MESOSCALE PRECIPITATION DISCUSSION 0133
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
513 PM EDT WED APR 20 2016
 
AREAS AFFECTED...SOUTHWEST/CENTRAL LA...EXTREME SOUTHWEST MS 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 202110Z - 210000Z
 
SUMMARY...SLOW-MOVING SHOWERS AND THUNDERSTORMS OVER THE NEXT 2 TO
3 HOURS MAY RESULT IN SOME ADDITIONAL RUNOFF CONCERNS AND POSSIBLE
FLASH FLOODING.

DISCUSSION...LATE-DAY GOES-14 SRSO VIS IMAGERY SHOWS THE
PERSISTENCE OF SOME LOW LEVEL CLOUD STREETS OVER SOUTHERN LA OUT
AHEAD OF A RELATIVELY ORGANIZED AND SLOW-MOVING BAND OF
COLD-TOPPED CONVECTION. THIS SUGGESTS A CONTINUATION OF AN
UNSTABLE BOUNDARY LAYER...ALTHOUGH THE CLOUD TOP TEMPERATURES AS
PER IR SRSO IMAGERY HAVE BEGUN TO WARM JUST A TAD OVER THE LAST 15
TO 20 MINUTES. THE EXPERIMENTAL GLD-LIGHTNING DENSITY PRODUCT
SHOWS AN ENHANCED AREA OF STRIKE ACTIVITY NEAR LAKE CHARLES AND
ALONG A SW/NE AXIS ACROSS MOST OF SOUTHWEST LA AND UP TOWARD THE
BORDER WITH FAR SOUTHWEST MS. DUAL-POL RAINFALL RATES HAVE BEEN ON
THE ORDER OF 2 TO 2.5 INCHES/HR WITHIN THIS BAND OF CONVECTION
WHICH IS FOCUSING ALONG AND JUST AHEAD OF A LONG-LIVED OUTFLOW
BOUNDARY. PWATS AS PER THE BLENDED-TPW PRODUCT ARE ABOUT 1.5
INCHES WHICH IS SEEN NOSED SOUTH OUT OVER THE WESTERN GULF OF
MEXICO.

HRRR-TLE GUIDANCE SUGGESTS ANOTHER 2 TO 3 HOURS OF HEAVY RAINFALL
POTENTIAL WITH THIS BAND OF CONVECTION WITH LOCALIZED AMOUNTS OF 2
TO 4 INCHES THROUGH 00Z. THE SLOW MOVEMENT OF THE ACTIVITY AND
LOCALLY WET ANTECEDENT CONDITIONS WILL PROMOTE THE POTENTIAL FOR
RUNOFF PROBLEMS THROUGH EARLY EVENING...BEFORE THEN SEEING
CONDITIONS IMPROVE AS SURFACE-BASED INSTABILITY BEGINS TO
GRADUALLY WANE HEADING TOWARD SUNSET. WILL CONTINUE TO MONITOR.

ORRISON

ATTN...WFO...JAN...LCH...LIX...

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

LAT...LON   31379156 31119112 30299123 29619230 29629334 
            29799368 30249329 30769254