Severe Thunderstorm Warning 637, NWS Jackson, MS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
315 PM CDT WED SEP 20 2000

88D INDICATING SCATTERED SHOWERS FIRING OVER MOST OF THE CWFA IN THE
MOISTURE LADEN AIRMASS. DEWPOINTS HAVE RISEN STEADILY FROM
YESTERDAYS LOWER TO MID 50S VALUES TO UPPER 60S TO LOWER 70S OVER
MOST AREAS. PWATS HAVE RISEN FROM JUST UNDER AN INCH FROM YESTERDAY
TO AROUND AN INCH AND A HALF. FRONTAL BOUNDARY IS FROM KFAM TO KFSM
TO NEAR KSJT AND MOVING SOUTHEAST.

THE FIRST PART OF THE FORECAST WILL BE CONCERNED WITH THE COLD FRONT
MOVING OVER THE CWFA DURING THE EARLY MORNING HOURS ON THURSDAY. THE
SECOND PART OF THE FORECAST WILL BE CONCERNED WITH THE TWO SYSTEMS
IN THE GULF OF MEXICO...AND WHERE THEY TRACK.

COLD FRONT SHOULD BE ALONG THE MISSISSIPPI RIVER SOMETIME BETWEEN
00Z AND 06Z ON THURSDAY. SCATTERED SHOWERS AND THUNDERSTORMS WILL
CONTINUE TO DEVELOP OUT ALONG AND AHEAD OF THE FRONT WHERE THE BEST
MOISTURE AND INSTABILITY EXIST. FRONT IS HARD TO FIND ON THE SURFACE
ANALYSIS BY 1Z THURSDAY...BUT MOISTURE IS STILL CONVERGING ALONG THE
WEAK BOUNDARY. BY 00Z FRIDAY...FRONT LOOKS TO HAVE BECOME DIFFUSE
AND THE TWO SYSTEMS IN THE GULF ARE STARTING TO BE A FACTOR.

THE FORECAST FOR THE LATTER HALF OF THE PERIOD WILL DEPEND ON THE
TRACK OF TD #12 AND THE CLUSTER OF SHOWERS AND THUNDERSTORMS OVER
THE WESTERN GULF. TD #12 (OR REMNANTS OF) ARE CURRENTLY FORECAST TO
SLIDE JUST EAST OF THE FORECAST AREA. ABOUT 6 HOURS LATER...THE
CLUSTER OF SHOWERS AND THUNDERSTORMS OVER THE WESTERN GULF IS
PROGGED TO MOVE IN OVER SOUTHEAST TX AND LOUISIANA. THIS SYSTEM IS
FORECAST TO AFFECT PORTIONS OF THE SOUTHWESTERN CWFA ON/BY FRIDAY
NIGHT. A LOT OF UNCERTAINTY WILL EXIST WITH BOTH OF THESE
SYSTEMS...SO AM RELUCTANT TO GO LIKELY/CATEGORICAL POPS THAT THE AVN
IS FORECASTING...ESPECIALLY SINCE THEN ETA SEEMS TO HAVE A BETTER
HANDLE ON THE CURRENT SITUATION IN THE GOM. THE DIRECTION OF THE
SLIGHTLY MORE CONSERVATIVE MOS NUMBERS LOOK LIKE THE WAY TO GO. NEXT
SHIFTS WILL HAVE TO CLOSELY MONITOR THE SITUATION IN THE GULF OF
MEXICO AND ADJUST THE FORECASTS ACCORDINGLY.

IN THE EXTENDED: ANOTHER COLD FRONT IS FORECAST TO APPROACH THE AREA
LATE SATURDAY INTO SUNDAY. WILL KEEP MENTION OF CHANCE POPS IN THE
EXTENDED.

QPF DISCUSSION: AN UNSTABLE AIR MASS AND ABUNDANT LOW LEVEL MOISTURE
WILL PRODUCE SCATTERED SHOWERS AND THUNDERSTORMS OVER MOST AREAS
DURING THE AFTERNOON AND EVENING. CONVECTION WILL DECREASE AROUND
SUNSET BUT AN APPROACHING COLD FRONT WILL MAINTAIN THE CHANCE OF
PRECIP OVER NRN ZONES THROUGH THROUGH THE NIGHT. LIGHT POST FRONTAL
PRECIP IS POSSIBLE NRN ZONES THU BUT SCATTERED SHOWERS AND
THUNDERSTORMS ARE EXPECTED AGAIN THRU CENTRAL AND SRN AREAS ALONG
AND S OF THE FRONTAL BOUNDARY. AGREE WITH NCEP TREND OF PRECIP MAX N
AND S.

PRELIM NUMBERS...
JAN  068/082/066/085 4534
MEI  069/083/065/085 4433

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