A nearly stationary frontal boundary acted as a focus for a severe thunderstorm and heavy rain across southeastern Pennsylvania on the afternoon of the 18th.
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Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS PHI wrote it up.
A nearly stationary frontal boundary acted as a focus for a severe thunderstorm and heavy rain across southeastern Pennsylvania on the afternoon of the 18th.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at Jul 18, 9:50 AM EST, 2 hours 10 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1050 AM EDT WED JUL 18 2007 .SYNOPSIS... A WEAK WARM FRONT CONTINUES TO MOVE NORTH ACROSS THE FORECAST AREA THIS MORNING. A SLOW MOVING COLD FRONT WILL APPROACH FROM THE WEST THURSDAY AND CROSS THE REGION THURSDAY NIGHT INTO EARLY FRIDAY. HIGH PRESSURE WILL FOLLOW THE FRONT FOR THE WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... OUR FIRST BATCH OF SHOWERS AND THUNDERSTORMS HAVE, FOR THE MOST PART, MOVED INTO OUR NORTHERN COASTAL WATERS LATE THIS MORNING. THERE ARE OTHER SCATTERED SHOWERS OVERTHE NORTHERN PART OF THE AREA, WHILE ELSEWHERE THERE ONLY ARE ISOLATED SHOWERS. WE STILL SEE, ON WATER VAPOR IMAGERY, THE SHORT WAVE TO OUR WEST THAT MAY TRIGGER MORE ACTIVITY THIS AFTERNOON. THE TIMING OF THE 06Z RUNS SUGGEST THAT THIS MAY CLEAR OUR REGION BEFORE DUSK. THERE IS AN UPPER JET ASSOCIATED WITH THE SHORT WAVE. OUR SURFACE DEWPOINTS ARE FAIRLY HIGH, SO EVEN THOUGH WE HAVE A FAIR AMOUNT OF CLOUDINESS AROUND LAPS IS ALREADY GIVING US CAPES ABOVE 1000 J/KG OVER THE CENTRAL AND SOUTHERN ZONES. BETWEEN THE SHORT WAVE, THE UPPER SUPPORT, AND THE MOISTURE LADEN INSTABILITY, THE HIGH CHANCE POPS AND THE ENHANCED WORDING LOOK FINE. LOCALIZED HEAVY DOWNPOURS ALSO ARE POSSIBLE GIVEN THE PWATER VALUES AROUND 1.75 INCHES. SPC MAINTAINS MOST OF THE AREA IN A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON. THE CLOUDS MAY MAKE THE HIGHER MAV FCST MAXES A LITTLE HIGH, AND THE MORNING SOUNDINGS SUGGEST GOING WITH THE COOLER MET GUIDANCE, BUT GIVEN THE TIME OF YEAR WEVE JUST SPLIT THE DIFFERENCE RATHER THAN GO TOO COOL. WITH REGARD TO THE PREVIOUS FORECAST, THIS ONLY INVOLVED EXPANDING THE RANGE OF THE MAXIMUM TEMPS A LITTLE ON THE LOW SIDE. && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/... ONCE WE LOSE THE HEATING THIS EVENING, THE SHOWER AND TSTM ACTIVITY, ALONG WITH THE THREAT OF SEVERE WEATHER, WILL DIMINISH. CANT RULE OUT A STRAY SHOWER OR TSTM LATER AT NIGHT OR THURSDAY MRNG, SO WILL CONTINUE TO CARRY CHC POPS. SHOULD HAVE MORE SUN THURSDAY THAN TODAY, SO EXPECT HIGHER TEMPERATURES. STILL A