MESOSCALE PRECIPITATION DISCUSSION 0605
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
627 PM EDT FRI OCT 23 2015
 
AREAS AFFECTED...MUCH OF EAST TX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 232230Z - 240430Z
 
SUMMARY...FLASH FLOOD PRODUCING CONVECTION WILL TRAIN ALONG A LOW
LEVEL BOUNDARY AS IT MOVES SLOWLY NORTH DURING THE EVENING HOURS. 

DISCUSSION...CONVECTION CONTINUES TO DEVELOP AND TRACK ALONG A LOW
LEVEL BOUNDARY EXTENDING FROM CENTRAL INTO NORTHEAST TX LATE THIS
AFTERNOON. THE BOUNDARY IS SITTING IN AN AXIS OF 2.00 INCH
PRECIPITABLE WATER (WHICH IS ABOUT TWO STANDARD DEVIATIONS ABOVE
THE MEAN)...AND THE CONVECTION IS FORMING AND MOVING ON THE
NORTHERN EDGE OF THE BEST INSTABILITY. THE CONVECTION IS PRODUCING
HOURLY RAINFALL RATES BETWEEN 2.00 AND 2.50 INCHES (PER KFWS RADAR
AND MRMS RAINFALL RATE PRODUCT). 

THE CONVECTION IS EXPECTED TO FOLLOW THE LOW LEVEL BOUNDARY AS IT
MOVES SLOWLY NORTHWARD THIS EVENING...IN RESPONSE TO BUILDING MID
LEVEL HEIGHTS IN THE WESTERN GULF OF MEXICO. THE MID LEVEL FLOW
AND CORFIDI VECTORS REMAIN ALIGNED IN THE VICINITY OF THE LOW
LEVEL BOUNDARY...PROMOTING TRAINING AND MERGING CELLS. 

MOST OF THE HIGH RESOLUTION GUIDANCE (INCLUDING THE 20Z HRRR/RAP)
SHOWED LOCAL 3-5 INCH RAINFALL AMOUNTS ALONG THE BOUNDARY. GIVEN
RAINFALL RATES SEEN ON LOCAL RADARS DURING THIS AFTERNOON...THESE
AMOUNTS SEEM PLAUSIBLE. THE ADDITIONAL RAINFALL WILL RESULT IN
FLASH FLOODING...AND THE FLASH FLOODING COULD BE SIGNIFICANT IN
AREAS WHERE TRAINING PERSISTS.

FURTHER SOUTH...A BAND OF NORTH/SOUTH ORIENTED CONVECTION
CONTINUES TO STREAM NORTH ACROSS PORTIONS OF SOUTH TX. THE
CONVECTION IS FORMING IN AN AXIS OF 1500-2000 J/KG MLCAPE...AS
WELL AS 2.30-2.40 INCH PRECIPITABLE WATER AIR. THUS FAR...THE
CONVECTION HAS REMAINED WIDELY SCATTERED... AND HAS NOT POSED MUCH
OF A FLASH FLOOD THREAT. HOWEVER...THE 20Z HRRR/RAP...AS WELL AS
THE 12Z WRF-ARW/NMMB...SUGGEST THAT THE INFLOW BECOMES STRONGER
AND CONVECTION BECOMES MORE WIDESPREAD TOWARD 24/03Z. THE
INCREASED CONVECTIVE COVERAGE...IN A HIGH MOISTURE CONTENT
AIRMASS...WILL RESULT IN AN INCREASED THREAT FOR FLASH FLOODING
LATE THIS EVENING. 

HAYES

ATTN...WFO...BRO...CRP...EWX...FWD...HGX...SHV...SJT...

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

LAT...LON   33749614 33689482 32649430 30649662 28729753 
            27279776 28049864 28269872 28919880 30129889 
            30469916 30109965 29869989 29900068 30070138 
            30660145 32539908 33069812