707
AWUS01 KWNH 010329
FFGMPD
NJZ000-PAZ000-DEZ000-MDZ000-WVZ000-010727-
MESOSCALE PRECIPITATION DISCUSSION 0564
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1128 PM EDT MON JUN 30 2025
AREAS AFFECTED...SOUTHERN/SOUTHEASTERN PENNSYLVANIA AND VICINITY
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY
VALID 010327Z - 010727Z
SUMMARY...ADDITIONAL FLASH FLOOD IMPACTS ARE POSSIBLE AS DEEP,
MOIST CONVECTION MIGRATES FROM WEST-SOUTHWEST TO EAST-NORTHEAST
ACROSS THE REGION. OVER TIME, NOCTURNAL LOW-LEVEL STABILIZATION
SHOULD RESULT IN LESSER COVERAGE OF STORMS THROUGH 07Z.
DISCUSSION...FLASH FLOOD POTENTIAL CONTINUES ACROSS THE DISCUSSION
AREA, WITH SIGNIFICANT IMPACTS NOTED IN/NEAR LANCASTER COUNTY, PA
RECENTLY. THE REGION REMAINS UNDER THE INFLUENCE OF WEAK
MID-LEVEL SHORTWAVE TROUGHS PASSING OVER THE REGION. THESE
TROUGHS WERE INTERACTING WITH A VERY MOIST, UNSTABLE AIRMASS (2+
INCH PW VALUES AND 1000+ J/KG MLCAPE) TO PROMOTE SCATTERED TO
WIDESPREAD THUNDERSTORM DEVELOPMENT. SOME OF THESE STORMS WERE
TRAINING, WITH 1-2 INCH/HR RAIN RATES FALLING NEAR LANCASTER,
READING, AND SURROUNDING LOCALES ON TOP OF SATURATED GROUNDS THAT
HAVE ALREADY EXPERIENCED 2-6 INCHES OF RAINFALL TODAY. LOCALLY
SIGNIFICANT FLASH FLOOD IMPACTS ARE EXPECTED TO CONTINUE IN THE
SHORT TERM (THROUGH 05-06Z).
OVER TIME, NOCTURNAL BOUNDARY LAYER STABILIZATION SHOULD RESULT IN
A DECREASE IN CONVECTIVE COVERAGE ACROSS THE DISCUSSION AREA.
HOWEVER, LOW-LEVEL FLOW INTO THE DISCUSSION AREA REMAINS STRONG
(25-30 KTS AT 850MB) AND A POOL OF 2000+ J/KG MLCAPE RESIDES OVER
MARYLAND JUST SOUTH OF ONGOING, STRONG CONVECTION. MID/UPPER
LEVEL FIELDS ALSO AREN'T NECESSARILY PROHIBITIVE OF ANY
REDEVELOPMENT OF CONVECTION THROUGH THE NIGHT. ALTHOUGH
CONVECTIVE COVERAGE IS EXPECTED TO DECREASE SOME OVER THE NEXT 2-4
HOURS, SENSITIVE AREAS OF SOUTHEASTERN PENNSYLVANIA (ESPECIALLY
THOSE THAT ARE ALREADY EXPERIENCING SIGNIFICANT FLASH FLOOD
IMPACTS) WILL NEED TO BE MONITORED CAREFULLY FOR ADDITIONAL HEAVY
RAINFALL EPISODES THROUGH 07Z/3A EDT.
COOK
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
ATTN...WFO...BGM...CTP...LWX...PBZ...PHI...
ATTN...RFC...RHA...TIR...NWC...
LAT...LON 41417691 41187566 40497462 39847443 39317530
39267695 39767837 40417905 41237832
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page