854
AWUS01 KWNH 160833
FFGMPD
VAZ000-NCZ000-161400-
MESOSCALE PRECIPITATION DISCUSSION 1090
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
432 AM EDT TUE SEP 16 2025
AREAS AFFECTED...COASTAL SOUTHEASTERN VA AND NORTHEASTERN NC
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 160831Z - 161400Z
SUMMARY...AT LEAST A LOCALIZED FLASH FLOOD THREAT LOOKS TO BE
INCREASING ACROSS COASTAL SECTIONS OF SOUTHEASTERN VA AND
NORTHEASTERN NC THIS MORNING. INCREASING RAINFALL RATES WITH
HOURLY TOTALS POTENTIALLY REACHING 3 INCHES ARE EXPECTED TO IMPACT
A FEW COASTAL LOCATIONS THROUGH 14Z.
DISCUSSION...08Z SURFACE OBSERVATIONS AND SHORTWAVE IR IMAGERY
FROM GOES EAST SHOWED A SURFACE LOW CENTERED ABOUT 65 MILES EAST
OF CAPE HATTERAS. OVER THE PAST 6 HOURS, THE SURFACE LOW HAS BEEN
GRADUALLY LIFTING NORTH TO NORTHWEST WHILE OCCASIONAL MESOSCALE
LOWS HAVE APPEARED IN THE BROADER LOW LEVEL CLOUD SWIRL IN
SATELLITE IMAGERY. IT APPEARS THE MAIN SURFACE LOW HAS BEEN
ASSOCIATED WITH THE MOST RECENT BURST OF CONVECTION TO ITS
NORTHWEST, WITH AREA RADAR IMAGERY SHOWING REFLECTIVITY ECHOES
CROSSING OVER HATTERAS ISLAND. SPC MESOANALYSIS DATA FROM 08Z
SHOWED THE CONVECTIVE BURST ALONG THE WESTERN EDGE OF A MLCAPE
BUBBLE OFFSHORE WITHIN 1000-2000 J/KG, JUST EAST OF THE NORTHERN
OUTER BANKS. MEANWHILE, MODERATE TO OCCASIONALLY HEAVY RAIN HAS
BEEN OBSERVED OVER VA, TO THE SOUTHWEST OF NORFOLK, WITH 1-2
INCHES REPORTED SINCE MIDNIGHT. HOWEVER, A LACK OF BETTER
INSTABILITY HAS LIMITED RAINFALL INTENSITY FOR INLAND LOCATIONS.
SHORT TERM RAP GUIDANCE OVER THE PAST 6-10 CYCLES HAS BEEN IN
RELATIVELY GOOD AGREEMENT WITH THE CURRENT SURFACE LOW POSITION
AND SUPPORTS THE LOW TRACKING TOWARD THE NORTHWEST, CLOSER TO THE
OUTER BANKS, THROUGH 14Z. THIS MOVEMENT MAKES SENSE GIVEN THE
LOW'S PLACEMENT RELATIVE TO A CLOSED MID-LEVEL LOW CENTERED OVER
THE CENTRAL NC/SC BORDER. EVEN IF THE RAP IS WRONG, THERE IS THE
POTENTIAL FOR CONVECTIVELY INDUCED MESOVORTICES WITHIN CONVECTION
THAT MAY REACH THE COAST BEFORE DISSIPATING. AN EXPECTED
NORTHWESTWARD MOVEMENT OF THE SURFACE LOW SHOULD SUPPORT
INCREASING MLCAPE FROM ROUGHLY CAPE HATTERAS TO VIRGINIA BEACH
WITH VALUES OF 500 J/KG TO THE NORTH AND UP TO ~1500 J/KG OVER
HATTERAS ISLAND BY 12-14Z. IN ADDITION, A PRIMARY AXIS OF LOW
LEVEL CONVERGENCE TO THE NORTHWEST OF THE LOW CENTER IS EXPECTED
TO MAKE IT TO THE NORTHEASTERN NC AND SOUTHEASTERN VA COAST WITH
INCREASING RAINFALL INTENSITIES BENEATH FAVORABLY DIFFLUENT FLOW
IN THE UPPER LEVELS. ADDITIONAL, WEAKER AND MORE TRANSIENT AXES OF
LOW LEVEL CONVERGENCE WILL BE POSSIBLE FARTHER INLAND FROM THE
COAST WHICH COULD SUPPORT INCREASED RAINFALL INTENSITIES AS
INSTABILITY INCREASES LATER THIS MORNING.
EARLIER GAUGE OBSERVATIONS HAD SHOWN ~0.75 INCHES OF RAIN IN 15
MINUTES WHICH WOULD SUPPORT HOURLY RAINFALL UP TO 3 INCHES.
EXPECTED HOURLY RAINFALL OF 1 TO 3 INCHES WILL BE POSSIBLE FROM
PORTIONS OF NORTHEASTERN NC INTO SOUTHEASTERN VA WHICH MAY RESULT
IN LOCALIZED FLASH FLOODING, ESPECIALLY OVER ANY URBAN LOCATIONS.
OTTO
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...AKQ...MHX...RAH...
ATTN...RFC...ALR...RHA...NWC...
LAT...LON 37197676 37137627 36787569 35957506 35177532
35167600 35567677 36077735 36497755 37067729
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