986
AWUS01 KWNH 011749
FFGMPD
TXZ000-012250-
MESOSCALE PRECIPITATION DISCUSSION 0568
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
148 PM EDT TUE JUL 01 2025
AREAS AFFECTED...SOUTH TEXAS
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 011750Z - 012250Z
SUMMARY...SCATTERED SHOWERS AND THUNDERSTORMS MOVING
NORTH-NORTHWESTWARD INTO SOUTH TEXAS ARE CAPABLE OF PRODUCING
ISOLATED INSTANCES OF FLASH FLOODING AND 2-3"/HR RATES THROUGH AT
LEAST EARLY THIS EVENING.
DISCUSSION...LATEST RADAR AND SATELLITE IMAGERY DEPICTS
NORTH-SOUTH BANDS OF TROPICAL DOWNPOURS STREAMING NORTH-NORTHWEST
INTO SOUTH TEXAS FROM THE NORTHERN GULF COAST OF MEXICO. THESE
THUNDERSTORMS ARE OCCURRING ON THE NORTHWEST PERIPHERY OF A
MID-LEVEL LOW CHURNING OVER NORTH-CENTRAL BARRY (CAN BE TRACKED TO
THE REMNANTS OF FORMER T.S. BARRY). MAXIMUM ESTIMATED HOURLY
RAINFALL RATES FROM MRMS ARE AROUND 2-2.5" OVER THE LAST HOUR OR
SO, WITH 1.55" RECORDED AT THE BROWNSVILLE INTERNATIONAL AIRPORT
OVER THE LAST 3 HOURS. WHILE THIS INITIAL BAND APPEARS TO HANG UP
ALONG THE COAST, A SEPARATE ONE APPROACHING FROM FAR NORTHEAST
MEXICO MAY PROVIDE GREATER COVERAGE OF HEAVY RAINFALL THIS
AFTERNOON BASED ON RECENT RADAR SCANS AND STRONG SOUTHERLY 850-700
FLOW AROUND 20-25 KTS. THIS IS ALLOWING PWS TO REMAIN WELL ABOVE
WHAT'S NECESSARY FOR INTENSE RAINFALL RATES AS VALUES CLIMB TO
NEAR 2.5" (OVER THE 95TH CLIMATOLOGICAL PERCENTILE PER THE 00Z
ECENS). ADDITIONALLY MLCAPE VALUES OF 1000 J/KG REMAIN JUST INLAND
FROM THE GULF AS 2000 J/KG LINGER IN THE INFLOW REGION OVER THE
FAR WESTERN GULF. EVEN THOUGH STORM MOTIONS MAY BE FAST AND ON A
NORTH-NORTHWESTERLY DIRECTION, UPWIND PROPAGATION VECTORS ARE WEAK
AND MAY LEAD TO BACKBUILDING TOWARDS THE HIGHER INSTABILITY OVER
THE WESTERN GULF. THIS SUPPORTS AN ENVIRONMENT FOR ADDITIONAL
HEAVY RAINFALL THAT MAY COMPOUND TO LEAD TO ISOLATED FLASH
FLOODING CONCERNS OVER A REGION WITH RELATIVELY HIGH FFG.
3-HR FFG IN FAR SOUTH TEXAS REMAINS AROUND 3", LOCALLY LOWER ALONG
THE RIO GRANDE VALLEY. EVEN THOUGH CAMS ARE HIGHLY UNCERTAIN
REGARDING THE NORTHWARD EXTENT OF HEAVIEST THUNDERSTORMS, 12Z HREF
PROBS OF AT LEAST 3" IN 6-HRS (ENDING 21Z) ARE AROUND 30% FOR THE
SOUTHERN RIO GRANDE VALLEY REGION OF SOUTH TEXAS. THIS AGAIN WHEN
COMBINED WITH CURRENT RADAR/SATELLITE SUPPORTS THE POTENTIAL FOR
LOCALIZED INSTANCES OF FLASH FLOODING.
SNELL
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...BRO...CRP...
ATTN...RFC...FWR...NWC...
LAT...LON 27889929 27799841 27129731 26369696 25819719
25769779 26179878 26749953 27449971
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