MESOSCALE PRECIPITATION DISCUSSION 0101
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
439 PM EDT SAT APR 14 2018

AREAS AFFECTED...FAR SERN LA /SRN MS INTO CNTRL AL

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 142035Z - 150200Z

SUMMARY...A TRAINING AXIS OF HEAVY RAIN IS EXPECTED TO PRODUCE 3-6
INCHES OF RAIN FROM EXTREME SERN LA...SRN MS INTO CNTRL AL. RAIN
RATES OF 1.5 TO 2.5 IN/HR CAN BE EXPECTED WHICH ARE LIKELY TO
PRODUCE FLASH FLOODING...SOME OF WHICH COULD BE SIGNIFICANT.

DISCUSSION...TRENDS IN RADAR REFLECTIVITY OVER THE PAST COUPLE OF
HOURS HAVE SHOWN A SIGNIFICANT SLOWING OVER SRN MS WITH THE
LEADING EDGE OF A CONVECTIVE LINE WHICH STRETCHED FROM CNTRL AL
THROUGH FAR SERN LA AT 20Z. THIS SLOWING IS IN RESPONSE TO AN
APPROACHING MID-UPPER LEVEL TROUGH AXIS CURRENTLY MOVING THROUGH
W-CNTRL TX AS DEPICTED ON WATER VAPOR SATELLITE IMAGERY. OBSERVED
RAINFALL RATES WITHIN THE CORE OF THE CONVECTIVE LINE OVER THE
PAST COUPLE OF HOURS HAVE AVERAGED BETWEEN 1-2 IN/HR...BUT DUAL
POL ESTIMATES HAVE PEAKED AS HIGH AS 2.5 IN/HR AS DEPICTED OVER
SRN STONE COUNTY IN SRN MS AT 20Z.

AS THE TROUGH AXIS OVER TX CONTINUES TO SWING EAST OVER THE NEXT
3-6 HOURS...MID-UPPER LEVEL FLOW WILL BACK...ALLOWING FOR
INCREASED DIVERGENCE AND DIFFLUENCE ALOFT OVER THE CNTRL GULF
COAST. INFRARED SATELLITE AND LIGHTNING DATA OVER THE NRN GULF
SHOW THE LINE OF CONVECTION CONTINUING SOUTHWARD TO ABOUT 27N
92W...WITH A PIVOT POINT OVER FAR SERN LA. AHEAD/NORTH OF THIS
PIVOT POINT IS EXPECTED TO BE THE GREATEST AREA OF CONCERN AS THE
CONVECTIVE LINE STALLS OR ONLY SLOWLY EDGES EASTWARD OVER THE NEXT
FEW HOURS WITH THE POTENTIAL FOR 3-6 INCHES WHERE THE AXIS STALLS
THE LONGEST.

THE HRRR AND EXPERIMENTAL HRRR HAVE BEEN HANDLING THE EVENT
REASONABLY WELL TODAY...HOWEVER THEY HAVE BEEN CONSISTENTLY 2-4
HOURS SLOW. ADJUSTING FOR THIS GAP IN TIME...THE PAST SEVERAL HRRR
RUNS HAVE FORECAST RAINFALL TOTALS OF 3-6 INCHES...SOMETIMES
HIGHER...STRETCHING FROM FAR SRN MS INTO CNTRL AL. DANGEROUS FLASH
FLOODING APPEARS LIKELY.

OTTO

ATTN...WFO...BMX...HUN...JAN...LIX...MOB...

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

LAT...LON   34948591 34828567 34478557 34008552 33398556
            32258595 30618719 30008842 29318934 29509018
            30258990 31168917 32058817 32928747 34008700
            34848641