VERY UNSTABLE AIRMASS, AND WITH APPROACHING FRONT, COULD HAVE STRONG TSTMS LATE THURSDAY INTO THURSDAY NIGHT. SPC ONCE AGAIN HAS MUCH OF OUR AREA IN A SLIGHT RISK FOR SEVERE. COULD BE SOME VERY HEAVY RAIN WITH THESE STORMS ALSO, ESPECIALLY NORTH. THE FRONT SHOULD REACH EASTERN PORTIONS OF THE FORECAST AREA BY DAYBREAK FRIDAY. THIS IS WHERE THE MODELS DIVERGE. THE NAM STALLS THE FRONT JUST TO OUR SOUTH AND EAST AND DEVELOPS A WAVE, WHEREAS THE GFS IS VERY PROGRESSIVE AND MOVES THE FRONT OFF THE COAST FRIDAY AND END THE PRECIPITATION BY MIDDAY FRIDAY. FOR NOW, WELL TONE DOWN THE MENTION OF PRECIPITATION IN OUR FORECAST, BUT STILL KEEP CHC POPS FOR FRIDAY AND FRIDAY NIGHT. WILL DROP POPS TO SLIGHT CHC FOR SATURDAY. && .LONG TERM /FRIDAY THROUGH TUESDAY/... THE FRONT SHOULD REACH EASTERN PORTIONS OF THE FORECAST AREA BY DAYBREAK FRIDAY. THIS IS WHERE THE MODELS DIVERGE. THE NAM STALLS THE FRONT JUST TO OUR SOUTH AND EAST AND DEVELOPS A WAVE, WHEREAS THE GFS IS VERY PROGRESSIVE AND MOVES THE FRONT OFF THE COAST FRIDAY AND ENDS THE PRECIPITATION BY MIDDAY. FOR NOW, WELL TONE DOWN THE MENTION OF PRECIPITATION IN OUR FORECAST, BUT STILL KEEP CHC POPS FOR FRIDAY AND FRIDAY NIGHT. WILL DROP POPS TO SLIGHT CHC FOR SATURDAY. WILL LET THE DAY SHIFT SORT THROUGH THE NEW HPC GUIDANCE BEFORE MAKING ANY WHOLESALE CHANGES. THE HIGH PRESSURE SETTLES IN OVER THE WEEKEND AND WILL CONTINUE TO INFLUENCE OUR WEATHER THROUGH THE EARLY PART OF NEXT WEEK. THE NEXT SHORT WAVE AND SURFACE FRONT MAY TOUCH OFF SHOWERS AND TSTMS TUESDAY. && .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/... FOLLOWING RADAR TRENDS, MOST OF THE SHOWERS AND SCTD TSTMS LOOK LIKE THEY WILL AFFECT THE ABE/RDG TAF SITES. FARTHER SOUTH, NOT MUCH PCPN IS OBS, ALTHOUGH THERE WERE SOME ISOLATED SHOWERS FORMING IN CENTRAL MD. FOLLOWING THE GFS WHICH SEEMS TO FIT TRENDS BETTER THAN THE NAM, MEANS FOLLOWING AN OPTIMISTIC FCST FOR MOST TAF SITES. THERE WILL BE HAZE AND LIGHT FOG THROUGHOUT THE REGION THIS MORNING WITH VSBY MAINLY 3-5 MI, ALTHOUGH PATCHY IFR FOG WILL ALSO SHOW UP. THE CLOUDS OVERHEAD SHOULD LIMIT ANY DENSER FOG FROM FORMING. THE SHOWERS AND ISOLATED TSTMS NORTH SHOULD ALSO CAUSE CIG 2-3 THSD FT WITH VSBY ARND 3 MI, BUT IFR CONDITIONS WILL PROBABLY OCCUR IS TSTMS MAKE IT TO ABE/RDG. NEW SHOWERS COULD ALSO FORM SOUTH, BUT THEY DO NOT LOOK LIKE THEY WILL BE AS WIDESPREAD AS FARTHER NORTH. LATER THIS MORNING, THE SHORT WAVE THAT GENERATED THE EARLY MRNG PCPN LOOKS TO SHIFT TO THE N/E. HOWEVER, A LEFTOVER FRONTAL BOUNDARY SHOULD KEEP SCATTERED SHOWERS NEARBY, ESP ABE/RDG. THEN THE DAYTIME WARMTH WILL ADD TO THE INSTABILITY