MESOSCALE PRECIPITATION DISCUSSION 0041
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
530 PM EST SAT FEB 24 2018

AREAS AFFECTED...FAR NORTHEAST TX...NORTHWEST LA...CENTRAL/EASTERN
AR...NORTHWEST MS...CENTRAL/WESTERN TN

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 242230Z - 250400Z

SUMMARY...A STRONG LINE OF INTENSE SHOWERS AND THUNDERSTORMS
CONTINUES TO ADVANCE EAST ACROSS THE LOWER MS VALLEY WITH HEAVY
RAINS FALLING ON SATURATED GROUND AND RESULTING IN FLASH FLOODING.

DISCUSSION...THE LATEST MRMS RADAR IMAGERY IS SHOWING AN EXTENSIVE
BAND OF INTENSE SHOWERS AND THUNDERSTORMS ASSOCIATED WITH A SQUALL
LINE WHICH EXTENDS FROM SOUTHEAST MO SOUTHWEST ACROSS CENTRAL AR
AND DOWN INTO EXTREME NORTHEAST TX. RAINFALL RATES OF AS MUCH AS 1
TO 1.5 INCHES/HR ARE NOTED AS THE BAND OF STRONG CONVECTION MOVES
EAST AHEAD OF AN APPROACHING COLD FRONT FROM THE WEST.

THE CONVECTION OVER THE NEXT SEVERAL HOURS SHOULD CONTINUE TO
ADVANCE EAST AND BE RELATIVELY PROGRESSIVE...BUT ALSO BE
SUSTAINABLE GIVEN A ROBUST 50 TO 60 KT+ LOW LEVEL JET OUT AHEAD OF
IT...WELL-DEFINED LARGE SCALE ASCENT AHEAD OF AN UPPER TROUGH
CROSSING THE CENTRAL PLAINS...AND A POOL OF AT LEAST MODEST
INSTABILITY.

THE MOISTURE TRANSPORT IS VERY IMPRESSIVE GIVEN THE STRENGTH OF
THE LOW LEVEL JET...WITH RESULTING 850 MB MOISTURE FLUX ANOMALIES
OF 3 TO 5 SIGMAS ABOVE NORMAL ACROSS THE REGION. THIS WILL
MAINTAIN HIGHLY EFFICIENT RAINFALL PRODUCTION WITHIN THE
CONVECTIVE LINE. PWATS OVERALL ARE ON THE ORDER OF 1.5 TO 1.75
INCHES AND ARE CONTRIBUTING TO THE ENHANCED RAIN RATES.

THE SOUTHWEST FLANK OF THE CONVECTION INVOLVING FAR NORTHEAST
TX...ADJACENT AREAS OF FAR NORTHWEST LA AND INTO SOUTHERN AR MAY
BECOME SOMEWHAT MORE PROBLEMATIC COMPARED TO THE REST OF THE
CONVECTIVE LINE...AS THIS SOUTHWEST FLANK OF CONVECTION IS
ORIENTED A LITTLE MORE PARALLEL TO THE DEEP LAYER MEAN FLOW.
CONSEQUENTLY...THERE IS A CONCERN AT LEAST INTO THE EARLY EVENING
HOURS FOR SOME PERIODIC TRAINING OF CONVECTIVE CELLS THAT WILL
ENHANCE RAINFALL TOTALS.

IN GENERAL...AN ADDITIONAL 1 TO 3 INCHES OF RAIN IS
EXPECTED...WITH THE HEAVIER TOTALS MOST LIKELY ACROSS THE
SOUTHWEST PORTION OF THE MPD AREA WHERE SOME ISOLATED HEAVIER
AMOUNTS TO OVER 4 INCHES ARE POSSIBLE THROUGH THE EVENING BEFORE
ENDING. THESE AMOUNTS AREA-WIDE ARE EXPECTED TO RESULT IN FLASH
FLOODING GIVEN THE INTENSE SHORT-TERM RAIN RATES AND WET
ANTECEDENT CONDITIONS.

ORRISON

ATTN...WFO...HUN...JAN...LMK...LZK...MEG...OHX...PAH...SHV...

ATTN...RFC...ABRFC...LMRFC...OHRFC...SERFC...WGRFC...

LAT...LON   37078554 37028504 36618568 36048661 35258777
            34328918 33389104 32759249 32359372 32329442
            32499490 32999485 33629406 34159334 34819278
            35219251 35829178 36199133 36469064 36448986
            36458894 36598763 36678690