MESOSCALE PRECIPITATION DISCUSSION 0297
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
353 PM EDT SUN JUN 04 2017

AREAS AFFECTED...SOUTHEAST TX

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 042000Z - 050000Z

SUMMARY...SLOW MOVING HIGHLY EFFICIENT LINE OF CONVECTION MAY POSE
SHORT-TERM FLASH FLOOD THREAT PARTICULARLY IN URBAN
CORRIDOR/HOUSTON METROPLEX

DISCUSSION...GOES-EAST WV LOOP DENOTES A WEAK TWIST OVER
SOUTH-CENTRAL TX NEAR BAZ SHIFTING EAST.  AHEAD OF IT MODEST
DIFFLUENCE ALOFT FROM 5H AND ABOVE SUPPORTS BROAD SCALE ASCENT TO
SUPPORT LOWER LEVEL CONVERGENCE ALLOWING FOR CONVECTIVE GROWTH AND
MAINTENANCE OVER THE NEXT FEW HOURS.  THE MCS THAT LEAD TO FF
ALONG THE UPPER TX/W LA COAST THIS MORNING HAS KICKED AN OUTFLOW
WEST THROUGH THE HOUSTON METRO DENOTED IN HGX REFLECTIVITY...THIS
IS AN ADDED ELEMENT OF LOWER LEVEL CONVERGENCE WITH A NARROW AXIS
OF ENHANCED INSTABILITY WHERE CLEAR SKIES THIS MORNING (NOT
AFFECTED BY MCS CIRRUS SHIELD) SUPPORTED MID TO UPPER 80F TEMPS
INCREASING MLCAPES FROM 1500-2500 J/KG (TOWARD THE COAST). 
SURFACE TDS IN THE LOW TO MID-70S AND FAIRLY SATURATED MID-LEVELS
SUPPORT TPWS TO 2.0".  AS SUCH PARAMETERS SUPPORT CONVECTION
CAPABLE OF 2"/HR RAIN RATES.  LOW LEVEL FLUX IS NOT TOO STRONG TO
SUPPORT INCREASED RATES THOUGH ALSO ALLOWS FOR NEAR ZERO
PROPAGATION VECTORS PER THE RECENT RAP AND WITH CLOUD BARING MEAN
WINDS OF 10-15KTS IN A DIFFLUENT REGIME.  

CURRENT RADAR DENOTES THE OUTFLOW AS WELL AS THE MID-LEVEL TROF
FORCING LINE ARE WELL ESTABLISHED AND LIKELY TO MERGE OVER THE
NEXT HOUR IN PROXIMITY TO THE HOUSTON METRO WHERE FLASH FLOODING
WILL BE MORE LIKELY.  AS SUCH RAIN TOTALS OF 2-4" ARE POSSIBLE
WITH SOME HI-RES CAMS SUGGESTING AS MUCH AS 5" WHICH MAY NOT BE
FULLY RULED OUT GIVEN SLOW MOTIONS/RAINFALL EFFICIENCY AND
MERGERS. TOWARD 23-00Z THE COMPLEX WILL MOVE THROUGH HOUSTON
TOWARD SE TX AND WILL LIKELY REDUCE IN INTENSITY DUE TO STABILIZED
ENVIRONMENT WITH LITTLE/NO RECHARGE FROM SOLAR INSOLATION AT PEAK
HEATING. 

GALLINA

ATTN...WFO...CRP...HGX...

ATTN...RFC...WGRFC...

LAT...LON   31259531 30829485 29859475 29119493 28649554
            28319613 28179663 28249701 28469723 28799711
            29099678 29239652 29469636 29769631 30239628
            30679620 31039577