MESOSCALE PRECIPITATION DISCUSSION 0032
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1039 PM EST THU FEB 22 2018

AREAS AFFECTED...AR...ERN TX...NW LA...SE OK

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

VALID 230338Z - 230838Z

SUMMARY...THE POSSIBILITY OF HIGH-END AND POTENTIALLY
LIFE-THREATENING FLASH FLOODING WAS INCREASING OVER CENTRAL AND
SOUTHERN ARKANSAS. A TREND TOWARD A GREATER THREAT TO NORTHWEST
LOUISIANA WAS ALSO SEEN IN OBSERVATIONAL DATA AND HRRR FORECASTS.

DISCUSSION...THE LATEST WAVE OF HEAVY RAINFALL APPEARED TO BE
RAMPING UP AT 0315Z OVER PARTS OF TX/LA/AR. GOES-16 WATER VAPOR
AND INFRARED CHANNELS BEGAN TO SHOW AN INFLECTION POINT / SLIGHT
LEAF STRUCTURE UPSTREAM OVER WEST TEXAS...WHILE LOW LEVEL MOISTURE
TRANSPORT WAS ALREADY SUPPORTING ORGANIZED THUNDERSTORMS NORTH OF
A WARM FRONT IN LA/AR. OTHER TAIL-END STORMS IN FAR EASTERN TEXAS
APPEARED TO EVEN BE FEELING THE WARM SECTOR INFLOW VERY NEAR THE
SURFACE LOW PRESSURE CENTER...WITH SLOWER AND DEVIANT CELL MOTION
NOTED.

TRENDS ARE CONCERNING. MODELS GENERALLY AGREE TO TWO AXES OF
ORGANIZED CONVECTION THROUGH 10Z...ONE VERY NEAR THE FRONT
CROSSING NW LA...AND ANOTHER AS A CONTINUATION OF THE ACTIVITY
NORTH OF THE FRONT IN ARKANSAS...WITH POTENTIAL EXTENSION BACK
INTO NORTHEAST TEXAS / I-20 AND I-30 AS THE UPSTREAM WAVE YIELDS A
REORGANIZATION OF CONVERGENCE THROUGH THE DEPTH OF THE LOW LEVELS
BACK TO THE COOL SIDE OF THE FRONT. THE HRRR WAS GENERALLY
HANDLING THINGS THE BEST OF ANY MODEL THIS EVENING FROM TEXAS TO
KENTUCKY...AND 00-02Z RUNS SHOWED A DISTINCT TREND TOWARD HEAVIER
AMOUNTS IN THIS REGION...ESPECIALLY NORTHWEST LA. THE LINE ONGOING
NEAR PINE BLUFF / LITTLE ROCK AT 0315Z IS ALSO LIKELY TO BE
SUSTAINED.

MODEL FORECASTS OF 1 TO 2 INCHES ADDITIONAL RAINFALL MAY BE
UNDERDONE...AS BOTH KLCH AND KSHV EVENING SOUNDINGS SAMPLED
MODERATELY UNSTABLE LOW LEVELS WITH LITTLE OR NO INHIBITION / BORN
OUT BY ABSENCE OF INHIBITION PER SPC MIXED LAYER CAPE
MESOANALYSIS. THE SHREVEPORT SAMPLING OF 1.72 INCH PW / ALTHOUGH
WITH SOME CONVECTIVE CONTAMINATION / WOULD BE A FEBRUARY RECORD
FOR THE SITE. THUS...ADDITIONAL RAINFALL COULD TOP 2.5 OR 3.0
INCHES THROUGH MORNING...AND MUCH OF THIS AREA WAS ALREADY
EXPERIENCING FLOOD IMPACTS...WHICH WILL CERTAINLY BE MADE
WORSE...POTENTIALLY LIFE THREATENING...BY THE ADDITIONAL RAINFALL.

BURKE

ATTN...WFO...FWD...HGX...JAN...LCH...LZK...MEG...SHV...

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

LAT...LON   35849218 35849099 35209062 34549086 32409280
            30999425 30839437 30809496 31989460 32539473
            32319528 32239582 32689609 33799492