MESOSCALE PRECIPITATION DISCUSSION 0611
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
154 AM EDT SUN OCT 25 2015
 
AREAS AFFECTED...SE TEXAS...SW LOUISIANA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 250553Z - 251153Z
 
SUMMARY...STRONG EXTREMELY MOIST ONSHORE FLOW LIFTING OVER COASTAL
FRONTAL BOUNDARY TO PERSIST WITH UP TO 1.25"/HR RATES TO PROLONG
INUNDATION FLOODING CONDITIONS. 

DISCUSSION...NEGATIVELY TILTED MID-LEVEL TROF FROM 5H CENTER OVER
CENTRAL TX AND 7H CENTER OF FORMER PATRICIA JUST SW OF HOUSTON
METRO.  HIGH LATENT HEAT RELEASE DEVELOPED A MCV AND REFLECTED
SURFACE LOW JUST EAST OF SOUTH PADRE ISLAND LIFTING NNE...WITH A
SECONDARY SURFACE WAVE JUST SE OF THE 7H LOW OFFSHORE.  CONTINUED
HEIGHT FALLS AND SURFACE PRESSURE FALLS WILL START TO CONSOLIDATE
THE SURFACE LOWS PIVOTING THEM VERY NEAR THE BRAZORIA COUNTY COAST
 WHILE INCREASING LOW LEVEL FLOW FROM 30 KTS TO 50 KTS AT 85H OUT
OF THE SOUTHEAST.  STRONG 25-30 KT SURFACE ONSHORE FLOW WILL
CONTINUE TO INCREASE FRONTOGENETIC FORCING AND LIFT OF EXTREMELY
SATURATED LOW LEVEL PROFILE WITH AMPLE TPWS OVER 2.5".  GIVEN THE
STRENGTH AND THE LIFT BUT NEGLIGIBLE INSTABILITY...INCREASED SLANT
OF THE ISENTROPIC SURFACE WILL STILL ALLOW FOR SLIGHTLY DEEPER
WARM RAINFALL GENERATION PROCESSES TO MAINTAIN WITH BROAD
.75-1.0"/HR RATES...TAPERING OFF A BIT IN THE WRAPPING BACK WARM
CONVEYOR BELT INTO MATAGORDA/JACKSON/WHARTON COUNTIES BY 12Z...YET
STRONG ENOUGH TO COMPOUND ONGOING INUNDATION FLOODING. ISOLATED
1.25-1.5" ONE-HOUR TOTALS ARE NOT OUT OF THE REALM OF
POSSIBILITY...WITH 6HR TOTALS LIKELY IN THE 2-4" RANGE WITH
ISOLATED 6" VALUES FROM FORT BEND/BRAZORIA TO THE ENE TO THE TX/LA
LINE LIKELY

EASTWARD SHIFT OF BROADENING SELY GULF FLOW WILL HELP TO EXPAND
EASTWARD EXTENT OF THESE MODERATE STRATIFORM RAINS INTO SW LA. 
FLOODING THREAT WOULD BE LIMITED TO COMPOUNDING INUNDATION
FLOODING AS WELL PARTICULARLY GIVEN THE STRONG ONSHORE
FLOW/COASTAL FLOODING CONDITIONS NOT ALLOWING OUTFLOW TO THE GULF. 

A SLIGHT CHANCE OF WEAK CONVECTIVE DEVELOPMENT WITH SOME 500-1000
J/KG INSTABILITY VERY NEAR THE SURFACE CYCLONE/WARM SECTOR MAY
PROGRESS NORTHWARD NEAR ENOUGH TO AFFECT COASTAL BEACHES BY 09-10Z
GIVEN CURRENT TRACKING BASED ON RADAR TRENDS...AS SUPPORTED BY THE
ESRL EXPERIMENTAL HRRR OR NAM-CONEST. HOWEVER...THIS IS LOOKING
LESS AN LESS FAVORABLE WITH MORE EASTERLY DRIFT OF SOUTHERN MCV
DRIVEN SURFACE LOW...AS SUPPORTED BY THE MOST RECENT HRRR...ARW
AND NSSL-WRF RUNS.   

GALLINA

ATTN...WFO...HGX...LCH...

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

LAT...LON   31029377 30679316 30329274 29749262 29659300 
            29579358 29349462 28949516 28619592 28849620 
            29489618 30449559 30819508 30989460