A nearly stationary frontal boundary acted as a focusing mechanism for thunderstorms throughout the day on the 29th in eastern Pennsylvania.
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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 focusing mechanism for thunderstorms throughout the day on the 29th in eastern Pennsylvania.
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 28, 10:40 PM EST, 4 hours 30 minutes earlier.
AREA FORECAST DISCUSSION...NEAR TERM CHANGED NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1140 PM EDT SAT JUL 28 2007 .SYNOPSIS... THE UPPER LOW HAS LIFTED NORTHEAST WITH A TROUGH EXTENDING SOUTHWEST INTO OUR REGION. A WEAK SURFACE BOUNDARY WILL LINGER OVER THE REGION TODAY INTO SUNDAY WITH A COUPLE OF LOWS PRESSURES MOVING NORTHEAST ALONG THE FRONT. && .NEAR TERM /THROUGH TONIGHT/... LATEST MSAS AND LAPS SHOWS WE ARE STILL UNSTABLE AND OUTFLOWS OR JUST THE GENERAL DRIFT OF THE TSRAS TO OUR W WARRANT THE CONT OF CHCS ACRS THE SRN PART OF OUR CWA OVERNIGHT. KIND OF LOST ABT THE LACK OF BEEFY QPF ON THE WRF NMM FOR SUN GIVEN JUST THE GENERAL INSTAB. WE/LL ADDRESS THAT LATER. && .SHORT TERM /SUNDAY AND SUNDAY NIGHT/... SUNDAY FROM A METEOROLOGICAL PERSPECTIVE IS THE MORE INTERESTING OF THE TWO WEEKEND DAYS. BUT FROM A PUBLIC PERSPECTIVE IT MAY BE MORE FOREBODING. THERE IS A GENERAL MDL AGREEMENT ON A RELATIVE BASIS OF THE THREE DAYS (TDY/SUN/MON)....SUN HAS THE GREATEST FCSTD INSTAB. THIS IS TRUE IF ONE IS LOOKING AT THE GFS OR WRF-NMM AND AT LEAST THRU ITS RUN TIME PERIOD THE CAN RGEM ALSO AGREES. THE WRF-NMM FCSTS MORE CAPE (2000-3000J), A LOWER L.I. (TO -8C), SLIGHTLY MORE ROBUST TTS AND WEAK THETA E ADVT. THE SREF MEAN FOR SUNDAY IS SIM TO TDY...THE OP WRF MAY BE OVERCOOKING THE GROUND (SAW A 34C AT PHL FOR A 2M TEMP) A LTL BIT. BUT. THE NEXT APCHG SHORT WAVE WILL ONLY ASSIST. PWATS ARE ALSO FCSTD TO REACH CLOSE TO 2. IF ONE WOULD LOOK AT THE WRF-NMM FCSTD WIND FIELD AT PHL FOR SUN AFTN...ITS PRETTY MUCH 0000. EVEN FORWARD PROPAGATING CORFIDI VECTORS ARE ONLY AROUND 10 KTS. THE GFS AT LEAST HAS A BIT MORE WIND, BUT BOTH MDLS SHOW A MORE SATURATED COLUMN OF AIR. THIS MIGHT BE TOO MOIST FOR ORGANIZED SVR WX (AGAIN THE FCSTD MID LVL LAPSE RATES ARE VERY WEAK)...BUT IF THE MDLS ARE JUST OVERDOING THE MID LVL MSTR A BIT...WE WOULD BE POISED FOR SOME WET MICROBURSTS (AS PER LATEST SWODY2). FOR NOW THE GREATER THREAT APPEARS TO BE THE HVY RAIN BECAUSE OF THE LTL FCSTD MOVEMENT. WE WILL ADD THAT WORDING TO THE ZONES. BECAUSE OF THE ADDTIONAL MSTR...BOTH MOS MAX TEMP VALUES WERE FCSTD TO DROP. EVEN IF WE GET JUST ABT 50 PERCENT SUN, WE BELIEVE PHL COULD SEE 90F AGAIN AND WE WILL SIDE WITH THE WRMR GFS MOS. DON/T BELIEVE THE TSRAS WILL