MESOSCALE PRECIPITATION DISCUSSION 0143
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1149 PM EDT THU JUN 19 2014
 
AREAS AFFECTED...FAR S TX...SW TX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 200349Z - 200649Z
 
SUMMARY...A SHORT TERM FLASH FLOOD RISK EXISTS AT LEAST THROUGH
07Z...AND POSSIBLY BEYOND IF CONVECTION CAN REMAIN ORGANIZED
AROUND A SMALL CIRCULATION NEAR UVALDE.

DISCUSSION...AT 0330Z ONGOING THUNDERSTORMS WERE TIED TO A
MESOSCALE VORTEX NEARING UVALDE TX. CONVECTION FARTHER SOUTH HAD
BEEN ENHANCED BY THE AFTERNOON SEA BREEZE...AND IS LESS LIKELY TO
PERSIST INTO THE NIGHT. A NUMBER OF FORECAST MODELS INDICATE HEAVY
RAIN IN THIS REGION OVERNIGHT...BUT SIMULATED REFLECTIVITY FROM
THE HIRES MODELS SUGGESTS LOOSE ORGANIZATION...AND EVENTUAL
MIGRATION NORTHWESTWARD. THE HRRR HAD CAPTURED THE VERY ORGANIZED
NATURE OF THE EVENT IN MEXICO LAST NIGHT...BUT THE MCV TONIGHT MAY
BE TOO SMALL SCALE FOR THE MODEL.

IN THE NEAR TERM...KDFX REFLECTIVITY WAS SUFFERING SOME
ATTENUATION GIVEN HEAVY RAIN AT THE DOME...BUT DID INDICATE A
MARKED INCREASE OF CONVERGENCE ON THE SOUTHEAST FLANK OF THE MCV
PER VELOCITY DATA. THE CONCERN IS THAT ENHANCED LOW LEVEL INFLOW
WILL SUSTAIN CONVECTION THAT OTHERWISE HAS LITTLE SYNOPTIC
SUPPORT...AND THAT...SIMILAR TO LAST NIGHT IN MEXICO...THE NAM/GFS
FORECAST BACKWARD PROPAGATING CORFIDI VECTORS TO BECOME DIRECTLY
OPPOSED TO MEAN CELL MOTIONS...FROM THE NW VERSUS SE...WHILE
FORWARD PROPAGATION DROPS TO NEAR ZERO. SMALL SCALE BUT INTENSE
RAINFALL IN THE 2-3 INCH/HR RANGE COULD OCCUR AT THE MCV IN THIS
SCENARIO. IN A WORST CASE...WITH LITTLE MOVEMENT THIS PROCESS
COULD PRODUCE A VERY LARGE AMOUNT OF RAIN LOCALLY.

WITH TIME...SYNOPTIC LIFT AND 850 MB THETA-E TRANSPORT WILL
DEVELOP NORTHWESTWARD...AND THE MODELS INITIATE ADDITIONAL AREAS
OF HEAVY RAIN. THE MORE FOCUSED FLASH FLOOD RISK...HOWEVER...IS
NEAR THE ORIGINAL MCV OR ANY SUBSEQUENT ONES THAT WOULD TAKE TIME
TO GROW. 

BURKE

ATTN...WFO...CRP...EWX...SJT...MAF...

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

LAT...LON   27659946 27919906 28869887 30089935 30519997 30760104
            30820230 30260256 29880174 29230084 28260008 27659946