Graphic for MPD #0187

MESOSCALE PRECIPITATION DISCUSSION 0187
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
456 PM EDT THU MAY 04 2017

AREAS AFFECTED...SOUTHERN APPALACHIANS/BLUE RIDGE MOUNTAINS

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

VALID 042055Z - 050255Z

SUMMARY...SHOWERS AND THUNDERSTORMS HAVE BEGUN TO DEVELOP IN THE
PIEDMONT, WHICH ARE MOVING INTO RUGGED TOPOGRAPHY WITH PARTIALLY
SATURATED SOILS.  WITH HOURLY RAIN RATES UP TO 1" AND LOCAL
AMOUNTS OF 2-3" POSSIBLE, FLOODING IS POSSIBLE.

DISCUSSION...THE MESOSCALE ANALYSIS IS COMPLEX IN THE REGION, WITH
A WEAK MESOSCALE WAVE IN SOUTHEAST GA, WHICH HAS BOTH A STATIONARY
FRONT IN TOW ACROSS SOUTHERN SC AND A COASTAL FRONT OVER THE TOP
OF THE FEATURE MOVING INTO THE WESTERN CAROLINAS, WHICH IS
BEGINNING TO ACT AS A FOCUS FOR SHOWERS AND THUNDERSTORMS. 
MUCAPES IN THE AREA ARE 100-300 J/KG, WITH A SUBTLE RISING TREND
ACROSS WESTERN NC AND SOUTH-CENTRAL VA OVER THE PAST COUPLE HOURS.
 INFLOW AT 850 HPA IS CONVERGENT WITHIN A CYCLONIC FLOW REGIME AT
35-40 KTS PER VAD WIND PROFILES IN THE AREA.  PRECIPITABLE WATER
VALUES ARE RISING, CURRENTLY NEAR 1.25".

THE EXPECTATION IS FOR THE INSTABILITY TO RISE SOMEWHAT FURTHER
OVER THE NEXT SEVERAL HOURS AS THE COASTAL FRONT MOVES INTO THE
TERRAIN, THOUGH THE BEST INSTABILITY REMAINS IN THE COASTAL PLAIN.
 INCREASING LOW-LEVEL INFLOW (TO 50+ KTS) IS EXPECTED TO RAISE
PRECIPITABLE WATER VALUES CLOSE TO 1.75" WITH TIME.  CONSIDERING
THE SLIGHTLY RISING INSTABILITY WITH TIME, HOURLY RAINFALL RATES
COULD REACH 1" LOCALLY.  THE MESOSCALE GUIDANCE SHOWS A SIGNAL FOR
LOCAL 2-3" AMOUNTS IN THIS AREA, WHICH WOULD SLIGHTLY EXCEED FLASH
FLOOD GUIDANCE VALUES.  SOILS SHOULD BE PARTIALLY SATURATED AS
THIS REGION HAS BEEN WET AS OF LATE, RECEIVING 150-400% OF THEIR
AVERAGE RAINFALL OVER THE PAST COUPLE WEEKS PER THE AHPS WEBSITE. 
THIS MAGNITUDE OF RAINFALL WOULD BE MORE OF AN ISSUE WITHIN RUGGED
TERRAIN AND OVER SATURATED SOILS.

ROTH

ATTN...WFO...FFC...GSP...LWX...MRX...RAH...RNK...

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

LAT...LON   38307854 38067841 36817953 35278141 34528308
            34418471 35128428 35768274 36428196 36588194
            37168152 37657975 38187892


Last Updated: 456 PM EDT THU MAY 04 2017