OVER THE REGION ALLOWING TSTMS TO REFORM AS ANOTHER SHORT WAVE MOVES THROUGH. SHOWERS AND TSTMS THIS AFTN COULD CAUSE IFR CONDITIONS AND SOME OF THE TSTMS MIGHT EVEN BECOME SEVERE. TONIGHT, SOME TRANQUILITY REDEVELOPS, AS TSTMS THAT FORM THIS AFTN SHOULD MOVE E AND DISSIPATE AFTER DARK. LIGHT FOG SHOULD FOG LATE TNGT WITH MVFR CONDITIONS. HOWEVER, WHEREVER RAIN DOES FORM, VSBY COULD DROP BELOW 1 MI IN FOG. DUE TO THE UNCERTAINTY, FOR NOW, THE LOW VSBY FOG WILL BE LEFT OUT OF THE TAF FORECASTS. LOOKING BEYOND 12Z THURSDAY...SCATTERED TSTMS ARE AGAIN EXPECTED THURSDAY INTO FRIDAY. SOME TSTMS COULD BECOME SVR THU AFTN AND EVENING. && .MARINE... A WARM FRONT MOVED NORTH OF THE REGION AND A SOUTHERLY FLOW HAS DEVELOPED. THE FLOW WILL REMAIN SOUTH TO SOUTHWEST THROUGH THURSDAY NIGHT. A COLD FRONT IS THEN EXPECTED TO MOVE THROUGH FROM THE NORTHWEST ON FRIDAY ALLOWING WINDS TO SHIFT TO WEST OR NORTHWEST. DUE TO AN INVERSION ON THE WATER, WIND SPEEDS LOOK LIKE THEY REMAIN UNDER 20 KTS THROUGH TONIGHT. HOWEVER, THE GRADIENT INCREASES THURSDAY NIGHT AHEAD OF THE COLD FRONT AND WIND SPEEDS MAY INCREASE TO 25 KT AND SEAS ON THE OCEAN COULD GET TO 5 FT. A SMALL CRAFT ADVISORY MAY EVENTUALLY BE NEEDED FOR THURSDAY NIGHT. TSTMS ARE POSSIBLE UNTIL THE COLD FRONT MOVES THROUGH ON FRIDAY. SOME OF THE TSTMS COULD BECOME SVR ON LAND AND THEN MOVE OVER THE FORECAST WATERS LATER TODAY AND AGAIN ON THURSDAY. WINDS AND SEAS SHOULD DECREASE BEHIND THE COLD FRONT FRIDAY WITH SPEEDS AND SEAS EXPECTED TO BE BELOW SCA CRITERIA NEXT WEEKEND. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && SYNOPSIS...RPW NEAR TERM...RPW/DELISI SHORT TERM...RPW LONG TERM...RPW/GIGI AVIATION...RNS MARINE...RNS
HAZARDOUS WEATHER OUTLOOK...UPDATED NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1103 AM EDT WED JUL 18 2007 DEZ001>004-MDZ008-012-015-019-020-NJZ001-007>010-012>027-PAZ054-055- 060>062-067>071-191000- NEW CASTLE-KENT DE-INLAND SUSSEX-DELAWARE BEACHES-CECIL-KENT MD- QUEEN ANNES-TALBOT-CAROLINE-SUSSEX-WARREN-MORRIS-HUNTERDON-SOMERSET- MIDDLESEX-WESTERN MONMOUTH-EASTERN MONMOUTH-MERCER-SALEM-GLOUCESTER- CAMDEN-NORTHWESTERN BURLINGTON-OCEAN-CUMBERLAND-ATLANTIC-CAPE MAY- ATLANTIC COASTAL CAPE MAY-COASTAL ATLANTIC-COASTAL OCEAN- SOUTHEASTERN BURLINGTON-CARBON-MONROE-BERKS-LEHIGH-NORTHAMPTON- CHESTER-MONTGOMERY-BUCKS-DELAWARE-PHILADELPHIA- 1103 AM EDT WED JUL 18 2007 THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL DELAWARE...NORTHERN DELAWARE...SOUTHERN DELAWARE...EASTERN MARYLAND...NORTHEAST MARYLAND...CENTRAL NEW JERSEY...NORTHERN NEW JERSEY...SOUTHERN NEW JERSEY...EAST CENTRAL PENNSYLVANIA...NORTHEAST PENNSYLVANIA AND SOUTHEAST PENNSYLVANIA. .DAY ONE...THIS AFTERNOON AND TONIGHT THUNDERSTORMS ARE POSSIBLE THROUGH TONIGHT. SOME OF THE STRONGER STORMS MAY CONTAIN DAMAGING WINDS AND HAIL THIS AFTERNOON INTO EARLY TONIGHT. THEY ALSO MAY CONTAIN HEAVY DOWNPOURS THAT WOULD LEAD TO LOCALIZED FLOODING. ALL THUNDERSTORMS CAN GENERATE DANGEROUS CLOUD TO GROUND LIGHTNING. