A cold front slowly approaching from New York State helped trigger some severe thunderstorms during the evening of the 20th in Pennsylvania.
Every event with a place to put it. Tap one for its entry below.
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 cold front slowly approaching from New York State helped trigger some severe thunderstorms during the evening of the 20th in 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 20, 3:20 PM EST, 3 hours 45 minutes earlier.
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
420 PM EDT SUN JUL 20 2008
.SYNOPSIS...
TROPICAL STORM CRISTOBAL IS EXPECTED TO PASS WELL TO OUR SOUTHEAST
AND EAST ON MONDAY AND MONDAY NIGHT. MEANWHILE, A FRONTAL BOUNDARY
WILL DROP DOWN FROM THE NORTHWEST AND IT SHOULD REACH EASTERN
PENNSYLVANIA, NEW JERSEY, NORTHEASTERN MARYLAND AND DELAWARE ON
MONDAY. THE BOUNDARY IS FORECAST TO STALL OVER OUR REGION FOR MUCH
OF THE NEW WEEK. IT MAY DISSIPATE TOWARD THE END OF THE WEEK, THEN
ANOTHER FRONTAL BOUNDARY IS ANTICIPATED TO DROP DOWN FROM THE
NORTHWEST FOR NEXT WEEKEND.
&&
.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
WITH A GOOD AMOUNT OF SUNSHINE, TEMPERATURES ROSE INTO THE LOWER AND
MIDDLE 90S THROUGHOUT MUCH OF OUR FORECAST AREA THIS AFTERNOON.
SOME DRIER AIR BEGAN TO MIX DOWN FROM ALOFT AND INTO THE
PHILADELPHIA METROPOLITAN AREA AND POINTS TO THE NORTH AT MID
AFTERNOON. DEW POINT TEMPERATURES BEGAN TO DROP INTO THE LOWER AND
MIDDLE 60S IN SPOTS. NEVERTHELESS, WE HAVE DECIDED TO KEEP THE
EXCESSIVE HEAT WARNING IN EFFECT UNTIL 800 PM.
ISOLATED SHOWERS AND THUNDERSTORMS DEVELOPED OVER DELAWARE BAY AND
SOUTHEASTERN NEW JERSEY DURING THE AFTERNOON. THE REMAINDER OF OUR
FORECAST AREA REMAINED PRECIPITATION FREE. IT LOOKS AS THOUGH NOT
MUCH WILL CHANCE INTO THE VERY EARLY EVENING HOURS.
WE WILL BE LOOKING TO THE WEST, AS SHOWERS AND THUNDERSTORMS
APPROACH FROM THAT DIRECTION. IT APPEARS AS THOUGH THE LEADING EDGE
OF THE PRECIPITATION WILL REACH WESTERN BERKS COUNTY AROUND 730 PM.
THE SHOWERS AND THUNDERSTORMS SHOULD MOVE ACROSS MAINLY THE NORTHERN
AND CENTRAL PARTS OF OUR FORECAST AREA DURING THE FIRST PART OF THE
NIGHTTIME PERIOD. SOME PRECIPITATION MAY LINGER BEYOND MIDNIGHT IN
SPOTS, SO WE DID NOT LIMIT THE MENTION OF RAIN TO JUST THE EVENING
HOURS.
&&
.SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/...
FOR THE LATEST INFORMATION REGARDING TROPICAL STORM CRISTOBAL,
PLEASE REFER TO THE LATEST STATEMENTS FROM THE NATIONAL HURRICANE
CENTER.
DURING THE SHORT TERM PERIOD, THE UPPER FLOW WILL BEGIN AS ZONAL,
WITH A TROUGH EVENTUALLY BEGINNING TO DIG OVER THE GREAT LAKES AND
NORTHEAST, AS A RIDGE BEGINS TO BUILD OVER THE GREAT PLAINS.
A FRONTAL BOUNDARY FROM THE NORTHWEST IS EXPECTED TO DROP INTO OUR
REGION FROM THE NORTHWEST ON MONDAY. WHILE IT WILL REMAIN QUITE
WARM, A WESTERLY WIND SHOULD HELP TO MIX DOWN SOME DRIER AIR DURING
THE AFTERNOON HOURS, CAUSING DEW POINT TEMPERATURES TO DROP INTO THE
LOWER AND MIDDLE 60S. AS A RESULT, HEAT INDEX VALUES SHOULD ONLY
REACH THE MIDDLE 90S IN THE PHILADELPHIA METROPOLITAN AREA.
THEREFORE, WE WILL NOT NEED TO EXTEND THE EXCESSIVE HEAT WARNING.
