MESOSCALE PRECIPITATION DISCUSSION 0455
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1121 AM EDT SUN JUL 15 2018

AREAS AFFECTED...SOUTH-CENTRAL KY...CENTRAL TN...NORTH-CENTRAL AL

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

VALID 151520Z - 151900Z

SUMMARY...ADDITIONAL CLUSTERS OF SHOWERS AND THUNDERSTORMS WILL
LIKELY RESULT IN FLASH FLOODING CONCERNS OVER THE NEXT SEVERAL
HOURS...AND ESPECIALLY OVER AREAS THAT SAW EARLIER HEAVY RAINFALL.

DISCUSSION...THE LATEST GOES-16 CLEAN IR SATELLITE IMAGERY SHOWS
MULTIPLE COLD-TOPPED CONVECTIVE CLUSTERS DROPPING SOUTHEAST ACROSS
SOUTH-CENTRAL KY AND THROUGH CENTRAL TN. ADDITIONAL SMALL SCALE
AREAS OF CONVECTION ARE NOTED ALSO DOWN ACROSS NORTH-CENTRAL AL.

THE AREA OF GREATEST CONCERN OVER THE NEXT FEW HOURS WILL TEND TO
BE CENTRAL TN WHERE HEAVY RAINFALL OF AS MUCH AS 2 INCHES EARLIER
THIS MORNING HAS LOCALLY SATURATED THE GROUND. GIVEN THE
ADDITIONAL CONVECTIVE DEVELOPMENT NOTED UPSTREAM NEAR THE KY/TN
BORDER THAT IS DROPPING SOUTHEAST...THERE WILL LIKELY BE A CONCERN
FOR FLASH FLOODING GIVEN THE WET ANTECEDENT CONDITIONS AT THIS
POINT.

THE CONVECTION HAS BEEN TENDING TO FORM OUT AHEAD OF A WEAK
WSW/ENE ORIENTED SHEAR AXIS OVER THE LOWER OH VALLEY...AND WITH
PROXIMITY TO VERY MODEST 250 MB RIGHT-ENTRANCE REGION JET
DYNAMICS. THE AIRMASS OVER THE REGION IS EXTREMELY MOIST AND IS
MODERATELY UNSTABLE. IN FACT...THE 12Z KBNA RAOB DEPICTED A PW OF
2.27 AND A K-INDEX OF 46. THE LATEST RAP ANALYSIS SHOWS A NOSE OF
MLCAPE VALUES TO NEAR 1500 J/KG UP ACROSS CENTRAL TN.

THE CONVECTION ACROSS THE REGION WILL BE HIGHLY EFFICIENT GIVEN
THE WARM LAYER DEPTH AND DEGREE OF MOISTURE UP IN THE 500/300 MB
LAYER. EXPECT RAINFALL RATES TO BE AS MUCH AS 2.5 INCHES/HR WITH
THE ONGOING CONVECTION...AND ESPECIALLY WITH THE ACTIVITY DROPPING
SOUTHEAST FROM SOUTH-CENTRAL KY.

EXPECT ADDITIONAL RAINFALL AMOUNTS OF AS MUCH AS 3 TO 4 INCHES TO
BE POSSIBLE THROUGH 18Z...AND ADDITIONAL CONVECTION WILL LIKELY
DEVELOP BEYOND THIS TIME FRAME WHICH WILL CONTINUE THE FLASH FLOOD
THREAT. WILL CONTINUE TO CLOSELY MONITOR.

ORRISON

ATTN...WFO...HUN...LMK...MRX...OHX...PAH...

ATTN...RFC...LMRFC...OHRFC...

LAT...LON   36798654 36728599 36568567 36228538 35758543
            35238580 34888626 34418668 34358710 34468726
            35058724 35478721 35928730 36308757 36588756
            36758718