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY THUNDERSTORMS ARE POSSIBLE THURSDAY INTO FRIDAY. SOME OF THE STRONGER STORMS MAY CONTAIN DAMAGING WINDS, HAIL, AND VERY HEAVY RAIN THURSDAY AFTERNOON INTO THURSDAY NIGHT. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE NEEDED. ANZ430-431-450>455-191000- DELAWARE BAY WATERS NORTH OF EAST POINT NJ TO SLAUGHTER BEACH DE- DELAWARE BAY WATERS SOUTH OF EAST POINT NJ TO SLAUGHTER BEACH DE- COASTAL WATERS FROM SANDY HOOK TO MANASQUAN INLET NJ OUT 20 NM- COASTAL WATERS FROM MANASQUAN INLET TO LITTLE EGG INLET NJ OUT 20 NM- COASTAL WATERS FROM LITTLE EGG INLET TO GREAT EGG INLET NJ OUT 20 NM- COASTAL WATERS FROM GREAT EGG INLET TO CAPE MAY NJ OUT 20 NM- COASTAL WATERS FROM CAPE MAY NJ TO CAPE HENLOPEN DE OUT 20 NM- COASTAL WATERS FROM CAPE HENLOPEN TO FENWICK ISLAND DE OUT 20 NM- 1103 AM EDT WED JUL 18 2007 THIS HAZARDOUS WEATHER OUTLOOK IS FOR ATLANTIC COASTAL WATERS AND DELAWARE BAY WATERS. .DAY ONE...THIS AFTERNOON AND TONIGHT THUNDERSTORMS ARE POSSIBLE THROUGH TONIGHT. SOME OF THE STRONGER STORMS MAY CONTAIN DAMAGING WINDS AND HAIL THIS AFTERNOON INTO EARLY TONIGHT. ALL THUNDERSTORMS CAN GENERATE DANGEROUS CLOUD TO SURFACE LIGHTNING. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY THUNDERSTORMS ARE POSSIBLE THURSDAY INTO FRIDAY. SOME OF THE STRONGER STORMS MAY CONTAIN DAMAGING WINDS, HAIL, AND VERY HEAVY RAIN THURSDAY AFTERNOON INTO THURSDAY NIGHT. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE NEEDED. RPW/MPD
The national radar mosaic for the moment the first event began.
2 heavy rain. Local standard time, as filed.
Heavy rain caused poor drainage flooding in Radnor Township during the afternoon of the 18th. A parking lot in the Wayne section of the township had waist high water. Doppler Radar storm total estimates were around one inch.
In addition to the severe weather, heavy rain also accompanied the thunderstorm in and around Bristol Township. A pick-up truck became stuck in flood waters under a railroad bridge in the township.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Pennsylvania in 2007Every state in 2007This day in weather historyWarnings in Pennsylvania, July 2007
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 52676, 52309.