EVEN WITH THE FRONTAL BOUNDARY IN THE REGION, IT APPEARS AS THOUGH
ANY SHOWERS AND THUNDERSTORMS ON MONDAY AFTERNOON AND EVENING WILL
BE ISOLATED. AS A RESULT, WE HAVE NOT MENTIONED THEM IN THE
FORECAST AT THIS TIME.
THE WEATHER SHOULD REMAIN RATHER QUIET FROM MONDAY NIGHT INTO EARLY
TUESDAY.
A WEAK WAVE OF LOW PRESSURE MAY RIDE ALONG THE FRONTAL BOUNDARY ON
TUESDAY NIGHT AND WEDNESDAY, INCREASING THE CHANCES FOR SHOWERS AND
THUNDERSTORMS. WITH THE POTENTIAL FOR A LITTLE MORE CLOUD COVER
EACH DAY, A SLIGHT COOLING TREND IS EXPECTED FOR TUESDAY AND
WEDNESDAY.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
THE UPPER PATTERN FEATURING A TROUGH OVER THE EAST WITH A RIDGE OVER
THE WEST SHOULD REMAIN IN PLACE DURING THE LONG TERM PERIOD OF THE
FORECAST, HELPING TO PREVENT THE DEVELOPMENT OF ANOTHER HEAT WAVE.
PRECIPITATION ASSOCIATED WITH THE FRONTAL BOUNDARY AND THE PASSING
WAVE OF LOW PRESSURE ARE EXPECTED TO LINGER INTO WEDNESDAY NIGHT.
EVEN THOUGH THE FRONTAL BOUNDARY IS EXPECTED TO LINGER OVER OR NEAR
THE REGION FOR THURSDAY AND FRIDAY, IT SHOULD BEGIN TO DISSIPATE.
ISOLATED SHOWERS AND THUNDERSTORMS ARE NOT OUT OF THE QUESTION,
ESPECIALLY ON THE COASTAL PLAIN. FOR THE MOST PART, WE WILL LEAVE
THEM OUT OF THE FORECAST FOR NOW.
ANOTHER FRONT IS EXPECTED TO DROP DOWN FROM THE NORTHWEST, WITH
INCREASING CHANCES FOR PRECIPITATION ON FRIDAY NIGHT AND SATURDAY.
&&
.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
HIGH PRESSURE WILL REMAIN OVER THE REGION EARLY IN THE PERIOD AND
VFR CONDITIONS ARE EXPECTED. THERE WILL BE SOME ISOLATED TO
SCATTERED EVENING THUNDERSTORMS THAT COULD REDUCE VSBYS AND CIGS TO
IFR/MVFR. HOWEVER, WILL NOT MENTION IN INDIVIDUAL TAF SITES AS IT
IS DIFFICULT TO TIME AND LOCATE THE DIURNAL CONVECTION. WILL
CONTINUE TO MENTION CB. A COLD FRONT WILL APPROACH THE AREA ON
MONDAY THEN STALL INVOF THE REGION. THERE WILL BE SOME ADDITIONAL
ISOLD TSRAS ON MONDAY AS WELL, BUT AGAIN WILL NOT MENTION AT
INDIVIDUAL SITES DUE TO RELATIVELY SMALL AREAL COVERAGE.
OUTLOOK...
THE COLD FRONT THAT STALLS NEAR THE AREA MAY ACT AS A TRIGGER FOR
DIURNAL TSRA THROUGH MIDWEEK. THERE COULD BE ADDITIONAL CIG/VSBY
RESTRICTIONS WITH ANY TSRA.
&&
.MARINE...
AT THE BEGINNING OF THE PD, HIGH PRESSURE WILL BE IN CONTROL.
HOWEVER, SEVERAL FEATURES WILL AFFECT THE MARINE AREA THROUGH
MIDWEEK. SWELLS FROM BERTHA WILL CONTINUE TO DECREASE AS THE SYS
MOVES FURTHER AWAY IN THE OPEN ATLC.
HOWEVER, AS T.S. CRISTOBAL MOVES NEWD, SWELLS WILL INCREASE BY
MONDAY AND CONTINUE INTO MIDWEEK. AT THE SAME TIME, A COLD FRONT
WILL MOVE ACROSS THE REGION ON MONDAY AND THEN STALL INVOF THE AREA.
