MESOSCALE PRECIPITATION DISCUSSION 0039
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1145 AM EST SAT FEB 24 2018

AREAS AFFECTED...NORTHEAST TX...EASTERN OK...CENTRAL/NORTHERN
AR...SOUTHERN MO...NORTHWEST TN...SOUTHERN IL...SOUTHWEST
IN...WESTERN KY

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

VALID 241645Z - 242245Z

SUMMARY...SHOWERS AND THUNDERSTORMS WILL CONTINUE TO EXPAND IN
COVERAGE OVER THE NEXT SEVERAL HOURS AND PROMOTE MORE CONCENTRATED
AREAS OF HEAVY RAINFALL. FLASH FLOODING IS LIKELY CONSIDERING THE
SATURATED SOIL CONDITIONS.

DISCUSSION...THE LATEST MRMS RADAR IMAGERY IS SHOWING A BROAD AND
EXPANDING AREA OF HEAVY SHOWERS AND THUNDERSTORMS ACROSS AREAS OF
NORTH-CENTRAL TO NORTHEAST TX AND EXTENDING UP ACROSS EASTERN OK
AND INTO WESTERN AR. THE CONVECTION CONTINUES TO BE AIDED BY THE
NOSE OF A 40 TO 50 KT SOUTHWEST LOW LEVEL JET WHICH IS FOSTERING
ROBUST WARM AIR ADVECTION AND ENHANCED MOISTURE TRANSPORT AHEAD OF
A LEAD SHORTWAVE TROUGH OVER EASTERN OK...AND ALSO A MUCH STRONGER
LARGE SCALE TROUGH NOW ENTERING THE CENTRAL/SOUTHERN HIGH PLAINS.

THE MOISTURE TRANSPORT IS RATHER IMPRESSIVE AS SEEN IN BLENDED-TPW
AND CIRA-LPW DATA SETS WHICH DEPICT A DEEPER LAYER CONNECTION FROM
THE EASTERN TROPICAL PACIFIC AND UP ACROSS MEXICO AND THE BROADER
SOUTHERN PLAINS AND LOWER MS VALLEY REGION. THE STRONGER LOW TO
MID LEVEL SOUTHWEST FLOW AHEAD OF THE UPSTREAM HEIGHT FALLS
CONTINUES TO OVERRUN A STABLE BOUNDARY LAYER FOCUSED NORTH OF WARM
FRONT ATTEMPTING TO LIFT UP ACROSS THE LOWER MS VALLEY. THERE IS A
LARGE AREA OF ELEVATED INSTABILITY WITH 500 TO 1000 J/KG OF MUCAPE
NOTED NORTH OF THE WARM FRONT OVER THE LOWER MS VALLEY AND BACK
TOWARD THE RED RIVER VALLEY. THIS HAS BEEN FACILITATING STRONGER
CONVECTIVE ORGANIZATION AND EXPANSION AND THE GOES-16 1-MINUTE IR
SATELLITE IMAGERY HAS BEEN OCCASIONALLY SHOWING A FEW OVERSHOOTING
TOP...MAINLY OVER SOUTH-CENTRAL TO SOUTHEAST OK WHICH HAS BEEN
ENHANCING RAINFALL RATES TO OVER 1 INCH/HR RECENTLY.

THE 12Z CAM GUIDANCE COLLECTIVELY AGREES IN A STRONG SURGE OF WARM
AIR/MOISTURE ADVECTION LIFTING UP ACROSS THE LOWER MS AND LOWER OH
VALLEYS THROUGH MID-AFTERNOON WITH A RATHER STRONG LOW LEVEL JET.
THIS COUPLED WITH STRONGER LOW LEVEL CONVERGENCE NEAR THE
FRONT...UPPER LEVEL DIVERGENCE AHEAD OF THE MAIN UPSTREAM
TROUGH...AND INCREASING INSTABILITY/SHEAR PROFILES...SHOULD DRIVE
A SW/NE EXPANSION OF CONVECTION WITH INCREASINGLY CONCENTRATED
AREAS OF HEAVY RAINFALL OVER THE NEXT SEVERAL HOURS.

RAINFALL RATES OF UP TO 2 INCHES/HR WILL BE POSSIBLE GIVEN THE
STRONGER CONVECTIVE ORGANIZATION...EFFICIENT MOISTURE TRANSPORT
AND INSTABILITY. THIS COUPLED WITH AT LEAST A PERIODICALLY
FAVORABLE CELL-TRAINING ENVIRONMENT OWING TO NEAR UNIDIRECTIONAL
LOW/MID LEVEL FLOW WILL FAVOR SOME ENHANCED RAINFALL TOTALS OF AS
MUCH AS 2 TO 4 INCHES THROUGH LATE-AFTERNOON WITH ISOLATED HEAVIER
AMOUNTS NOT OUT OF THE QUESTION.

GIVEN THE VERY WET ANTECEDENT CONDITIONS...THE EXPECTATION IS THAT
THESE RAINFALL AMOUNTS WILL BE CAPABLE OF PRODUCING ENHANCED AND
POTENTIALLY SIGNIFICANT RUNOFF PROBLEMS AND FLASH FLOODING. WILL
CONTINUE TO MONITOR WITH ADDITIONAL MPDS LIKELY NEEDED LATER TODAY
AND THIS EVENING.

ORRISON

ATTN...WFO...FWD...ILX...IND...LMK...LSX...LZK...MEG...OHX...
OUN...PAH...SGF...SHV...TSA...

ATTN...RFC...ABRFC...LMRFC...MBRFC...NCRFC...OHRFC...WGRFC...

LAT...LON   38678803 38578703 38288626 37568628 37038690
            36328791 35568942 35208998 34609120 33999230
            33399358 32779495 32549600 32839675 33569669
            34129629 35389512 36279460 36809426 37389327
            38009161 38458982