431
AWUS01 KWNH 260417
FFGMPD
TXZ000-260920-
MESOSCALE PRECIPITATION DISCUSSION 1251
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1117 PM EST TUE NOV 25 2025
AREAS AFFECTED...SOUTH TEXAS
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 260415Z - 260920Z
SUMMARY...A LOCALIZED FLASH FLOOD RISK WILL EXIST ACROSS PORTIONS
OF SOUTHERN TX THROUGH AT LEAST 09Z. SLOW MOVING AND/OR
BACKBUILDING OF THUNDERSTORMS COULD RESULT IN ISOLATED TOTALS IN
EXCESS OF 3-5 INCHES, THOUGH SOME UNCERTAINTY IN PLACEMENT AND
TIMING REMAIN.
DISCUSSION...04Z RADAR AND INFRARED SATELLITE IMAGERY SHOWED A
LONE THUNDERSTORM OVER SOUTHERN WEBB COUNTY, ABOUT 15 MILES EAST
OF THE RIO GRANDE WITH A SLOW NORTHWARD DRIFT. RADAR AND SATELLITE
IMAGERY ALSO SHOWED RECENT ATTEMPTS AT DEVELOPMENT OVER LIVE OAK
COUNTY AND PORTIONS OF NORTHERN MEXICO THOUGH LOW LEVEL CIN MAY BE
HINDERING FURTHER DEVELOPMENT. MRMS-DERIVED HOURLY RAINFALL WAS
OVER 2 INCHES WITH THE CELL ALTHOUGH THE LIKELY PRESENCE OF LARGE
HAIL MAY BE OVER-INFLATING THOSE VALUES AND NO GROUND TRUTH WAS
AVAILABLE TO CONFIRM ACTUAL RAIN RATES. THE CELL WAS LOCATED NEAR
A QUASI-STATIONARY FRONT WHICH HAS DRIFTED NORTH AND WEST OVER THE
PAST COUPLE OF HOURS DUE TO A WEAK LOW LEVEL EASTERLY SURGE OFF OF
THE WARM GULF WATERS WITH SURFACE DEWPOINTS IN THE LOWER 70S FROM
CRP TO BKS AND SOUTHWARD TO THE RIO GRANDE. LOW LEVEL CONVERGENCE
AND LIFT AUGMENTED BY A SUBTLE SHORTWAVE IMPULSE TRACKING EAST
FROM NORTH-CENTRAL MEXICO AS SEEN IN 6.2 MICRON IMAGERY SEEM TO BE
TRIGGERS FOR THE STORM(S).
00Z SOUNDINGS FROM CRP AND BRO SHOWED 1.3 TO 1.6 INCH PW VALUES
ALONG WITH 1500-2000 J/KG MLCAPE, WITH THIS AIRMASS LIKELY IN
PLACE NEAR THE CELL OVER WEBB COUNTY. THE ENVIRONMENT WAS
SUPPORTIVE OF A MIXTURE OF STORM MODES WITH SUFFICIENT SHEAR FOR
ORGANIZED CELLS AND STRAIGHT-LINE HODOGRAPHS WHICH COULD SUPPORT
SPLITTING STORMS. BUNKERS RIGHT MOTION WAS TOWARD THE SSE NEAR 20
KT, BUNKERS LEFT FROM THE SSW NEAR 15 KT AND DEEPER LAYER MEAN
WINDS FROM THE WEST BETWEEN 5 AND 20 KT.
WHILE RECENT HIRES MODEL GUIDANCE SHOWS A DECENT SIGNAL FOR
LOCALIZED HEAVY RAIN IN THE VICINITY OF SOUTHERN TX, THERE IS POOR
AGREEMENT IN PLACEMENT AND TIMING. CURRENT THINKING IS FOR THE
EXISTING CELL OVER WEBB COUNTY TO MAINTAIN FOR AT LEAST ANOTHER
1-2 HOURS WITH A CONTINUED DRIFT TOWARD THE NORTH OR WEST WITH
LOCALIZED HEAVY RAIN. THE FUTURE BEYOND THAT TIME IS UNCLEAR AS
BETTER LOW LEVEL CONFLUENCE SHIFTS WESTWARD INTO MEXICO BUT
ADDITIONAL CONVECTIVE DEVELOPMENT APPEARS POSSIBLE NEAR THE
FRONTAL BOUNDARY AND SOUTH TX COAST LATER IN THE NIGHT. ADDITIONAL
POTENTIAL FOR HIGH RATES IN EXCESS OF 2 IN/HR AND SPOTTY TOTALS IN
EXCESS OF 3 TO 5 INCHES WILL REMAIN POSSIBLE.
OTTO
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...BRO...CRP...EWX...
ATTN...RFC...FWR...NWC...
LAT...LON 28739716 28419661 27979657 27069704 25679698
25829839 26089916 26689958 27359974 27970016
28239969 28689774
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