GO QUIETLY INTO THE NGT ON SUN NGT AND WE WILL KEEP HIER POPS INTO THE EVE. DEPENDING UPON HOW QUICKLY THE SHORT WAVE EXITS MONDAY WILL HAVE A BEARING ON HOW WET EVENT MONDAY WILL BE. THE FNT WILL STILL BE STRUGGLING TO COME THRU AND WHL THE WRF-NMM IS FASTER...THIS IS THE FIRST SUMMER SYSTEM THAT HAS DRAGGED ITS HEALS. AS SUCH WE WILL HONOR A W-E POP GRADIENT, BUT WON/T BE AS OPTIMISTIC AS THE WRF-NMM. GFS STAB PARAMETERS ARE FCSTD TO BE NOT AS ROBUST AS SUNDAY. NO CHANGE IN AIR MASS AND THUS HIER ETA MOS LOOKS BETTER FOR MAX TEMPS. && .LONG TERM /MONDAY THROUGH SATURDAY/... MONDAY NIGHT APPEARS TO BE THE PERIOD WHEN THE UPPER LOW/TROUGH BEGING TO MOVE EAST. NOT GOING TO BE A FAST MOVE, BUT A MOVE NO LESS. HEIGHTS RISE OVER THE MID WEST IN RESPONSE TO THE BUILDING HOT AIR RIDGE WITH HEIGHTS OW 591DAM WHICH ISNT BLISTERING BY ANY MEANS. THE 576 THICKINGESS HEIGHTS ARE OVER THE OHIA VALLEY WITH THE 582DM OVER THE DESERT WEST. HIGH TEMPERATURES KEEPING THE THERMOMETER ON THE EDGE NEAR 90 DEGREES BUT TOWARD THE END OF THE WEEK, THE GFS WANTS TO BEGIN A HEAT WAVE OVER THE PLAINS AND EASTERN STATES. THE UPPER RIDGE FALLS TO PIECES AS IT MOVES TO THE EAST. THE EASTERN EXTENSION OF THE RIDGE IS ATTEMPTING TO MOVE TO THE ATLANTIC COAST BUT THE HIGH HEAT SHOULD REMAIN WEST. WE FINALLY HAVE THE 576 THICKNESS EDGE MOVE TO PA BY SUNDAY BUT THEN GETS DEPRESSED SOUTH SHORTLY SOUTHTHEREAFTER. AN UNUSUAL ZONAL FLOWS THEN SETS UP TOWARD THE END OF NEXT WEEK. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... CU HAS POPPED THIS AFTERNOON AS EXPECTED WITH THE HAZE IMPROVING FOR NEARLY ALL AREAS. A WEAK BOUNDARY IS LOCATED ACROSS EASTERN PENNSYLVANIA AND THE TAIL END OF A SHORT WAVE WILL MOVE ACROSS THE AREA THIS AFTERNOON AND EARLY EVENING AS THE UPPER-LEVEL LOW CONTINUES TO MOVE INTO NEW ENGLAND AND OPENS UP. 18Z VISIBLE SATELLITE IMAGERY SHOWING A LINE OF BUILDING CU FORMING NORTHWEST OF KRDG AND KABE, AND RADAR NOW SHOWING SOME RETURNS. THIS IS ALONG THE AFOREMENTIONED WEAK BOUNDARY. AT LEAST SCATTERED CONVECTION IS ANTICIPATED ALONG THIS BOUNDARY AND THEN SLOWLY PROPAGATE TO THE EAST. MODEL GUIDANCE STILL SUGGESTING THAT AREAS NORTHWEST OF INTERSTATE 95 HAVE THE BEST CHANCE OF SOME CONVECTION. THEREFORE WE INCLUDED A TEMPO GROUP FOR KABE AND KRDG FOR A FEW HOURS THIS AFTERNOON. FOR THE NEXT SET OF TERMINALS, WE ONLY INCLUDED A VICINITY FOR LATE THIS AFTERNOON AND LEFT NO MENTION OF PRECIPITATION FOR KMIV AND KACY. THE SEA BREEZE FRONT APPEARS TO BE JUST WEST OF KACY THEREFORE PERHAPS AN ISOLATED SHOWER OR THUNDERSTORM POSSIBLE NEARBY. ONCE ANY CONVECTION DWINDLES BY ABOUT MIDNIGHT, THE MAIN FORECAST CHALLENGE IS WITH RESPECT TO CLOUD COVER AND VISIBILITY. BUFKIT SOUNDINGS ALONG