MESOSCALE PRECIPITATION DISCUSSION 0043
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
952 AM EDT THU APR 16 2015
 
AREAS AFFECTED...EXTREME NORTHWEST GA...NORTHERN
AL...CENTRAL/EASTERN TN...SOUTHERN/EASTERN KY...EXTREME SOUTHWEST
VA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 161345Z - 161745Z
 
SUMMARY...SLOW-MOVING AND HEAVY SHOWERS AND THUNDERSTORMS FALLING
OVER WET ANTECEDENT SOIL THIS MORNING MAY RESULT IN SOME FLASH
FLOODING THROUGH MIDDAY.

DISCUSSION...THE LATEST IR/WV IMAGERY SHOWS A SHORTWAVE LIFTING
GRADUALLY NORTHEAST UP THROUGH THE LOWER OH VALLEY. CONVECTION IS
DEVELOPING IN A FEW FAIRLY DISORGANIZED CLUSTERS ACROSS NORTHERN
AL...CENTRAL TN AND INTO SOUTHERN KY.

THE ACTIVITY IS FORMING WITHIN THE NOSE OF A MODEST ELEVATED
INSTABILITY AXIS WHICH IS BEING AIDED BY A BROAD BUT FAIRLY WEAK
SOUTHWESTERLY WARM AIR ADVECTION PATTERN. THE CONVECTIVE TOPS ARE
STILL RELATIVELY WARM...BUT THE CONVECTION APPEARS TO BE TENDING
TO EXPAND IN COVERAGE SOMEWHAT GIVEN THE STRONGER DYNAMICS OF THE
SHORTWAVE.

THE MAIN CONCERN THROUGH MIDDAY WILL BE THE HEAVY RAINS FALLING ON
AREAS THAT ALREADY HAVE SATURATED OR NEALY SATURATED GROUND OWING
TO RECENT HEAVY RAINFALL. ISOLATED RAINFALL RATES ARE ALREADY
EXCEEDING 1 INCH/HR...AND THAT IS LIKELY TO EXCEED FLASH FLOOD
GUIDANCE VALUES AT LEAST LOCALLY...AND ESPECIALLY UP ACROSS
PORTIONS OF NORTHERN TN AND SOUTHERN KY.

THE LATEST HRRR GUIDANCE DOES NOT HAVE THE BEST HANDLE ON THE
CURRENT ACTIVITY...BUT IT DOES SUGGEST ADDITIONAL AMOUNTS OF UP TO
2 TO 3 INCHES LOCALLY THROUGH EARLY AFTERNOON. GIVEN THE WET
ANTECEDENT CONDITIONS AND RAINFALL RATES...SOME FLASH FLOODING
WILL BE POSSIBLE.

ORRISON

ATTN...WFO...BMX...FFC...HUN...JKL...LMK...MRX...OHX...

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

LAT...LON   37828457 37738343 36838293 35998340 34878466 
            34288596 34518738 35388760 36238720 36668687 
            37108619