MESOSCALE PRECIPITATION DISCUSSION 0157
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1054 AM EDT THU MAY 17 2018

AREAS AFFECTED...LOWER TO MID-MISSISSIPPI VALLEY

CONCERNING...HEAVY RAINFALL

VALID 171452Z - 172000Z

SUMMARY... SLOW MOVING STORMS IN AND AROUND THE LOWER TO MIDDLE
MISSISSIPPI VALLEY WILL CONTINUE TO POSE A FLASH FLOOD THREAT OVER
THE NEXT FEW HOURS WITH LOCALIZED HEAVY RAINFALL OF 3-5 INCHES
POSSIBLE THROUGH 21Z.

DISCUSSION...GOES 16 MID-LEVEL WATER VAPOR IMAGERY SHOWED A SLOW
MOVING VORTICITY CENTER OVER NORTHEASTERN ARKANSAS...EMBEDDED
WITHIN A LARGER SCALE UPPER TROUGH AXIS. RADAR IMAGERY THROUGH 14Z
SHOWED SLOW MOVING CONVECTION NORTHEAST OF THE VORTICITY CENTER
WITH KNQA DUAL POL ESTIMATES OF 2+ IN/HR OVER WESTERN GREENE AND
CRAIGHEAD COUNTIES. THE REGION WAS LOCATED ALONG THE WESTERN EDGE
OF A RAP-ESTIMATED MLCAPE GRADIENT WITH LOCALLY HIGHER
PRECIPITABLE WATER VALUES SAMPLED BY A GPS SITE ALONG THE
ARKANSAS/MISSISSIPPI BORDER AT 13Z READING 1.69 INCHES. 850 MB
WINDS SHOWED LOCALIZED CONVERGENCE OVER NORTHEASTERN ARKANSAS WITH
A SOUTHEASTERLY COMPONENT NEAR 15 KT PER KNQA VAD WIND PLOT.

SHORT TERM RAP FORECASTS SHOW THE DEVELOPMENT OF A SECOND
VORTICITY CENTER OVER NORTH-CENTRAL MISSISSIPPI BY 17Z...WHILE
MAINTAINING THE CURRENT VORTICITY CENTER IN NORTHEASTERN ARKANSAS
INTO THE EARLY AFTERNOON. SLOW MOVEMENT OF CONVECTION BETWEEN
THESE TWO FEATURES IS EXPECTED AND AS DAYTIME HEATING COMMENCES
ALLOWING INCREASES IN MLCAPE INTO THE EARLY AFTERNOON. ADDITIONAL
CONVECTION IS EXPECTED TO FORM IN THE VICINITY OF THE TWO
VORTICITY CENTERS AND GIVEN LOCAL EXCEEDANCE OF 850 MB FLOW
COMPARED TO LFC-EL MEAN-LAYER FLOW...SLOW MOVING/REPEATING CELLS
ARE EXPECTED ALONG WITH POSSIBLE FLASH FLOODING.

OTTO

ATTN...WFO...JAN...LSX...LZK...MEG...PAH...SGF...

ATTN...RFC...LMRFC...SERFC...

LAT...LON   37469079 37459016 37308972 37068938 36708926
            36218921 35688924 35238920 34858892 34398862
            34158852 33808847 33298855 32938892 32838973
            32979037 33759101 34519158 35229189 36069205
            36949160