MESOSCALE PRECIPITATION DISCUSSION 0520
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
311 AM EDT MON JUL 23 2018

AREAS AFFECTED...EASTERN NC & SOUTHEAST VA

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

VALID 230710Z - 231310Z

SUMMARY...THUNDERSTORMS WITH HEAVY RAIN ARE EXPECTED TO
OCCASIONALLY TRAIN ACROSS EASTERN NC AND PERHAPS FAR SOUTHEAST VA.
 HOURLY RAIN TOTALS TO 2" WITH LOCAL AMOUNTS TO 4" ARE EXPECTED.

DISCUSSION...WELL-DEFINED UPPER LEVEL SHORTWAVES ACROSS NC AND GA
ARE TRYING TO ALIGN INTO A MORE ZERO TILT CONFIGURATION ALOFT,
WHICH IS BROADENING THE DIVERGENCE SIGNATURE ALOFT ON RECENT
SATELLITE IMAGERY.  A SURFACE TROUGH LIES ACROSS EASTERN NC WHICH
HAS BEEN ACTING AS THE FOCUS FOR CONVECTION THUS FAR.  INFLOW AT
850 HPA IS SLOWLY BACKING, NOW EAST OF DUE SOUTH AT 25-35 KTS PER
VAD WIND PROFILES AND RAP ANALYSES.  EFFECTIVE BULK SHEAR IS ~30
KTS, WHICH ALONG WITH THE UNIDIRECTIONAL FLOW WITH HEIGHT HAS LED
TO TRAINING BANDS ON OCCASION.  ML CAPE VALUES OF 1000-2000 J/KG
LIE ACROSS THE REGION; CIN IS MINIMAL.  PRECIPITABLE WATER VALUES
ARE ~2" PER GPS DATA.

A PAIR OF MESOSCALE CIRCULATIONS OFFSHORE SOUTHERN NC APPEAR TO BE
TRYING TO PULL THE CURRENT CONVECTIVE BAND ONTO A MORE WESTERLY
TRAJECTORY, SIMILAR TO WHAT IS ADVERTISED BY THE 00Z HREF
PROBABILITIES OF 1"+ AN HOUR AND THE 00Z WRF NSSL.  STORMS SHOULD
MOVE ASHORE CARTARET COUNTY SHORTLY WHICH COULD PULL THE BAND
CURRENTLY ACROSS DARE COUNTY MORE WESTWARD WITH TIME, WHICH COULD
BE HELPED OUT BY THE SOUTH-SOUTHEAST LOW-LEVEL FLOW.  OTHER
THUNDERSTORM ACTIVITY TO THE WEST MAY OCCASIONALLY MERGE IN AS
WELL.  HOWEVER, BY 12Z, RAP FORECASTS INDICATE THAT THE BAND COULD
MOVE EASTWARD ONCE MORE AS THE FLOW VEERS SLIGHTLY.  THE IMPACT ON
NORFOLK VA IS UNCLEAR AS THEY'VE BEEN CLIPPED BY HEAVY RAINFALL
ALL NIGHT.  OTHERWISE, THE GUIDANCE AGREES ON THE POTENTIAL OF
LOCAL MAXIMA OF 4" THROUGH 13Z.  LOWERED THE CATEGORY TO POSSIBLE
AS THE MESOSCALE GUIDANCE SHOWS A BIT MORE DISPERSION WITH
EXPECTATIONS THAN SEEN SEVERAL HOURS AGO.

ROTH

ATTN...WFO...AKQ...MHX...

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

LAT...LON   37547559 36867590 36427576 36087563 35677541
            35197543 35067585 34757619 34557645 34617671
            35427672 36257657 37117617 37377592