000
FOUS30 KWBC 190135
QPFERD

EXCESSIVE RAINFALL DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
934 PM EDT SAT MAY 18 2013

...VALID 03Z SUN MAY 19 2013 - 00Z MON MAY 20 2013...
...REFERENCE AWIPS GRAPHIC UNDER...DAY 1 EXCESSIVE RAINFALL...


SLIGHT RISK OF RAINFALL EXCEEDING FFG TO THE RIGHT OF A LINE FROM
30 NE TOR 35 E D07 10 E JMS CKN 20 WSW CWTX 15 E CWTX 30 E VWU
25 WNW GPZ 15 W LXL 20 NNE PQN 40 WNW YKN 40 SE ANW OGA
25 SE IBM 30 NE TOR.

STILL LITTLE CHANGE FM PREVIOUS THINKING..WITH LOW CONFIDENCE
CONTINUING.  HGT FALLS AND FVBL DIV ALOFT ASSOCTD WITH THE WRN
U.S. UPPER TROF WILL GENERATE A FAIRLY SIZABLE AREA OF
ASCENT..COINCIDING WITH A DEVELOPING LLJ ~30 KTS AND PW`S ~1.25"
(WHICH IS ABOUT 2 STD DEVIATIONS ABOVE THE NORM).
UNFORTUNATELY..THE 12Z AND EVEN 18Z MODEL QPFS CONTINUE TO DIFFER
SGFNTLY BTWN ONE ANOTHER..AS WELL AS SHOWING SGFNT RUN TO RUN
CHANGES.  AS A RESULT..THE ISSUED SLGT RISK FOR THE AREAS WILL
CONTINUE TO BE FAIRLY LARGE.  RNFL AMTS OF 1.50 TO 2.00 INCHES IN
A THREE HOUR PD WOULD SEEM QUITE POSSIBLE GIVE THE MSTR AND
FORCING INVOLVED..WITH TOTALS LIKELY TO APCH 4.00 INCHES THRU THE
PD OVR SPOTTY AREAS.


...ALABAMA/GEORGIA...

CANNOT RULE OUT THE POTENTIAL FOR REDVLPMNT OF CNVCTV RAINS LATER
TNGT AS A FVBL LLVL MSTR FLUX CONTINUES INTO THE BACKSIDE OF A
MID/UPR LVL COOL POCKET SUPPORTING A REGION OF ISENTROPIC LIFT.
AT THIS TIME WOULD FAVOR NRN AL AND W CNTRL GA FOR THE MOST
ORGANIZED SHWRS WITH THE MAIN CONCERN BEING THAT SHWRS COULD
REPEAT OVR AREAS SATURATED BY ACTVTY OVR THE PAST 12 HOURS.


...EXTREME NRN OK INTO CNTRL AND ERN KS...

BCMG MORE CONCERNED ABT THE POTNL FOR AT LEAST SOME LCLY HVY RAINS
OVRNGT FM EXTREME NRN OK INTO PORTIONS OF CNTRL AND ERN KS.  HGT
FALLS COMING OUT INTO THE PLAINS SHLD SUPPORT CONTD CONVECTIVE
DVLPMNT AHD OF DRYLN AND THE EVENTUAL PAC FNT AND GENLY N AND E OF
THE WK WNW-ESE ORIENTED SFC BNDRY IN PLACE FM SCNTRL KS INTO
WCNTRL AR.  GRIDDED DATA FM THE MDLS..AND ESP THE 18Z GFS..SHOWS A
VRY SLOLY PROGRESSIVE 50-60+ KTS OF SSWLY LLJ WHICH SHLD AID IN
THE DVLPMNT..WITH PWS INCREASING/POOLING TO NR OR ABV 1.50 INCHES
AS A RESULT OF THIS INFLO.  LRG SCALE LIFT WL ALSO BE HELPED BY
WHAT SHLD BE A VRY DIFL UPR FLOW REGIME.  FF GUIDANCE VALUES ARE
RATHER HI..BUT THE POTNL FOR LCL 1-2+ INCH RNFL AMTS IN AN HR OR
SO AND ISOLD 3+ INCH TOTALS RMNDR OF SAT NGT COULD CAUSE AT LEAST
SOME RUNOFF PROBS.

TERRY
$$