171
AWUS01 KWNH 050059
FFGMPD
NJZ000-PAZ000-DEZ000-MDZ000-050627-
MESOSCALE PRECIPITATION DISCUSSION 1205
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
857 PM EDT FRI SEP 04 2026
AREAS AFFECTED...SOUTHEAST PA, SOUTHERN NJ, & DE
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE
VALID 050057Z - 050627Z
SUMMARY...SHOWERS AND THUNDERSTORMS ARE EXPECTED TO INTENSIFY AND
GROW IN SCALE AS THEY MOVE SOUTHEAST. HOURLY RAIN AMOUNTS TO 2"
WITH LOCAL TOTALS TO 4" ARE POSSIBLE, WHICH COULD LEAD TO FLASH
FLOODING.
DISCUSSION...SOME SHOWER AND THUNDERSTORM ACTIVITY HAS RECENTLY
FORMED ACROSS CENTRAL PA, WHOSE MOTION IS NOT QUITE ALIGNED IN A
TRAINING MANNER. IT IS FORMING WITHIN A MU CAPE GRADIENT WHICH IS
SLOWLY SETTLING SOUTHWARD AND IS ORIENTED NORTHWEST- SOUTHEAST
WITHIN AN AREA OF 850 HPA CONFLUENCE. EFFECTIVE BULK SHEAR IS
30-40 KTS. MU CAPE IS 500-1000 J/KG.
THE LOW-LEVEL CONVERGENCE ZONE SHOULD SETTLE SOMEWHAT SOUTHWARD
WITH TIME. BOTH THE 18Z HREF AND 12Z REFS HAVE A SIGNAL FOR THIS
ACTIVITY WHICH APPEARS TO BE FORMING RIGHT ON THEIR SCHEDULE.
WITH TIME, ADDITIONAL SHOWERS AND THUNDERSTORMS ARE EXPECTED TO
FORM WITH THE ACTIVITY POTENTIALLY GROWING IN SCALE INTO A SMALL
CONVECTIVE COMPLEX AS IT MOVES SOUTHEAST, WHICH COULD LEAD TO CELL
TRAINING/MERGERS. THE MAGNITUDE OF EFFECTIVE BULK SHEAR ALLOWS
FOR MESOCYCLONES AS WELL. MOST OF THE GUIDANCE THAT ADVERTISES
HEAVY RAINFALL IN THIS REGION DOESN'T ENHANCE THIS ACTIVITY
SIGNIFICANTLY UNTIL RIGHT AFTER IT PASSES OUT OF SOUTHEAST PA, BUT
IT'S TOO CLOSE FOR COMFORT. GIVEN THE MOISTURE AVAILABLE, HOURLY
RAIN AMOUNTS TO 2" WITH LOCAL TOTALS TO 4" ARE POSSIBLE. THIS
DEGREE OF RAINFALL COULD EXCEED THE THREE HOUR FLASH FLOOD
GUIDANCE VALUES, PARTICULARLY ACROSS SOUTHEAST PA. FLASH FLOODING
IS CONSIDERED POSSIBLE.
ROTH
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...AKQ...CTP...LWX...PHI...
ATTN...RFC...RHA...NWC...
LAT...LON 41367825 41137708 39867489 39347432 39147462
38907473 38807497 38407502 38497573 39677716
40987831
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