166
AWUS01 KWNH 072155
FFGMPD
NCZ000-SCZ000-FLZ000-GAZ000-080330-
MESOSCALE PRECIPITATION DISCUSSION 1060
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
554 PM EDT SUN SEP 07 2025
AREAS AFFECTED...COASTAL PLAIN FROM CENTRAL FLORIDA TO EASTERN
NORTH CAROLINA
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 072154Z - 080330Z
SUMMARY...SLOW MOVING SHOWERS AND THUNDERSTORMS WILL PERSIST
THROUGH EVENING ALONG A STALLED COLD FRONT. RAINFALL RATES OF
2-3"/HR ARE EXPECTED TO BE COMMON, WHICH THROUGH THIS SLOW STORM
MOTION COULD PRODUCE 2-4+" OF RAINFALL. THIS MAY RESULT IN FLASH
FLOODING, ESPECIALLY ACROSS URBAN AREAS.
DISCUSSION...THE REGIONAL RADAR MOSAIC THIS EVENING INDICATES A
CONTINUED EXPANSION OF SHOWERS AND THUNDERSTORMS FROM THE CENTRAL
FLORIDA PENINSULA NORTHEAST ALONG THE COASTAL PLAIN THROUGH CAPE
LOOKOUT, NC. THIS ACTIVITY IS BLOSSOMING ALONG A COLD FRONT, WHICH
HAS MERGED IN PLACES WITH THE SEA BREEZE TO STALL NEAR THE COAST.
THE COMBINED ASCENT ALONG THIS BOUNDARY IS THE PRIMARY FOCUS FOR
CONVECTIVE DEVELOPMENT, ALTHOUGH A WEAK SHORTWAVE NOTED ACROSS THE
FL PANHANDLE IS LIFTING NORTHEAST DOWNSTREAM OF AN ANOMALOUS
TROUGH AXIS TO PROVIDE ADDITIONAL ASCENT.
THIS LIFT IS ACTING UPON A RICH THERMODYNAMIC ENVIRONMENT
CHARACTERIZED BY PWS MEASURED BY GPS OF 1.8 TO 2.0 INCHES,
OVERLAPPING POCKETS OF SBCAPE ANALYZED BY THE SPC RAP THAT ARE
ABOVE 2000 J/KG WHERE CONVECTIVE OVERTURNING HAS YET TO OCCUR. THE
PRESENCE OF THIS STEADY ASCENT INTO THIS ROBUST AIRMASS HAS
PRODUCED SCATTERED THUNDERSTORMS WITH RAINFALL RATES ESTIMATED BY
THE LOCAL RADARS OF AS MUCH AS 2.5"/HR, AND MEASURED VIA
OBSERVATIONS AND MRMS TO BE AS MUCH AS 3" IN 1 HOUR. THIS HAS
RESULTED IN ISOLATED FLASH FLOODING NEAR THE CITY OF CHARLESTON,
SC ALREADY THIS AFTN.
THE CAMS WERE SLOW TO PICK UP ON THE UPTICK IN ACTIVITY, BUT HAVE
STARTED TO SUPPORT A MORE WIDESPREAD HEAVY RAINFALL EVENT INTO
THIS EVENING BEFORE LOSS OF HEATING/INSTABILITY OCCURS. HREF
NEIGHBORHOOD PROBABILITIES FOR 2"/HR RATES PEAK ABOVE 40% THROUGH
01Z, COINCIDENT WITH LOSS OF INSTABILITY AND FINALLY A SLOW PUSH
EAST OF THE COLD FRONT. UNTIL THAT OCCURS, HOWEVER, WIDESPREAD
THUNDERSTORMS ARE LIKELY, AND ALTHOUGH MOST SHOULD BE OF THE PULSE
VARIETY, SOME INCREASED BULK SHEAR TO 20-25 KTS IN THE VICINITY OF
THE MID-LEVEL SHORTWAVE COULD ORGANIZE THUNDERSTORMS INTO CLUSTERS
TO ENHANCE RAINFALL RATES TO LOCALLY AS MUCH AS 1"/15 MIN (BRIEF
4"/HR RATES). WEAK STORM MOTIONS AS REFLECTED BY JUST 5 KTS OF
0-6KM MEAN WINDS AND ALIGNED CORFIDI VECTORS SUGGEST THAT STORMS
COULD BUILD SW ALONG THE FRONT AND INTO SOME MORE IMPRESSIVE
THERMODYNAMICS, BEFORE TRAINING E/NE FROM NORTHEAST FL THROUGH
EASTERN NC. THIS COULD RESULT IN LOCAL RAINFALL TOTALS APPROACHING
4-5 INCHES.
ALTHOUGH THIS AREA HAS BEEN EXTREMELY DRY (0% RAINFALL THE PAST 7
DAYS ACCORDING TO AHPS OUTSIDE OF PARTS OF THE FL PENINUSULA),
THESE INTENSE RAIN RATES COULD STILL OVERWHELM SOILS LEADING TO
RAPID RUNOFF. THIS WILL BE MOST LIKELY ACROSS URBAN AREAS, BUT
SOME VULNERABILITY EXISTS EVEN OUTSIDE OF THE POPULATION CENTERS
SHOULD ANY OF THESE INTENSE RAINFALL RATES TRAIN REPEATEDLY ACROSS
ANY GIVEN AREA. THIS SUGGESTS THAT FLASH FLOODING REMAINS POSSIBLE
THROUGH THE EVENING, BUT THE RISK SHOULD WANE RAPIDLY AFTER DARK.
WEISS
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...CAE...CHS...FFC...ILM...JAX...MHX...MLB...RAH...
TBW...
ATTN...RFC...ALR...NWC...
LAT...LON 35127693 35057628 34767613 34507629 34317677
33967757 33637817 32927909 32397992 31758063
30988099 29938085 29198046 28348046 28238099
28338144 28758196 29468244 30138278 31128273
32238221 33198104 34057989 34557865 34947770
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