359
AWUS01 KWNH 102142
FFGMPD
TXZ000-110200-
MESOSCALE PRECIPITATION DISCUSSION 0088
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
541 PM EDT FRI APR 10 2026
AREAS AFFECTED...SOUTHEAST TEXAS INCLUDING THE HOUSTON
METROPOLITAN AREA
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 102141Z - 110200Z
SUMMARY...SLOW-MOVING, OUTFLOW-DRIVEN THUNDERSTORMS INTERACTING
OVER HIGHLY URBANIZED AREAS WILL BE CAPABLE OF PRODUCING LOCALIZED
RAINFALL RATES OF 2+ INCHES/HOUR. ISOLATED TOTALS OF 3 TO 4 INCHES
MAY RAPIDLY OVERWHELM MUNICIPAL DRAINAGE, MAKING LOCALIZED FLASH
FLOODING POSSIBLE.
DISCUSSION...RECENT RADAR AND SATELLITE TRENDS DEPICT SCATTERED,
SLOW-MOVING CLUSTERS OF THUNDERSTORMS DEVELOPING ACROSS SOUTHEAST
TEXAS. THE THERMODYNAMIC ENVIRONMENT IS CHARACTERIZED BY A MOIST,
WEAKLY CONVERGENT LOW-LEVEL FLOW OFF THE GULF OF AMERICA, WITH
PWATS NEAR 1.75 INCHES AND MLCAPE VALUES AROUND 1500 J/KG. WHILE
DEEP-LAYER SHEAR REMAINS WEAK (EFFECTIVE BULK SHEAR 20-30 KTS),
WEAK UPPER-LEVEL DIVERGENCE IS SUPPLYING MODEST DEEP-LAYER ASCENT,
AIDING IN SOME MAINTENANCE OF ROBUST, HIGH-EFFICIENCY UPDRAFTS.
GIVEN THE WEAK STEERING FLOW, THE CONVECTIVE MODE IS PRIMARILY
PULSE-TYPE AND OUTFLOW-DOMINANT. THE IMMEDIATE FLASH FLOOD THREAT
WILL BE DRIVEN BY MESOSCALE BOUNDARY INTERACTIONS. REGIONAL RADAR
CURRENTLY SHOWS MULTIPLE OUTFLOW BOUNDARIES IN PLAY?MOST NOTABLY
ONE POSITIONED SOUTHWEST OF THE HOUSTON METRO AND ANOTHER NEAR
IAH. AS THESE BOUNDARIES INTERACT OVER THE NEXT FEW HOURS,
MECHANICAL LIFT MAY FORCE RAPID, NEAR-STATIONARY CONVECTIVE
DEVELOPMENT AND UPSCALE GROWTH DIRECTLY OVER MORE SENSITIVE URBAN
LOCATIONS.
RAINFALL RATES HAVE ALREADY APPROACHED 2 INCHES/HOUR WITH THE
STRONGEST CELLS. HIGH-RESOLUTION GUIDANCE, PARTICULARLY THE HRRR
WHICH HAS INITIALIZED THE CURRENT CONVECTIVE EVOLUTION WELL,
SUGGESTS THESE BOUNDARY COLLISIONS WILL SUPPORT ISOLATED
ADDITIONAL RAINFALL TOTALS OF 3 TO 4 INCHES THROUGH EARLY THIS
EVENING. FURTHERMORE, THE 12Z HREF HIGHLIGHTS 10-30% PROBABILITIES
FOR 3-HOUR FFG EXCEEDANCE THIS OVER THE NEXT SEVERAL HOURS. GIVEN
THE HIGH IMPERVIOUS SURFACE COVERAGE ACROSS THE HOUSTON METRO,
THESE RATES AND ACCUMULATIONS MAY OVERWHELM LOCAL DRAINAGE SYSTEMS
AND BAYOUS, LEADING TO ISOLATED AREAS OF RAPID-ONSET URBAN FLASH
FLOODING.
ORRISON
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...EWX...FWD...HGX...
ATTN...RFC...FWR...NWC...
LAT...LON 31059623 30659519 30319469 29999457 29479462
28919531 28909635 29599753 30359774 30939727
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