WAVEWATCH HAS REALLY INCREASED SEAS AS A RESULT OF INCREASING SWLY
FLOW AHEAD OF A LOW PRES SYS. HOWEVER, THE GFS AND WAVEWATCH APPEAR
TO BE OVERDONE WITH THIS AS THE GFS IS CLEARLY SUFFERING SOME
FEEDBACK PROBLEMS. SO, WILL INCREASE SEAS A BIT, BUT NOT NEARLY AS
MUCH AS THE GFS. CURRENT FCST WINDS DO NOT SUPPORT SEAS AS HIGH AS
THE GFS INDICATES. ADDITIONALLY, CRISTOBALS AFFECT ON THE REGION
SHOULD BE LONG PAST AT THAT TIME.
RIP CURRENTS...
SWELLS ARE EXPECTED TO REDEVELOP A LONGER PERIOD AGAIN IN RESPONSE
TO TROPICAL STORM CRISTOBAL, WHICH WAS EAST OF THE CAROLINA COAST.
CRISTOBAL IS EXPECTED TO HEAD TOWARD THE NORTHEAST AND WELL EAST OF
THE NEW JERSEY AND DELAWARE COASTS MONDAY NIGHT. THIS MAY BRING A
CONSEQUENT INCREASE IN THE RIP CURRENT RISK TO THE AREA.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...EXCESSIVE HEAT WARNING UNTIL 8 PM EDT THIS EVENING FOR
PAZ067>071.
NJ...EXCESSIVE HEAT WARNING UNTIL 8 PM EDT THIS EVENING FOR NJZ015-
017>019.
DE...EXCESSIVE HEAT WARNING UNTIL 8 PM EDT THIS EVENING FOR DEZ001.
MD...NONE.
MARINE...NONE.
&&
SYNOPSIS/NEAR TERM/SHORT TERM/LONG TERM...IOVINO
AVIATION/MARINE...NIERENBERGHAZARDOUS WEATHER OUTLOOK...UPDATED NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 345 PM EDT SUN JUL 20 2008 DEZ001-NJZ015-017>019-PAZ067>071-211100- NEW CASTLE-MERCER-GLOUCESTER-CAMDEN-NORTHWESTERN BURLINGTON-CHESTER- MONTGOMERY-BUCKS-DELAWARE-PHILADELPHIA- 345 PM EDT SUN JUL 20 2008 ...EXCESSIVE HEAT WARNING IN EFFECT UNTIL 8 PM EDT THIS EVENING... THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHERN DELAWARE...CENTRAL NEW JERSEY...SOUTHERN NEW JERSEY AND SOUTHEAST PENNSYLVANIA. .DAY ONE...THIS AFTERNOON AND TONIGHT PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV ON THE INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS. EXCESSIVE HEAT WARNING. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY MONDAY WILL BE A DAY THAT OFFERS ONLY MODEST RELIEF FROM THE HEAT, AS TEMPERATURES STILL ARE EXPECTED TO REACH THE 90 DEGREE MARK. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME. NJZ001-007>010-PAZ054-055-060>062-211100- SUSSEX-WARREN-MORRIS-HUNTERDON-SOMERSET-CARBON-MONROE-BERKS-LEHIGH- NORTHAMPTON- 345 PM EDT SUN JUL 20 2008 THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHERN NEW JERSEY...NORTHWEST NEW JERSEY...EAST CENTRAL PENNSYLVANIA AND NORTHEAST PENNSYLVANIA. .DAY ONE...THIS AFTERNOON AND TONIGHT THE STORM PREDICTION CENTER HAS PLACED THE AREA UNDER A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING. DAMAGING WINDS AND LARGE HAIL ARE THE MAIN THREATS. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME. DEZ002-003-MDZ008-012-015-019-020-NJZ012-013-016-020>023-027-211100- KENT-INLAND SUSSEX-CECIL-KENT MD-QUEEN ANNES-TALBOT-CAROLINE- MIDDLESEX-WESTERN MONMOUTH-SALEM-OCEAN-CUMBERLAND-ATLANTIC-CAPE MAY- SOUTHEASTERN BURLINGTON- 345 PM EDT SUN JUL 20 2008 THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL DELAWARE...SOUTHERN DELAWARE...NORTHEAST MARYLAND...CENTRAL NEW JERSEY...NORTHERN NEW JERSEY AND SOUTHERN NEW JERSEY. .DAY ONE...THIS AFTERNOON AND TONIGHT NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME. DEZ004-NJZ014-024>026-211100- DELAWARE BEACHES-EASTERN MONMOUTH-ATLANTIC COASTAL CAPE MAY- COASTAL ATLANTIC-COASTAL OCEAN- 345 PM EDT SUN JUL 20 2008 THIS HAZARDOUS WEATHER OUTLOOK IS FOR SOUTHERN DELAWARE...CENTRAL NEW JERSEY AND SOUTHERN NEW JERSEY. .DAY ONE...THIS AFTERNOON AND TONIGHT NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY THERE MAY BE A MODERATE THREAT OF RIP CURRENTS DURING THE EARLY TO MIDDLE PART OF THE NEW WEEK DUE TO LONG PERIOD SWELLS FROM CRISTOBAL. