Flash Flood Guidance
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000
AWUS01 KWNH 230052
FFGMPD
TXZ000-OKZ000-230600-

MESOSCALE PRECIPITATION DISCUSSION 0715
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
851 PM EDT TUE AUG 22 2017

AREAS AFFECTED...NORTH TX THROUGH SOUTHWEST OK INTO EASTERN OK

CONCERNING...HEAVY RAINFALL

VALID 230100Z - 230600Z

SUMMARY...SLOW MOVING CONVECTION TAPS INSTABILITY AND DEEP
MOISTURE TO PRODUCE A FLASH FLOOD THREAT THROUGH THE LATE EVENING
HOURS.

DISCUSSION...REGIONAL RADARS INDICATED THAT THE CONVECTION OVER
THE TX PANHANDLE HAS BECOME MORE OUTFLOW DOMINATED...DROPPED INTO
NORTH TX...AND BECOME MORE DISORGANIZED. FURTHER NORTHEAST...
CONVECTION IS FIRING OVER PORTIONS OF CENTRAL AND EASTERN
OK...WHERE THE AIRMASS HAS NOT BEEN OVERTURNED BY EARLIER
CONVECTION. THE NEW CONVECTION IS FORMING IN AN AXIS OF 2000-25000
J/KG OF MLCAPE... WHICH IS COINCIDENT WITH A RIBBON OF 2.00 INCH
PRECIPITABLE WATER.

WEAKLY DIFLUENT FLOW AHEAD OF A WEAK SHORT WAVE OVER EASTERN NM IS
PROVIDING AN AREA OF SYNOPTIC SCALE ASCENT FOR THE CONVECTIVE
DEVELOPMENT. HOWEVER...THE 850-300 MB MEAN WIND REMAINS FAIRLY
WEAK HERE (WITH WIND VECTORS OF 10 KNOTS OR LESS)...SO THE
CONVECTIVE CELL MOTIONS HAVE BEEN RELATIVELY SLOW. HOURLY RAINFALL
RATES FROM THE KTLX RADAR WERE AS HIGH AS 2.50 INCHES...BUT BASED
ON THE HCA PRODUCT... THESE AMOUNTS COULD BE HAIL CONTAMINATED.

THE FRONTAL BOUNDARY IS EXPECTED TO MOVE LITTLE OVER PORTIONS OF
CENTRAL AND EASTERN OK...AND IT IS EXPECTED TO REMAIN A FOCUS FOR
INSTABILITY AND DEEP MOISTURE TO FOSTER A FLASH FLOOD THREAT. CELL
MERGERS DUE TO SLOW CELL MOTIONS...AS WELL AS SHORT TERM
TRAINING...POSE THE GREATEST THREAT FOR FLASH FLOODING THROUGH
LATE EVENING.

THE MOST RECENT HRRR SHOWED SCATTERED 4.00+ INCH RAINFALL AMOUNTS
ALONG THE BOUNDARY EXTENDING FROM FAR NORTH TX INTO FAR EASTERN
OK. GIVEN THE SLOW CELL MOTIONS AND DEEP MOISTURE IN PLACE...THESE
AMOUNTS COULD SERVE AS LOCAL CONVECTIVE MAXIMA WITH THE SLOWER
MOVING STORMS.

FURTHER SOUTH INTO NORTH TX...THE CONVECTION SHOULD REMAIN
UNORGANIZED AND TIED MAINLY TO OUTFLOW BOUNDARIES. HOWEVER...LOCAL
2.00+ INCH RAINFALL AMOUNTS ARE POSSIBLE HERE AS WELL...WHICH
COULD SUPPORT A FLASH FLOOD THREAT THROUGH 05Z.

HAYES

...PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...AMA...FWD...LUB...MAF...OUN...SJT...TSA...

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

LAT...LON   36189700 35609485 33129847 32619954 32530055
            32950177 34380150



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