Graphic for MPD #0023

MESOSCALE PRECIPITATION DISCUSSION 0023
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1115 AM EST WED FEB 21 2018

AREAS AFFECTED...SERN TX INTO W-CNTRL AND NRN LA

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 211543Z - 212115Z

SUMMARY...AN AXIS OF TRAINING HEAVY RAIN WITH RAINFALL RATES OF
1.5 TO 2.5 IN/HR...ORIENTED FROM SERN TX INTO CNTRL/NRN LA MAY
CAUSE FLASH FLOODING. ADDITIONAL RAINFALL OF 3 TO 5 INCHES WILL BE
POSSIBLE.

DISCUSSION...OVER THE PAST HOUR...AN AXIS OF HEAVY RAIN...WITH
KPOE DUAL-POL ESTIMATED RAINFALL RATES OF 2 TO 3 IN/HR...HAS BEEN
OBSERVED OVER JASPER AND NEWTON COUNTIES THROUGH 15Z IN FAR ERN TX
WITH SUPERCELL STRUCTURES OBSERVED FARTHER NORTHEAST INTO PORTIONS
OF WRN LA. EARLIER NEARBY OBSERVATIONS IN THE AREA SHOWED SIMILAR
RAINFALL RATES TO THE DUAL-POL ESTIMATES ALTHOUGH SOME HAIL
CONTAMINATION MAY SUPPORT ACTUAL OBSERVED RATES SLIGHTLY LOWER
THAN THE DUAL-POL ESTIMATES...PERHAPS 1.5 TO 2.5 IN/HR OVER
JASPER/NEWTON COUNTIES. LOW LEVEL INFLOW WAS CONFLUENT INTO A SLOW
MOVING FRONT...EXTENDING SWWD THROUGH NRN MS/LA INTO A SURFACE LOW
SOUTH OF SHV...WITH THE COLD FRONT CONTINUING SWWD INTO S-CNTRL TX
AT 15Z. PRECIPITABLE WATER VALUES CONTINUE TO BE NEAR FEBRUARY
RECORD VALUES AT SHV FOR 12Z AND AREA-WIDE VALUES ARE 200 TO 300
PERCENT OF NORMAL.

OBSERVED AND SHORT-TERM FORECASTS OF PROPAGATION VECTORS SHOW
MOVEMENT TOWARD THE NORTHEAST AT 10-20 KT...ROUGHLY PARALLEL TO
THE FRONTAL BOUNDARY. THE ONGOING LOCATION OF HEAVIEST RAIN RATES
ALONG THE SABINE RIVER VALLEY SEEMS TO BE CO-LOCATED WITH THE NRN
GRADIENT OF MLCAPE AS SEEN ON THE SPC MESOANALYSIS PAGE FOR 15Z.

DIFFLUENT FLOW ALOFT CONTINUES TO SUPPORT EVACUATION...BENEATH THE
LOW LEVEL CONVERGENCE NEAR THE SURFACE BOUNDARY. GIVEN ONLY SLOW
FORECAST MOVEMENT OF THE FRONTAL BOUNDARY TO THE SOUTH AND LITTLE
CHANGE TO THE JET PATTERN IN THE UPPER LEVELS...THE EXPECTATION IS
FOR TRAINING TO CONTINUE WHILE SLOWLY EXPANDING DOWNSTREAM INTO
NRN LA OVER THE NEXT 2-4 HOURS. FLASH FLOODING WILL BE POSSIBLE
WITHIN AXES OF TRAINING WHICH COULD SUPPORT AN ADDITIONAL 3 TO 5
INCHES OF RAIN THROUGH 21Z.

OTTO

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

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

LAT...LON   33519169 33379111 33019094 32599099 31489215
            30479281 30039367 30069485 30699495 31669459
            32919340


Last Updated: 1115 AM EST WED FEB 21 2018