MESOSCALE PRECIPITATION DISCUSSION 0131
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1123 AM EDT TUE APR 19 2016
 
AREAS AFFECTED...SOUTHEAST TX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 191521Z - 192121Z
 
SUMMARY...SCATTERED THUNDERSTORMS ARE EXPECTED TO FORM IN AN AREA
THAT RECEIVED HEAVY RAINFALL YESTERDAY ACROSS SOUTHEAST TX.  FLASH
FLOODING IS POSSIBLE WITHIN THIS SATURATED AREA.

DISCUSSION...A MESOANALYSIS FOR THE REGION DEPICTS A COUPLE WEAK
WAVES OF LOW PRESSURE ALONG A BAROCLINIC ZONE JUST OFF THE MIDDLE
AND LOWER TX COAST.  THE SURFACE FEATURES LIE EAST OF AN AREA OF
DARKENING ON WATER VAPOR IMAGERY MOVING ACROSS SOUTH-CENTRAL TX. 
OVER THE TOP OF THE NORTHERN WAVE, A MOISTURE GRADIENT HAS SET UP
IN THE FORM OF A COASTAL FRONT, SEPARATING GULF MOISTURE FROM
DRIER CONTINENTAL AIR.  PRECIPITABLE WATER VALUES OF 1.77" WERE
DERIVED VIA GPS AT GALVESTON TX WITH VALUES JUST ABOVE 1.6" IN
SOUTHWEST LA.  MLCAPES IN THE AREA ARE 500+ J/KG WHILE MUCAPES ARE
1000+ J/KG.  THE INFLOW AT 850 HPA IS 25 KTS FROM THE SOUTHWEST.

THE CAM GUIDANCE IS NEARLY UNANIMOUS IN IMPLYING THAT THE ZONE OF
MOISTURE GRADIENT WOULD BE THE FOCUS FOR CONVECTION ROUGHLY
BETWEEN 16-21Z.  RAP GUIDANCE HAS THE LOW-LEVEL INFLOW DECREASING
WITH TIME, IMPLYING THAT CELLS SHOULD BE OF A PULSE NATURE.  CELL
MOTION SHOULD BE NORTHEAST AT 10-15 KTS, MOVING ALONG WITH THE
850-400 HPA MEAN WIND.  SHOULD ORGANIZED ACTIVITY OCCUR, IT WOULD
PROPAGATE SLOWLY TO THE EAST-SOUTHEAST.  ANY CONVECTION IN THIS
REGION COULD STRENGTHEN THE TEMPERATURE DIFFERENTIAL ALONG THE
MOISTURE GRADIENT, MAKING IT A POTENTIALLY MORE IMPORTANT
CONVECTIVE BOUNDARY.  AVAILABLE MOISTURE IMPLIES HOURLY RAIN RATES
UP TO 2", WHILE CAM GUIDANCE INDICATES 3-5" IS POSSIBLE LOCALLY. 
WITHIN A SATURATED/FLOODED AREA, HEAVY RAINS COULD LEAD TO OR
RENEW FLASH FLOODING.

ROTH

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

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

LAT...LON   30659462 30629386 30369361 29749366 29499441 
            29109495 29049525 29529546 30099539 30499512