MESOSCALE PRECIPITATION DISCUSSION 0112
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
930 PM EDT SAT APR 21 2018
AREAS AFFECTED...SOUTHEAST TEXAS
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 220130Z - 220630Z
SUMMARY...POTENTIAL FOR TRAINING CELLS WITH RAIN RATES UP TO 2"/HR
AND POSSIBLE FLASH FLOODING
DISCUSSION...RECENT GOES-16 VISIBLE/3.9 SWIR/10.3 IR AND WSR-88D
RALA MOSAIC DEPICT INCREASED CONVECTION ACTIVATING ALONG COASTAL
BOUNDARY GENERALLY COLLOCATED WITH DEEP MOISTURE AXIS OF SSW TO
NNE WARM CONVEYOR BELT THAT EXTENDS FROM DEEP SOUTH TEXAS TO THE
ARKLATEX REGION. RADAR AND SURFACE OBSERVATIONS ALSO DENOTE A
WEAK SFC INFLECTION ALONG THE LINE MOVING INTO LAVACA COUNTY,TX.
NORTH AND EAST OF THIS INFLECTION...LOW LEVEL MOISTURE FLUX AND
CONVERGENCE WERE MAXIMIZED WITH ABOUT 1000 J/KG OF SBCAPES AIDING
DEVELOPMENT. ADDITIONALLY THE AREA IS ALSO FAVORABLE ALOFT WHERE
GOES-16 WV SUITE SHOW THE APEX OF THE ANTICYLONIC SUBTROPICAL JET
CLOUD STREAKS WITH 3-4H LOWER FLOW BACKING TOWARD THE NORTHEAST
PROVIDING A LOCALIZED MAXIMA OF DIVERGENCE TO FURTHER STRENGTHEN
UPDRAFTS.
SFC TDS UP TO 70F AND 10-15 KTS AND MODESTLY DEEP SATURATION
(1.75" TPW) IN THE PROFILES (PER CIRA LAYERED PW SUITE) IN THE
WARM CONVEYOR SUPPORT GOOD FLUX BUT ALSO EFFICIENT RAINFALL
PRODUCTION. THIS IS REFLECTED WELL WITH RECENT 01Z HRLY
OBSERVATION OF 1.99". LIMITING FACTORS ARE IN PLACE MAINLY
FOCUSED ON DRY/ABSORPTIVE SOILS CONDITIONS WITH 1HR FFG VALUES
OVER 3 AND 3HRLY OVER 4" MAKING FLASH FLOODING LIMITED TO VERY
ISOLATED AREAS OF MAXIMIZED TRAINING AND URBAN/HYDROPHOBIC
SURFACES. MEAN CELL MOTIONS WITHIN THE WARM SECTOR (SE OF THE
WARM CONVEYOR) ARE FLATTER RELATIVE TO THE INFLECTION POINT
SUGGESTING TRAINING IS POSSIBLE. RECENT HRRR SUGGESTS 3-4" ARE
POSSIBLE BUT OVER A SMALL DOMAIN. AS SUCH FLASH FLOODING IS
CONSIDERED POSSIBLE BUT ONLY BARELY ABOVE THRESHOLD...SUGGESTING
VERY LIMITED AREAL CONCERN OR DURATION.
GALLINA
ATTN...WFO...EWX...HGX...LCH...SHV...
ATTN...RFC...WGRFC...
