039
AWUS01 KWNH 181945
FFGMPD
LAZ000-TXZ000-190145-
MESOSCALE PRECIPITATION DISCUSSION 0119
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
344 PM EDT SAT APR 18 2026
AREAS AFFECTED...SOUTHEAST TX...SOUTHWEST LA
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 181945Z - 190145Z
SUMMARY...POTENT THUNDERSTORMS CAPABLE OF PRODUCING >2"/HR
RAINFALL RATES OVER THE URBANIZED COMMUNITIES OF SOUTHEAST TX AND
SOUTHWEST LA COULD CAUSE LOCALIZED URBAN FLASH FLOODING.
DISCUSSION...VISIBLE SATELLITE AND DOPPLER RADAR SHOW A BUBBLING
FIELD OF CONVECTION OVER SOUTHEAST TX AND SOUTHWEST LA IN ADVANCE
OF AN APPROACHING STRONG COLD FRONT. ADDITIONAL SURFACE BASED
HEATING THIS AFTERNOON WILL YIELD OVER 1,500 J/KG OF MLCAPE ALONG
THE I-10 CORRIDOR. WINDS IN ADVANCE, AND IN WAKE, OF THE COLD
FRONT ARE NERLY WHILE WINDS WITHIN THE 700-200MB LAYER ARE FIRMLY
OUT OF THE WSW. THIS IS SUPPORTING EFFECTIVE BULK VERTICAL WIND
SHEAR LEVELS THAT THE RAP SUGGESTS COULD SURPASS 40 KTS. THIS
WOULD ALLOW FOR THUNDERSTORMS TO HAVE MORE LONGEVITY THAN TYPICAL
"POP-UP" OR "GARDEN VARIETY" STORMS. HRRR AND RAP AREA AVERAGED
SOUNDINGS SHOW WARM CLOUD LAYERS UP TO 12,000FT DEEP AND SKINNY
CAPE PROFILES THAT FOUND IN TYPICAL WARM RAIN PROCESSES. AS 850MB
AND 700MB WEAKEN OVER THE REGION THIS EVENING, THE CONCERN IS FOR
ADDITIONAL THUNDERSTORM DEVELOPMENT EITHER ALONG THE COLD FRONT OR
INDUCED BY THE GROWING COLD POOL.
GIVEN THE FAVORABLE THERMODYNAMIC ENVIRONMENT AND INCREASING PWS
THAT REACH 2.0" EAST OF HOUSTON THIS EVENING, THE CONCERN IS FOR
>2"/HR RAINFALL RATES THAT MANIFEST OVER URBANIZED ENVIRONMENTS.
THE 12Z HREF DOES SHOW LOW-CHANCE PROBABILITIES (10-30%) FROM THE
HOUSTON SUBURBS ON EAST INTO SOUTHWEST LA THIS AFTERNOON AND
EVENING. THE VAST MAJORITY OF THE EXPECTED RAINFALL OVER SOUTHEAST
TX AND SOUTHWEST LA THIS AFTERNOON IS WELCOMED (SEVERE AND EXTREME
DROUGHT FOR MANY), WHICH IS ALSO EVIDENT IN THE 1-HR FFGS THAT ARE
NO LOWER THAN 2" AREA WIDE. THAT SAID, THE POTENTIAL FOR
SLOW-MOVING AND REPEATING ROUNDS OF STORMS, COMBINED WITH
ANOMALOUS PWS AND AMPLE INSTABILITY ALOFT, COULD CAUSE LOCALIZED
FLASH FLOODING IN URBANIZED SETTINGS THAT CONTAIN A GREATER
CONCENTRATION OF HYDROPHOBIC SURFACES. LOW-LYING AREAS WITH POOR
DRAINAGE ARE ALSO SUSCEPTIBLE TO FLASH FLOODING THIS AFTERNOON.
MULLINAX
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...HGX...LCH...
ATTN...RFC...FWR...ORN...NWC...
LAT...LON 30589389 30569330 30069327 29629387 29209491
28939574 28839638 28939668 29259658 29709602
30369451
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