MESOSCALE PRECIPITATION DISCUSSION 0049
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
602 PM EDT FRI APR 24 2015
 
AREAS AFFECTED...NRN TEXAS INTO THE ARKLATEX 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 242201Z - 250300Z
 
SUMMARY...RAINFALL RATES OF 2-3 INCHES IN 3 HOURS ARE EXPECTED TO
INCREASE THE THREAT FOR FLASH FLOODING BETWEEN 00-03Z FROM NRN
TEXAS INTO AND ACROSS THE ARKLATEX. ANTECEDENT RAINFALL ACROSS THE
REGION HAS LOWERED FLASH FLOOD GUIDANCE.

DISCUSSION...RECENT RADAR TRENDS SHOWED AN INCREASE IN CONVECTIVE
COVERAGE AHEAD OF A DRYLINE EXTENDING SSWD FROM NEAR CDS TO JUST
PAST 6R6...AND NEAR AN OUTFLOW BOUNDARY LOCATED JUST SOUTH OF THE
DFW METROPLEX. THESE STORMS ARE OCCURRING OUT AHEAD OF AN EJECTING
SHORTWAVE CURRENTLY PUSHING THROUGH WRN OKLAHOMA WITHIN AN
ENVIRONMENT OF AMPLE INSTABILITY ESTIMATED TO BE BETWEEN 1000 AND
3000 J/KG. NORTH OF A STATIONARY FRONT...SPECIAL 21Z SOUNDING FROM
SHV INDICATED ABOUT 900 J/KG MU CAPE WITH A PRECIPITABLE WATER
VALUE OF 1.57 INCHES WHICH WOULD BE HIGHER IF NOT FOR A SHALLOW
POCKET OF DRY AIR NEAR 850 MB. SURROUNDING GPS PW VALUES TO THE
WEST AND EAST ARE CLOSER TO 1.7 INCHES...NEAR A DAILY
CLIMATOLOGICAL MAX FOR LATE APRIL AT SHV.

AS THE SHORTWAVE CONTINUES TO TRACK EWD BEYOND 00Z...850-700 MB
FLOW IS EXPECTED TO SLIGHTLY INCREASE FROM CURRENT VALUES OF 40
KTS FROM THE SW...PARALLELING THE CLOUD BEARING MEAN FLOW OF
SIMILAR MAGNITUDE ALLOWING FOR PERIODS OF TRAINING CONVECTION. AS
A WHOLE...CLUSTERS OF CONVECTION ARE EXPECTED TO PROGRESS ENEWD
AHEAD OF THE QUICKLY ADVANCING SHORTWAVE...BUT CONSISTENT RUNS OF
THE HRRR AND ESRL EXPERIMENTAL HRRR...WHICH ARE HANDLING ONGOING
CONVECTION THE BEST THIS AFTERNOON...INDICATE THE POTENTIAL FOR 3
HRLY RAINFALL RATES EXCEEDING FLASH FLOOD GUIDANCE ACROSS NRN
TEXAS INTO THE ARKLATEX. GIVEN EARLIER RAINFALL DURING THE DAY
TODAY...THESE FFG VALUES ARE LOWER THAN TYPICALLY OBSERVED WHICH
INCREASES THE FLASH FLOOD RISK.

OTTO

ATTN...WFO...FWD...LZK...OUN...SHV...TSA...

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

LAT...LON   34229541 33929256 32699309 32269607 32759744 
            33849719