Severe Thunderstorm Warning 654, NWS Jackson, MS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE JACKSON MS
350 AM CST WED NOV 8 2000

...HEAVY RAIN THREAT GROWS FOR CWFA...ISOLATED SEVERE POSSIBLE...
STALLED FRONT MOVING SLOWLY NWWD SINCE SUNSET WITH VERY JUICY L-M70S
DEWPOINTS NOW ALONG AND S OF THE NATCHEZ TRACE. VAD WINDS HERE
SHOWING BOUNDARY HAS ABOUT ERODED LOCALLY WITH MOST ELEVATED
CONVECTION N OF THE BOUNDARY MOVING STEADILY NWD. ISOLATED STRONG
CELLS IN THE DELTA APPEAR TO BE LOSING THEIR PUNCH AT THE MOMENT BUT
WILL REMAIN ALERT WITH WW/S 784&783. AVN/ETA CAPES NOW PROGGED TO
REACH 1000-1800J/KG HOWEVER THESE MAY BE TOO LOW SINCE WARM SECTOR
AIRMASS APPEARS TO BE MORE UNSTABLE THAN MODELS GIVING CREDIT FOR.

MODELS VERY SIMILAR WITH INCREASING LOW LEVEL WARM ADVECTION AHEAD
OF A SURFACE WAVE PROGGED TO MOVE ONSHORE NEAR KLCH BY 18Z MOVING TO
NEAR KGWO BY 06Z. THE NOSE OF 850MB SLY JET AXIS OVER WRN LA SHOWS
UP WELL AT WINFIELD PROFILER WITH 45 KTS AND THIS AXIS SHOULD PUSH
EWD ALONG I-55 ABOUT 03Z. LOOK FOR TRAINING TSRA TO CONTINUE TODAY
FROM CENTRAL LA TO MS DELTA REGION AS SURFACE LOW APPROACHES FROM
THE SW.  ONCE THIS LOW CROSSES N MS FROM 06-12Z THURSDAY...RAINFALL
RATES SHOULD DIMINISH GREATLY FROM THE SW. RAINS EXPECTED TO END IN
ERN HALF OF MS BY 18Z THURSDAY.

A CLOSED UPPER LOW NEAR THE RIO GRANDE BEGINS KICKING OUT TONIGHT
AND THEN ACCELERATING NEWD THURSDAY. AVN(AND EVEN ETA) DELIVER 500MB
VORTICITY FIELDS OF 35-40 UNITS ACROSS THE ARKLATEX TO WRN KY
THURSDAY MORNING WHICH SENDS PRIMARY RAIN BAND EWD INTO AL/GA. AVN
AIRMASS ANALYSIS IN THE WARM SECTOR AHEAD OF THIS YIELDS: TOTALS
45-50... LIFTED INDICES MINUS 4-5.....5.5-6.5C MID LEVEL LAPSE
RATES...ALSO ETA BRN SHEAR 40-100...EHI 1.5-2.5 AND STORM RELATIVE
HELICITIES 160-300 IN THE RIGHT ENTRANCE REGION OF 120-130KT 300MB
JET. AT THIS TIME...WILL KEEP HEAVY RAIN MENTION IN ZONES AND WAIT
FOR MORNING MODEL RUNS BEFORE INCLUDING SEVERE THREAT IN PORTIONS OF
ERN MS FOR TONIGHT.

TEMPERATURES FINALLY BECOME MORE SEASONAL FRIDAY WITH DRYING OUT
PATTERN FOR MOST OF WEEKEND.

24 HR QPF DISCUSSION: MODELS CONSISTENTLY DEVELOP HEAVIEST RAINFALL
IN CLOSE PROXIMITY OF LOW PRESSURE CENTER. SYSTEM MOVES NORTHEAST
FROM LA INTO OH RIVER VALLEY...DRAGGING FRONT TO AROUND GA-FL BY 48
HRS. MODELS CRANK OUT TOTAL RAINFALL AMOUNTS GREATER THAN 2" OVER LA
INTO MS. PRECIP WATER VALUES AOA 1.5" OVER AREA THIS MORNING...
INCREASE TO OVER 2" IN AVN OVER CWFA BY 18Z...WITH JUST NGM SLIGHTLY
DRIER. VALUES REMAIN HIGH THROUGH 12Z THU. WITH RAIN/THUNDERSTORMS
LIKELY ...WILL ACCEPT NCEP VALUES. LOCALLY HEAVY RAINFALL MAY
DEVELOP IN STRONGER STORMS...WHICH COULD PRODUCE SOME PONDING.
TOTALS FOR WED WILL RANGE TO NEAR 3" OVER NE LA/WEST MS TO AROUND 1"
SE MS.

EXTENDED...SHORTWAVE RIDGE DOMINATES THURSDAY NIGHT THROUGH SATURDAY
WITH ZONAL W-E FLOW SETTING UP FOR SUNDAY/MONDAY BENEATH 95-105KT
300MB AXIS. LIMITED RETURN FLOW IN THE LOW LEVELS BECOMING MORE
LIKELY ON LATEST MRF AND UKMET ALSO TRENDING WEAKER WITH THE NEXT
SYSTEM.  NOGAPS ALSO HOLDING ON TO DRIER SCENARIO GOING INTO DAYS
6&7.

.PRELIM NUMBERS...
JAN 76/60/65/45 +96-
MEI 78/64/69/47 6981

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