Graphic for MPD #0760

MESOSCALE PRECIPITATION DISCUSSION 0760
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
207 PM EDT TUE AUG 29 2017

AREAS AFFECTED...SOUTHEAST LA...SOUTHERN MS...SOUTHERN AL...FL
PANHANDLE

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

VALID 291805Z - 300005Z

SUMMARY...BANDS OF HEAVY SHOWERS AND THUNDERSTORMS WILL BE
ADVANCING NORTH THROUGH THE AFTERNOON IN OFF THE GULF OF MEXICO.
FLASH FLOODING IS LIKELY GIVEN THE EXTREMELY HEAVY RAINFALL RATES
THAT ARE EXPECTED.

DISCUSSION...RADAR IMAGERY IS SHOWING AN AXIS OF HEAVY RAINFALL
STRETCHING FROM SOUTHEAST LA AND AREAS OF SOUTHERN MS EASTWARD
ACROSS FAR SOUTHERN AL AND APPROACHING THE FL PANHANDLE. THE
CONVECTION IS DEVELOPING NEAR AND JUST NORTH OF A STATIONARY FRONT
DRAPED ACROSS A LARGE AREA OF THE GULF COAST. INCREASING SOUTH TO
SOUTHWEST FLOW ASSOCIATED WITH A DEEP LAYER WARM CONVEYOR BELT
WELL EAST OF THE CENTER OF T.S. HARVEY IS GREATLY ENHANCING THE
ISENTROPIC ASCENT ACROSS THE REGION. MEANWHILE...STRONGER SURFACE
CONVERGENCE/LOW LEVEL FORCING NEAR THE FRONT AND GREATER
MOISTURE/INSTABILITY TRANSPORT IS NOTED AS WELL.

CLOUD TOPS HAVE BEEN GENERALLY COOLING OVER THE LAST HOUR AS
LARGER SCALE FORCING INCREASES...AND THIS IS ESPECIALLY NOTED
ACROSS FAR SOUTHERN AL AND AREAS JUST OFFSHORE OF THE WESTERN FL
PANHANDLE WHERE VERY HEAVY RAINFALL IS ABOUT TO ARRIVE IN OFF THE
GULF OF MEXICO. PWATS ARE ALREADY HIGHLY REFLECTIVE OF A DEEP
TROPICAL AIRMASS WITH VALUES GENERALLY IN THE 2.25 TO 2.5 INCH AND
THIS WILL SUPPORT EXTREME RAINFALL RATES IN EXCESS OF 3 INCHES/HR
WITHIN THE STRONGER CONVECTIVE CORES.

THE LATEST HIRES MODEL CONSENSUS SUGGESTS SOME GRADUAL NORTHWARD
ADVANCE OF THE AFOREMENTIONED FRONTAL ZONE. THIS SHOULD HELP ALLOW
SOME OF THE STRONGER CONVECTIVE ELEMENTS AND RESULTING HEAVY
RAINFALL TO LIFT A BUT FARTHER NORTH THROUGH THE AFTERNOON HOURS
WHICH WILL ENCAPSULATE MORE AREAS OF ESPECIALLY SOUTHERN AL AND
THE FL PANHANDLE.

MEANWHILE...THERE ARE SOME SIGNALS THAT CONVECTIVE BANDING COULD
BECOME BETTER ORGANIZED/CONCENTRATED OVER AREAS OF FAR SOUTHEAST
LA AND SOUTHERN MS WHICH WOULD GRADUALLY MOVE BACK INTO FAR
SOUTHERN AL LATER THIS AFTERNOON OR EARLY THIS EVENING. RECENT
HRRR/HRRRX GUIDANCE ALONG WITH HRRR-TLE AND 12Z ARW DATA WERE
SUGGESTING THIS. OVERALL...EXPECT THROUGH 00Z ADDITIONAL RAINFALL
TOTALS OF GENERALLY 3 TO 6 INCHES...WITH ISOLATED HEAVIER TOTALS
THAT COULD APPROACH 8+ INCHES OVER FAR SOUTHERN MS AND FAR
SOUTHERN AL AS SUGGESTED BY THE 15Z HRRR-TLE. FLASH FLOODING IS
LIKELY ACROSS THESE AREAS GIVEN THE OVERALL SET-UP AND CONCERN FOR
SUCH INTENSE SHORT-TERM RAINFALL RATES.

ORRISON

ATTN...WFO...BMX...JAN...LIX...MOB...TAE...

ATTN...RFC...LMRFC...SERFC...

LAT...LON   32208768 32138676 31868586 31008489 30338441
            29668456 29558510 29838557 30168629 30128718
            30108789 30018857 29808926 29488985 29359046
            29739102 30599089 31349024 31818959 32108880
           


Last Updated: 207 PM EDT TUE AUG 29 2017