MESOSCALE PRECIPITATION DISCUSSION 0703
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
226 PM EDT SUN SEP 25 2016
 
AREAS AFFECTED...NORTHEAST AND CENTRAL TX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 251830Z - 252230Z
 
SUMMARY...CONVECTION FORMING IN AN AREA OF LOW LEVEL CONVERGENCE
WILL TRAIN IN A HIGH MOISTURE CONTENT AIRMASS...RESULTING IN A
FLASH FLOOD THREAT THROUGH THIS AFTERNOON.

DISCUSSION...CONVECTIVE COVERAGE IS INCREASING ACROSS PORTIONS OF
NORTHEAST TX EARLY THIS AFTERNOON...AS LOW LEVEL CONVERGENCE
FOCUSES MOISTURE AND INCREASING INSTABILITY ALONG A SURFACE
TROUGH. THE CONVECTION IS FIRING IN AN AREA OF 1000-1500 J/KG
MLCAPE (AS THE LAST OF THE LOW LEVEL CIN IS ERASED)...WHICH HAS
BECOME COINCIDENT WITH A RIBBON OF 2.00+ INCH PRECIPITABLE WATER
AIR. THE IR LOOP SHOWS STEADILY COOLING TOPS...AND THE KFWS RADAR
IS ALREADY INDICATING BETWEEN 1.50 AND 2.00 INCHES OVER SECTIONS
OF MCLENNAN...LIMESTONE AND SOUTHERN NAVARRO COUNTIES. 

THE CONVECTION IS ALSO EMBEDDED IN A UNIDIRECTIONAL FLOW
PATTERN...WHICH HAS BEEN WEAKENING THIS MORNING. THE
UNIDIRECTIONAL FLOW OVER THE LOW LEVEL CONVERGENCE SHOULD HELP THE
CONVECTION FORM ONE OR MORE TRAINING BANDS. THE CONVECTIVE BANDS
SHOULD CONTINUE TO MOVE SLOWLY EASTWARD AHEAD OF THE MID LEVEL
SYSTEM OVER NORTHERN MEXICO...WHILE THE CELLS IN THE BANDS TRACK
NORTH...SLOWING WITH TIME. THE TRAINING AND SLOWING CELLS INCREASE
THE POTENTIAL FOR FLASH FLOODING ALONG THE LOW LEVEL CONVERGENCE
ZONE THROUGH THE AFTERNOON HOURS.

WHILE MUCH OF THE HIGH RESOLUTION GUIDANCE IS NOT CAPTURING THE
DEVELOPING CONVECTION WELL AT THIS POINT...THE 12Z WRF ARW SEEMS
TO HAVE SOME IDEA (THOUGH IT IS SLOW WITH THE DEVELOPMENT)
CONCERNING THE EVOLUTION OF THE EVENT. BASED ON THIS
SOLUTION...AND THE TRENDS ON RADAR...LOCAL 2-3 INCH RAINFALL
AMOUNTS ARE POSSIBLE...ESPECIALLY WERE TRAINING PERSISTS. THREE
HOUR FLASH FLOOD GUIDANCE VALUES ARE FAIRLY HIGH...SO TRAINING IS
NECESSARY FOR THE CONVECTIVE TO PRESENT A BONAFIDE FLASH FLOOD
THREAT.

HAYES

ATTN...WFO...EWX...FWD...HGX...OUN...SHV...TSA...

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

LAT...LON   34559676 34339592 33339551 31869541 30929543 
            30569553 30359566 30159591 29949631 29759703 
            29829717 29939744 30129765 31239787 32029772 
            32509760 33319745 34309692