MESOSCALE PRECIPITATION DISCUSSION 0096
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1028 AM EDT SUN MAY 17 2015
 
AREAS AFFECTED...SOUTHEAST TX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 171425Z - 171900Z
 
SUMMARY...HEAVY SHOWERS AND THUNDERSTORMS WILL ARRIVE OVER THE
NEXT COUPLE OF HOURS AND WILL BE ACCOMPANIED BY LOCALLY INTENSE
RAINFALL RATES. GIVEN THE WET ANTECEDENT CONDITIONS...FLASH
FLOODING IS POSSIBLE.

DISCUSSION...THE LATEST IR SAT IMAGERY OVERALL SHOWS A TENDENCY
FOR CLOUD TOPS TO WARM ACROSS PORTIONS OF SOUTH AND SOUTHEAST TX
INVOLVING THE SOUTHERN END OF THE MORNING QLCS. HOWEVER...THE
CONVECTION ALONG A LINE FROM JUST EAST OF KBAZ SOUTHWEST TO JUST
NORTHEAST OF KCOT HAS BEEN QUITE INTENSE THE LAST COUPLE OF HOURS.
THE LATEST GOES-OTD ALGORITHM IS STILL SHOWING A FEW OVERSHOOTING
TOPS...AND THERE HAS BEEN A STRONG CONCENTRATION OF LIGHTNING AS
PER THE EXPERIMENTAL LIGHTNING DENSITY PRODUCT. THIS SUGGESTS
VIGOROUS UPDRAFTS/ASCENT WHICH APPEARS TO BE CONNECTED TO A
FAVORABLY DIVERGENT FLOW PATTERN ALOFT AS SEEN IN LATEST
WV/GOES-RGB AIRMASS IMAGERY.

THE LATEST HRRR STRONGLY SUGGESTS A WEAKENING TREND TO THIS
ACTIVITY AS IT ADVANCES TOWARD THE TX COAST...HOWEVER THE AIR MASS
AHEAD OF THE CONVECTIVE LINE IS MODERATELY UNSTABLE AND IS
CHARACTERIZED BY SURFACE DEWPOINTS IN THE MID 70S. BASED ON
THERMODYNAMICS ALONE...THERE IS A REASONABLE EXPECTATION THAT THE
SOUTHERN PORTION OF THE CONVECTIVE LINE WILL MAINTAIN ITSELF...AND
FOSTER VERY INTENSE RAINFALL RATES AND ESPECIALLY WITH SOME
ADDITIONAL OVERSHOOTING TOP ACTIVITY EXPECTED. AREAS FARTHER NORTH
AND EAST WILL SEE THE CONVECTION BE MORE DISORGANIZED BY
COMPARISON...ESPECIALLY NORTH OF KHOU.

REGARDLESS...THE FLASH FLOOD THREAT OVER THE NEXT FEW HOURS TO
SOUTHEAST TX IS HEAVILY CONNECTED TO RECENT RAINFALL WHICH HAS
LEFT THE GROUND SATURATED IN MANY AREAS. THE APPROACHING
CONVECTION SHOULD PRODUCE ADDITIONAL RAINFALL LOCALLY OF 2 TO 3
INCHES WHICH IS EXPECTED TO EXACERBATE RUNOFF CONCERNS.

ORRISON

ATTN...WFO...CRP...EWX...FWD...HGX...LCH...SHV...

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

LAT...LON   32039443 31169387 29979421 29069506 28469623 
            28269747 28229863 28329936 28639953 28859883 
            29399780 30399645 31879570