WITH THE MOS GUIDANCE ARE IN DISAGREEMENT. THE ETA/NAM BRINGS IN LOW CLOUDS AND SOME FOG OVERNIGHT WHILE THE GFS ONLY HINTS AT SOME LIGHT FOG. WHILE THE NAMS LOW-LEVEL MOISTURE FIELD COULD BE A LITTLE OVERDONE, WE SAW THE DEVELOPMENT OF SOME LOW CLOUDS AND FOG VERY EARLY THIS MORNING. TONIGHT APPEARS TO BE A SIMILAR SETUP WITH NO CHANGE IN AIRMASS ALONG WITH LIGHT WINDS, THEREFORE WE ARE LEANING CLOSER TO THE ETA/NAM GUIDANCE. ANY AREA THAT PICKS UP RAINFALL WILL PROBABLY AIDE IN LOWER CEILINGS AND SOME FOG OVERNIGHT. WITH THE 18Z TAF ISSUANCE, WE BROUGHT CEILINGS DOWN AND VISIBILITY TO JUST TOUCH THE IFR CATEGORY FOR MOST TERMINALS. A LOCALLY FURTHER REDUCTION IN VISIBILITY/CEILINGS CAN OCCUR ESPECIALLY WHERE RAINFALL OCCURS AS THE LOW-LEVEL MOISTURE REMAINS HIGH. ANY LOW CLOUDS AND FOG SHOULD LIFT AROUND 14Z SUNDAY WITH SOME CU AND MID LEVEL CLOUDS FORMING. AT LEAST SCATTERED CONVECTION AROUND AGAIN SUNDAY, MAINLY IN THE AFTERNOON, HOWEVER CONFIDENCE WITH THE TIMING OF THIS IS NOT HIGH ATTM THEREFORE THIS WAS NOT INCLUDED. BEYOND THE TAF PERIOD...THERE WILL BE A CONTINUED CHANCE FOR MAINLY AFTERNOON AND EVENING CONVECTION MONDAY INTO TUESDAY AS A SLOW MOVING COLD FRONT CROSSES THE REGION. A WEAK AREA OF HIGH PRESSURE THEN BUILDS IN FOR WEDNESDAY AND THURSDAY. && .MARINE... NO HEADLINES ARE IN EFFECT. A SOUTHERLY FLOW WILL CONTINUE TO GENERALLY DOMINATE THE MARINE AREA TONIGHT THROUGH MONDAY AS A SLOW MOVING COLD FRONT APPROACHES FROM THE WEST. THIS FRONT IS ANTICIPATED TO SETTLE SOUTH OF THE AREA LATE MONDAY. UNTIL THEN, WE ARE EXPECTING WINDS 15 KNOTS OR LESS FROM A SOUTHERLY DIRECTION. UNDER THIS FAIRLY LIGHT FLOW REGIME, WINDS HAVE SHIFTED TO THE SOUTHEAST ACROSS DELAWARE BAY AND THIS SHOULD ONCE AGAIN OCCUR SUNDAY WITH SOME ENHANCEMENT IN WIND SPEED MAINLY DURING THE AFTERNOON AND EVENING AS INLAND AREAS HEAT UP, SETTING THE STAGE FOR A SEA BREEZE. WINDS SHOULD THEN SHIFT TO A NORTH TO NORTHEAST DIRECTION ON TUESDAY AS THE FRONT SETTLES SOUTH AND A WEAK AREA OF HIGH PRESSURE BUILDS TOWARD THE AREA FROM THE NORTHWEST. SEAS ON THE OCEAN ARE IN THE 2 TO 3 FOOT RANGE /1 TO 2 FEET ON DELAWARE BAY/ AND WAVEWATCH IS HANDLING THIS WELL. THEREFORE, LITTLE CHANGES WERE MADE FROM THE PREVIOUS FORECAST. A FAIRLY TRANQUIL TIME WITH THE EXCEPTION OF LOCALLY GUSTY WINDS AND HIGHER SEAS IN AND AROUND ANY THUNDERSTORMS THE NEXT DAY OR TWO. RIP CURRENTS...LOCATIONS ALONG COASTAL ATLANTIC AND ATLANTIC COASTAL CAPE MAY COUNTIES REMAIN UNDER A MODERATE RISK INTO THIS EVENING DUE TO THE SOUTHEASTERLY FLOW PRODUCING LOCALLY ENHANCED RIP CURRENTS. THIS IS SIMILAR TO WHAT OCCURRED ON FRIDAY. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && SYNOPSIS...JAE NEAR TERM...TFG SHORT TERM...JAE LONG TERM...JAE AVIATION...GORSE MARINE...GORSE
