MESOSCALE PRECIPITATION DISCUSSION 0038
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
231 PM EDT SUN APR 12 2015
 
AREAS AFFECTED...CENTRAL/SOUTHERN GA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 121825Z - 122200Z
 
SUMMARY...VERY-SLOW MOVING SHOWERS AND THUNDERSTORMS WITH INTENSE
RAINFALL RATES WILL CONTINUE THIS AFTERNOON. SOME FLASH FLOODING
WILL BE POSSIBLE LOCALLY.

DISCUSSION...SURFACE OBSERVATIONS SHOW A FRONT ORIENTED W/E ACROSS
SOUTH-CENTRAL GA EARLY THIS AFTERNOON THAT IS ATTEMPTING TO LIFT
BACK NORTH. THERE IS A FAIRLY SIGNIFICANT AMOUNT OF MOISTURE
POOLED ALONG THE BOUNDARY...AND THE LATEST RADAR IMAGERY SHOWS A
CLUSTER OF ALREADY VERY SLOW-MOVING SHOWERS AND THUNDERSTORMS.

GPS-DERIVED PWATS OVER SOUTH-CENTRAL GA ARE ABOUT 1.6 TO 1.7
INCHES AND THE LATEST RAP ANALYSIS SHOWS THE CONVECTION TAKING
ADVANTAGE OF A WELL-DEFINED INSTABILITY GRADIENT ACROSS THE REGION
WITH SBCAPE VALUES PUSHING 1500 TO 2000 J/KG NOW ACROSS FAR
SOUTHERN GA. THE RADAR IMAGERY SUGGESTS THERE IS A FAIRLY SHALLOW
AND WEAK VORT CENTER INTERACTING WITH THE FRONT OVER THE REGION
AND THIS COUPLED WITH THE INSTABILITY TRANSPORT INTO THE BOUNDARY
SEEMS TO BE DRIVING THE CONVECTION.

HI RES MODELS SUGGEST HEAVY RAINS THIS AFTERNOON ACROSS THIS
REGION...WITH THE 12Z NAM-CONEST...12Z WRF-ARW AND 12Z WRF-NMMB
ALL FAVORING POCKETS OF 2 TO 4 INCHES OF RAIN WITH ISOLATED
HEAVIER AMOUNTS. GIVEN THE RELATIVELY SHALLOW NATURE OF THE
CONVECTION WHICH WILL FOSTER EFFICIENT RAINFALL PROCESSES...AND
WEAK STEERING FLOW...IT IS POSSIBLE THAT LOCALLY VERY HEAVY TOTALS
COULD MATERIALIZE THAT COULD EXCEED 5 INCHES. FFG VALUES ARE
HIGH...BUT RAINFALL RATES ARE EXPECTED TO BE VERY INTENSE AND THIS
MAY RESULT IN FLASH FLOODING.

ORRISON

ATTN...WFO...CHS...FFC...JAX...TAE...

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

LAT...LON   33328411 32988313 32408249 31688182 31088177 
            30698231 30808316 31098360 31488411 31938443 
            32678485 33178473