MESOSCALE PRECIPITATION DISCUSSION 0642
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
735 AM EDT MON AUG 07 2017

AREAS AFFECTED...SOUTH CENTRAL TX

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 071135Z - 071435Z

SUMMARY...MERGER OF COMPLEXES POSE VERY HIGH BURST OF RAINFALL
WITH CONTINUED SHOWERS POSING FLASH FLOODING RISK

DISCUSSION...EXPERIMENTAL GOES-16 10.3 IR SHOWS AN EXPLOSIVE
DEVELOPMENT OF GROWING COMPLEX OF VERY COLD CLOUD TOPS (AS LOW AS
-84C) THUNDERSTORMS OVER BANDARA AND MEDINA COUNTY OVER THE LAST
HOUR OR SO.  THIS IS IN RESPONSE TO INCREASED CONVERGENCE ALONG  A
MID-LEVEL BOUNDARY/EFFECTIVE COLD FRONT  MCV/SHORTWAVE LOCATED IN
THE THE SOUTHERN TX HILL COUNTRY WHERE LOW LEVEL FLOW HAD BACKED
IN RESPONSE TO ITS DEEPENING.

ADDITIONALLY...COLD POOL DRIVEN SQUALL LINE FROM CENTRAL TX
CONTINUES TO DRIVE SOUTH ON SOUTHERLY INFLOW...WITH THE WESTERN
EDGE OF THE LINE STALLING UNDER WEAKER FORWARD PROPAGTION (DUE TO
INFLUENCE OF SHORTWAVE TO ITS NORTHWEST) AND CURRENTLY
INTERSECTING/MERGING WITH THE NEW RAPID DEVELOPMENT.

STRONG MOISTURE FLUX AND AMPLE DEEP MOIST PROFILES SUPPORT TPWS
AOA 2.25" AND LIKELY TO SUPPORT RATES UP TO 3"/HR GIVEN THE
MERGERS.  THIS MERGER/INTERSECTION SHOULD EXHAUST THE LOCAL
INSTABILITY AND SUPPORT FURTHER SOUTHERN PROPAGATION OVER THE NEXT
TWO HOURS...BUT WITH THE INCREASE IN LATENT HEAT RELEASE...FURTHER
FOCUSING/DEVELOPMENT OF AN MCV/MESO LOW WILL ALLOW FOR MODERATE TO
HEAVY RAIN SHOWERS TO REMAIN IN THE VICINTIY WITH RATES UP TO
1"/HR FURTHER COMPOUNDING ANY FLOODING CONDITIONS.  AS SUCH
LOCALIZED TOTALS TO 2-3" ARE LIKELY WITH POSSIBLE 4 OR 5" HIGHLY
LOCALIZED MAXIMA POSSIBLE.

OF GREATER CONCERN...IS ANY EASTWARD SHIFT OF THE MID-LEVEL
EFFECTIVE COLD FRONT OF THE DEVELOPING MCV (WHICH GIVEN TRENDS
APPEARS LIKELY) WILL POSE A THREAT TO METRO SAN ANTONIO INCREASING
THE LIKELIHOOD FOR FLASH FLOODING CONDTIONS KNOWNING TO THE PRONE
AREA/URBAN SETTING.  AS SUCH FLASH FLOODING IS CONSIDERED LIKELY. 

GALLINA

ATTN...WFO...CRP...EWX...

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

LAT...LON   30139935 30109796 29909740 29319746 28689815
            28369912 28809955 29239951 29789970