MESOSCALE PRECIPITATION DISCUSSION 0099
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
425 AM EDT TUE APR 04 2017

AREAS AFFECTED...NORTHEAST FL...EXT SOUTHEAST GA

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

VALID 040830Z - 041330Z

SUMMARY...PESKY REGENERATING CONVECTIVE COMPLEX ACROSS N FL
EXPECTED TO EXPAND INTO NE FL POSSIBLY AFFECTING THE I-10 CORRIDOR
AND JACKSONVILLE PROPER WITH HVY RAINS AND POSSIBLE FLASH FLOODING
CONDITIONS.

DISCUSSION...08Z SFC ANALYSIS DENOTES SFC BOUNDARY FROM NORTHERN
TIP OF APALACHEE BAY ACROSS TO JUST NORTH OF THE GA/FL BORDER AT
THE ATLANTIC COAST...SOUTHERLY COMPONENT SFC WIND FLOW INTERSECTS
WITH THE BOUNDARY PROVIDING STRONG SFC MST CONVERGENCE THOUGH
STRONGER FLOW WITHOUT FRICTIONAL EFFECTS OF 20-25KT ACROSS
APALACHEE BAY INTO THE BOUNDARY ALONG WITH CONFLUENT 40-45KT 850MB
FLOW CONTINUE TO MAINTAIN STRONG CONVECTION.  IN THE MID-LEVELS A
SUBTLE FLAT WAVE HAS BEEN TRACKING ACROSS S CENT GA ATTM PROVIDING
A BIT OF INCREASED UPPER LEVEL EVACUATION/ASCENT TO STRENGTHEN
UPDRAFTS.  GIVEN THE SFC FLOW IS HIGHLY RICH WITH MID 70S TDS AND
OVERALL TPWS OVER 1.75" CONVECTION HAS BEEN QUITE EFFICIENT WITH
RATES 2-2.5"/HR.  WHILE GREATER RAINFALL UP TO 8-9" FELL UPSTREAM
OVER RURAL/SWAMPY AREAS...RECENT UPTICK ALONG SOUTHERN-MOST
CONVERGENCE BAND AND FLAT WAVE BEGINNING TO EXIT COMPLEX SHOULD
START TO CROSS EASTERN I-10 TRACKING INTO JACKSONVILLE PROPER
WHERE URBAN CONDITIONS WILL POSE A GREATER FLASH FLOODING THREAT.

GIVEN THE SUBTLE NATURE OF THE WAVE/CONVERGENCE HI-RES GUIDANCE
HAS BEEN STRUGGLING THROUGH THE NIGHT TRYING TO HANDLE EACH
INCREASE OF CONVECTION WITH NO AVAIL...THOUGH RECENT HRRR AND RAP
RUNS HAVE BEEN LATCHING ONTO THE STRETCHING OF THE COMPLEX FURTHER
EAST TOWARD JACKSONVILLE PROVIDING SOME CONFIDENCE.  GIVEN
ORIENTATION OF THE BOUNDARY IS LIKELY NOT TO SHIFT MUCH AND
ONSHORE FLOW/LOW LEVEL CONVERGENCE SHOULD BE MAINTAINED THROUGH
PRE-DAWN CONVECTIVE MAXIMA...EXPECTATION OF 2-3" TOTALS ARE LIKELY
WITH ISOLATED 4-5" POSSIBLE...THOUGH WITH HIGH GUIDANCE VALUES. 
GIVEN THIS UNCERTAINTY AND PROLONGED DRY CONDITIONS ONLY CAN
SUGGEST FLASH FLOODING IS POSSIBLE AT THIS TIME.   

GALLINA

ATTN...WFO...JAX...TAE...

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

LAT...LON   30828145 29888129 29628295 29578341 29928371
            30158392 30568275