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 400 AM EDT SUN JUL 29 2007 DEZ001>004-MDZ008-012-015-019-020-NJZ001-007>010-012>027-PAZ054-055- 060>062-067>071-301000- 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- 400 AM EDT SUN JUL 29 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...TODAY AND TONIGHT LOCALLY HEAVY RAIN WILL CAUSE URBAN AND POOR DRAINAGE FLOODING THROUGH TONIGHT AND MAY CAUSE SOME ROAD CLOSURES. WHILE A FLASH FLOOD WATCH IS NOT CURRENTLY IN EFFECT, A FEW ISOLATED LOCATIONS COULD HAVE SMALLER STREAM FLOODING. ISOLATED AMOUNTS COULD REACH AS HIGH AS AROUND 4 INCHES. EXPECT FREQUENT LIGHTNING ALSO FROM THE STRONGER THUNDERSTORMS. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THE THREAT FOR MORE HEAVY RAIN AND POTENTIALLY STRONG THUNDERSTORMS WITH FREQUENT LIGHTNING EXISTS FOR MONDAY. IF ENOUGH SUNSHINE OCCURS, A FEW OF THE STORMS MIGHT REACH SEVERE LIMITS MONDAY. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE NEEDED. ANZ430-431-450>455-301000- 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- 400 AM EDT SUN JUL 29 2007 THIS HAZARDOUS WEATHER OUTLOOK IS FOR ATLANTIC COASTAL WATERS AND DELAWARE BAY WATERS. .DAY ONE...TODAY AND TONIGHT PLEASE BE WARY OF THE LIGHTNING THREAT FROM ANY THUNDERSTORMS THROUGH TONIGHT. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY PLEASE BE WARY OF THE LIGHTNING THREAT FROM THUNDERSTORMS ON MONDAY. IN ADDITION A COUPLE OF STORMS COULD REACH SPECIAL MARINE WARNING WIND CRITERIA. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION MAY BE NEEDED. TFG
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 310 AM EDT SUN JUL 29 2007 PAZ060-290915- BERKS- 310 AM EDT SUN JUL 29 2007 ...A STRONG THUNDERSTORM WILL AFFECT BERKS COUNTY... AT 306 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A STRONG THUNDERSTORM 16 MILES WEST OF READING...MOVING NORTHEAST AT 15 MPH. THE THUNDERSTORM WILL BE NEAR WOMELSDORF...ROBESONIA AROUND 315 AM...BERNVILLE...SINKING SPRING AROUND 330 AM...WYOMISSING...WEST READING AROUND 345 AM...CENTERPORT...LEESPORT AROUND 400 AM...HAMBURG AND SHOEMAKERSVILLE AROUND 415 AM. VERY HEAVY RAIN WILL FALL FROM THIS STORM...AND WILL CAUSE WATER TO POND ON ROADS AND QUICKLY FILL ROADSIDE DITCHES AND SMALL STREAMS. TAKE ROADS THAT ARE NOT PRONE TO FLOODING. EXPECT INTENSE LIGHTNING FROM THIS STORM. TFG
The national radar mosaic for the moment the first event began.
2 thunderstorm wind. Local standard time, as filed.
A severe thunderstorm knocked down a few trees in Penn Township.
Several trees were knocked down by a severe thunderstorm in Coplay Borough.
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: 52451, 52452.