MESOSCALE PRECIPITATION DISCUSSION 0542
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
354 PM EDT FRI OCT 02 2015
 
AREAS AFFECTED...E SOUTH CAROLINA...S/CENT NORTH CAROLINA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY 
 
VALID 021953Z - 030153Z
 
SUMMARY...DEEPER CONVECTIVE GROWTH WITH INCREASED RAINFALL
EFFICIENCY OVER 2.5"/HR LIKELY TO PRODUCE FLASH FLOODING OVER
AREAS ALREADY SATURATED FROM EARLIER ONSHORE RAINS.

DISCUSSION...ENCROACHMENT OF THE FRONT ZONE ALONG THE NE SC AND S
NC COASTAL ZONE DUE TO A WEAK HIGHLY ELONGATED/SHEARED SURFACE
WAVE 
THAT HAS FOCUSED LOW LEVEL FLOW AND MST CONVERGENCE.  STRONG
MERIDIONAL JET ALOFT IS SHIFTING WEST A BIT WITH AN EXITING JET
STREAK TOWARD VA...ALLOWING FOR RIGHT ENTRANCE REGION DIVERGENCE
TO SUPPORT THIS LOW AND DEEPER CONVECTIVE GROWTH SEEN IN VISIBLE
AND IR.  IR TOPS ARE COOLING AND EXPANDING IN A WEDGE WITH
SCATTERED -65 TO -70C COOLING TOPS.  ALLOWING FOR INCREASED
RAINFALL EFFICIENCY AND THE POTENTIAL FOR RATES IN EXCESS OF
2.5"/HR.  GIVEN THE AREA/PARTICULARLY THE COASTAL COUNTIES HAVE
BEEN RECEIVING PERSISTENT MODERATE RAINS THAT HAVE ALLOWED FOR
LOCAL RIVERS/STREAMS TO SWELL POTENTIALLY COMPOUNDED BY INCREASED
COASTAL FLOODING NOT ALLOWING WATERS TO DRAIN.   SO AT THIS POINT
THESE HIGHER RATES ARE LIKELY TO LEAD TO LOCALIZED FLASH
FLOODING/INUNDATION CONCERNS.   

STRONG 30-40 KT PERPENDICULAR ONSHORE FLOW LIFTING OVER THE
BOUNDARY BUT DEEP SOUTHERLY FLOW THROUGH MUCH OF THE STEERING FLOW
FOR THE DEEPER CELLS...THE LIKELIHOOD OF A PERSISTENT CONVECTIVE
INITIATION POINT NEAR THE COASTAL FRONTAL ZONE AND CELL MOTIONS
DUE NORTH COULD FAVOR A TRAINING PROFILE WITH A SLOW ADVANCEMENT
EASTWARD WITH TIME.  THIS SCENARIO IS SUPPORT THROUGH MUCH OF THE
HI-RES CAMS BUT PARTICULARLY THE 12Z NSSL-WRF...RECENT HRRR AND
ESRL EXPERIMENTAL HRRR RUNS AND 12Z NMMB RUNS.    

FURTHER NORTH...INTO NORTH CAROLINA...WITH REDUCING LOW LEVEL
SUPPORT AND REDUCED INSTABILITIES...HIGH RAIN RATES WILL GENERALLY
REDUCE TO MODERATE .5-1"/HR STRATIFORM RATES...THOUGH LIKELY OVER
A BROADER W-E ZONE.  AGAIN...PROLONGED INUNDATION FLOODING WILL BE
THE PROBLEM HERE AS WELL OVER THE LONGER DURATION. 

GALLINA

ATTN...WFO...CAE...CHS...ILM...RAH...

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

LAT...LON   35697948 35677859 34907828 33987805 33497852 
            32697908 31477976 31968018 33028047 34458050 
            35358003