MESOSCALE PRECIPITATION DISCUSSION 0550
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
413 AM EDT SUN OCT 04 2015

AREAS AFFECTED…NORTHEAST GA…SC…SOUTHEAST NC

CONCERNING…HEAVY RAINFALL…FLASH FLOODING LIKELY

VALID 040813Z – 041413Z

SUMMARY…HISTORIC RAINFALL EVENT CONTINUES ACROSS MUCH OF SOUTH
CAROLINA THIS MORNING WITH VERY HEAVY RAINFALL RATES EXPECTED.
WIDESPREAD AND SERIOUS FLASH FLOODING IS LIKELY TO REMAIN A
PROBLEM THROUGH 10 AM.

DISCUSSION…A HUGE MOISTURE PLUME FEEDING INTO THE NORTH SIDE OF
THE CLOSED UPPER LEVEL LOW OVER THE SOUTHEAST U.S. HAS MOVED VERY
LITTLE OVER THE PAST SEVERAL HOURS. TREMENDOUS MID AND UPPER
LEVEL DIVERGENCE WITHIN THIS PLUME IS ALLOWING FOR VIGOROUS ASCENT
IN AN ENVIRONMENT WITH 1.8 TO 2.3 INCH PW VALUES. SOME OF THIS
MOISTURE IS ORIGINATING FROM HURRICANE JOAQUIN. MUCAPE VALUES OF
1000-2000 J/KG NEAR THE SC COAST ARE HELPING TO FURTHER ENHANCE
RAINFALL RATES. A COASTAL FRONT NEAR THE SC/NC COAST REMAINS
NEARLY STATIONARY AND IS ACTING AS THE FOCUS FOR CONVECTION WITH
THE HIGHEST RAINFALL RATES. THE AXIS OF HEAVIEST PRECIPITATION
MAY PIVOT TOWARDS SOUTHEAST NORTH CAROLINA BORDER BY MID MORNING.

HI RES GUIDANCE INDICATES THAT LOCAL AMOUNTS OF 3-6″ ARE POSSIBLE
WITHIN THIS REGION OVER THE NEXT SIX HOURS, AND COULD FALL AT
RATES OF UP TO THREE INCHES PER HOUR AT TIMES. THESE TYPES OF
RAINFALL RATES ARE LIKELY TO CREATE SIGNIFICANT PROBLEMS IN URBAN
AREAS SUCH AS CHARLESTON, GREENVILLE/SPARTANBURG, COLUMBIA, AND
AUGUSTA. RADAR ESTIMATES HAVE BEEN RUNNING ABOUT 30 TO 50% TOO
LOW OVER THIS REGION OWING TO EFFICIENT RAINFALL PRODUCTION IN A
HIGH PW ENVIRONMENT. THE GROUND IS COMPLETELY SATURATED ACROSS
NORTHEAST GA AND MOST OF SC WHERE RAINFALL OVERNIGHT HAS BEEN
PERSISTENT. CONSIDERING THE RAINFALL EXPECTED, COMBINED WITH WHAT
HAS ALREADY FALLEN, MAJOR TO LOCALIZED CATASTROPHIC FLASH FLOODING
ALONG WITH POSSIBLE LANDSLIDES AND MUDSLIDES IN THE HIGHER
ELEVATIONS OF SC AND GA REMAIN AN ONGOING CONCERN.

HAMRICK