVELOP THURSDAY WILL LIKELY
PRODUCE VERY HEAVY RAIN. THE HEAVY RAINFALL OVER THE THE PAST
SEVERAL DAYS HAS KEPT SOILS AROUND THE REGION NEARLY SATURATED
AND ANY ADDITIONAL RAINFALL WILL ONLY AGGRAVATE THE SITUATION.
THE BRIEF HEAVY DOWNPOURS FROM THE SHOWERS AND THUNDERSTORMS WILL
LIKELY PRODUCE PONDING OF WATER ON ROADWAYS AND MINOR FLOODING OF
SMALL CREEKS AND STREAMS.

THE MOISTURE CONTENT OF THE ATMOSPHERE WILL DECREASE FROM THE
NORTH FRIDAY...CONFINING THE TROPICAL AIRMASS TO SOUTHERN
MISSISSIPPI BY FRIDAY AFTERNOON. THEREFORE...THE POTENTIAL FOR
HEAVY RAIN FRIDAY WILL SHIFT TO AREAS ALONG AND SOUTH OF
INTERSTATE TWENTY. IN THESE LOCATIONS....HEAVY DOWNPOURS FROM
FLOODING MAY PRODUCE ISOLATED INCIDENTS OF FLOODING AND PONDING
OF WATER UPON ROAD SURFACES.

.DAYS TWO THROUGH SEVEN...FRIDAY NIGHT THROUGH THURSDAY...

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER CALL TO ACTION STATEMENT...
THE ACTIVATION OF STORM SPOTTERS...HAM RADIO OPERATORS...AND
EMERGENCY MANAGEMENT PERSONNEL IN SUPPORT OF SEVERE WEATHER
OPERATIONS...IS NOT ANTICIPATED THROUGH TONIGHT.

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