MESOSCALE PRECIPITATION DISCUSSION 0089
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
500 PM EDT FRI MAR 18 2016
 
AREAS AFFECTED...CENTRAL/EASTERN LA...CENTRAL/SOUTHERN MS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 182055Z - 190100Z
 
SUMMARY...HEAVY SHOWERS AND THUNDERSTORMS...WITH A FEW
CELL-MERGERS AND INTENSE RAINFALL RATES MAY CAUSE SOME FLASH
FLOODING GIVEN THE WET ANTECEDENT CONDITIONS.

DISCUSSION...IR SATELLITE IMAGERY SHOWS MULTIPLE CLUSTERS OF
COOLING CONVECTIVE TOPS OVER PORTIONS OF FAR EASTERN LA AND INTO
CENTRAL/SOUTHERN MS. MANY OF THESE AREAS HAVE ALREADY SEEN PLENTY
OF HEAVY RAINFALL OVER THE LAST WEEK...AND WITH SUCH WET
ANTECEDENT CONDITIONS...ANY ADDITIONAL HEAVY RAINS WILL RISK
CAUSING ADDITIONAL FLASH FLOODING.

THE ONGOING CONVECTION IS BEING FACILITATED BY PROXIMITY OF A
STATIONARY FRONT ALONG WITH A POOL OF WEAK INSTABILITY ALONG IT.
MEANWHILE...A SHORTWAVE EJECTING EAST INTO THE LOWER MS VALLEY IS
PROVIDING SOME LARGER SCALE ASCENT OVER THE REGION TO ALLOW
CONVECTIVE TOPS TO GROW AND EXPAND IN COVERAGE. MUCAPE VALUES ARE
1000 TO 2000 J/KG LOCALLY...WITH EVEN STRONGER INSTABILITY FOCUSED
FARTHER SOUTHWEST TOWARD THE WESTERN GULF COAST REGION WHERE
DIABATIC HEATING HAS BEEN STRONGER.

GPS PWATS OVER THE THREAT AREA ARE GENERALLY 1.25 TO 1.5
INCHES...AND THIS MOISTURE COUPLED WITH MORE VIGOROUS CONVECTIVE
GROWTH OVER THE NEXT COUPLE OF HOURS IS EXPECTED TO YIELD RAINFALL
AMOUNTS AS HIGH AS 1.5 INCHES/HR. THESE AMOUNTS MAY APPROACH 2
INCHES/HR GIVEN A LIKELIHOOD OF A FEW CELL-MERGERS AND
OVERSHOOTING TOPS.

HIRES GUIDANCE STRONGLY SUGGESTS THE CONVECTION TENDING TO WANE A
BIT AFTER 00Z WITH THE LOSS OF DIURNALLY HEATING...HOWEVER THERE
MAY BE ADDITIONAL CONVECTION LATER IN THE EVENING OR OVERNIGHT
GIVEN UPSTREAM HEIGHT FALLS/SHORTWAVE ENERGY THAT WILL BE ARRIVING
WHICH WILL PROVIDE A STRONGER DYNAMIC FOCUS. WILL CONTINUE TO
MONITOR.

ORRISON

ATTN...WFO...JAN...LCH...LIX...MOB...SHV...

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

LAT...LON   32968905 32328858 31678855 31218921 30818991 
            30279110 30239234 30399266 30719274 31399224 
            32029135 32469071 32889014