MESOSCALE PRECIPITATION DISCUSSION 0319
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1244 PM EDT MON JUN 18 2018

AREAS AFFECTED...SOUTHEAST TEXAS AND SOUTHWEST LOUISIANA

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 181643Z - 182243Z

SUMMARY...LOCALLY HEAVY DOWNPOURS ARE EXPECTED THIS AFTERNOON
ACROSS THE NORTHERN GULF COAST OF TEXAS AND ADJACENT COASTAL PLAIN
AND EXTENDING EASTWARD ACROSS MUCH OF SOUTH CENTRAL LOUISIANA. 
RAINFALL RATES OF 2+ INCHES PER HOUR ARE POSSIBLE WITH THE
HEAVIEST CONVECTION.

DISCUSSION...A MID TO UPPER LEVEL LOW SLOWLY MEANDERING OVER THE
WESTERN GULF OF MEXICO IS CAUSING ENHANCED LOW LEVEL MOISTURE
CONVERGENCE OVER THE COASTAL WATERS AND ADJACENT COASTAL PLAINS OF
TEXAS AND LOUISIANA.  MULTIPLE BANDS OF HEAVY CONVECTION MOVING
TOWARDS THE NORTHWEST ARE EXPECTED TO TRAIN OVER SOME AREAS
REPEATEDLY THROUGH THE EARLY TO MID AFTERNOON HOURS. 

FACTORS SUPPORTING THIS HEAVY RAINFALL EVENT ARE THE HIGHLY
ANOMALOUS PWS NEAR 2.5 INCHES, 30 TO 40 KNOTS OF SUSTAINED 850MB
MOISTURE TRANSPORT, 1000-1500 J/KG OF MLCAPE, AND VERY SLOW
MOVEMENT OF THE MAIN DISTURBANCE OVER THE GULF.  ONE OF THE
MITIGATING FACTORS IS THE RELATIVELY HIGH FLASH FLOOD GUIDANCE
OWING TO RECENT DRY CONDITIONS OVER THIS REGION, SO FLASH FLOODING
IS CONSIDERED POSSIBLE IN THOSE AREAS THAT HAVE VERY HIGH RAINFALL
RATES.

THE MAJORITY OF THE HIGH RES MODEL GUIDANCE IS INDICATING
SCATTERED RAINFALL TOTALS ON THE ORDER OF 1 TO 3 INCHES, WITH
ISOLATED TOTALS OF 4 INCHES OR MORE POSSIBLE THROUGH 23Z.  THE
HRRR IS INDICATING THE HEAVIEST RAINFALL NEAR AND JUST WEST OF THE
GREATER HOUSTON AREA, WITH SOME DIFFERENCES IN THE GUIDANCE ON HOW
FAR INLAND THESE RAIN BANDS GO THIS AFTERNOON. 

D. HAMRICK

ATTN...WFO...CRP...HGX...LCH...LIX...

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

LAT...LON   30739325 30709217 30489117 30029032 29369025
            28949065 29099139 29369211 29599302 29559391
            29159478 28749532 28479588 28539625 28759646
            29409644 30109560 30589455