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME. ANZ430-431-450>455-211100- 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- 345 PM EDT SUN JUL 20 2008 THIS HAZARDOUS WEATHER OUTLOOK IS FOR ATLANTIC COASTAL WATERS AND DELAWARE BAY WATERS. .DAY ONE...THIS AFTERNOON AND TONIGHT NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 414 PM EDT SUN JUL 20 2008 DEZ001-MDZ008-NJZ007-009-PAZ054-055-060>062-067>071-210215- NEW CASTLE-CECIL-WARREN-HUNTERDON-CARBON-MONROE-BERKS-LEHIGH- NORTHAMPTON-CHESTER-MONTGOMERY-BUCKS-DELAWARE-PHILADELPHIA- INCLUDING THE CITIES OF...WILMINGTON...ELKTON...WASHINGTON... FLEMINGTON...JIM THORPE...STROUDSBURG...READING...ALLENTOWN... BETHLEHEM...EASTON...WEST CHESTER...NORRISTOWN...DOYLESTOWN... MEDIA...PHILADELPHIA 414 PM EDT SUN JUL 20 2008 ...A CHANCE OF THUNDERSTORMS...SOME SEVERE THIS EVENING... THERE HAVE BE SOME WIDELY SCATTERED THUNDERSTORMS, BUT A MORE MORE AGGRESSIVE LINE OF STORMS WAS MOVING INTO CENTRAL PENNSYLVANIA. THIS LINE IS MOVING TO THE EAST AT 30 TO 35 MPH. A GOOD PART OF THE REGION, NORTH OF THE DELAWARE VALLEY, IS IN A RISK OF SEVERE THUNDERSTORMS. TEMPERATURES REMAIN IN THE 90S ACROSS THE AREA AND THE ATMOSPHERE IS BECOMING VERY UNSTABLE AHEAD OF THE ADVANCING LINE. THE AREAS MOST LIKELY TO BE AFFECTED FIRST WILL BE THE SOUTHERN LEHIGH VALLEY BY 730 PM AND THEN THE STORMS WILL CONTINUE TO SPREAD EAST AND REACH, NORTHEAST MARYLAND, NORTHERN DELAWARE AND WESTERN NEW JERSEY BEFORE 9 PM. PLEASE STAY TUNED FOR ADDITIONAL STATEMENTS AND POSSIBLY WARNINGS THAT COULD BE ISSUED AS WE APPROACH SUNDOWN. EBERWINE
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 613 PM EDT SUN JUL 20 2008 NJZ001-007-PAZ054-055-060>062-068-202315- BERKS PA-CARBON PA-LEHIGH PA-MONROE PA-MONTGOMERY PA-NORTHAMPTON PA- SUSSEX NJ-WARREN NJ- 613 PM EDT SUN JUL 20 2008 ...STRONG THUNDERSTORMS WILL AFFECT BERKS...CARBON...LEHIGH... MONROE...MONTGOMERY...NORTHAMPTON...SUSSEX AND WARREN COUNTIES... AT 610 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED STRONG THUNDERSTORMS 55 MILES NORTHWEST OF LANCASTER...MOVING EAST AT 41 MPH. THE THUNDERSTORMS WILL BE NEAR STRAUSSTOWN AND CENTERPORT AROUND 700 PM. VERY HEAVY RAIN WILL FALL FROM THIS STORM...AND WILL CAUSE WATER TO POND ON ROADS AND QUICKLY FILL ROADSIDE DITCHES AND SMALL STREAMS. WIND GUSTS TO 50 MPH ARE POSSIBLE WITH THESE STORMS. EXPECT FREQUENT LIGHTNING FROM THESE STORMS. DO NOT SEEK SHELTER UNDER TREES WHEN LIGHTNING THREATENS...MOVE INDOORS WHEN A THUNDERSTORM APPROACHES. EBERWINE
The Philadelphia radar (KDIX), 137 km away, was scanning. The volume nearest the first event began at 00:04 UTC.
5 thunderstorm wind, 1 lightning. Local standard time, as filed.
A severe thunderstorm tore down a couple of trees and poles in Cumru Township. Lightning strikes caused about 3,000 homes and businesses to lose power in Boyertown, Reading and Wyomissing.
A severe thunderstorm tore down some large tree limbs and wires in Whitehall Township. Pea size hail fell in Allentown from the same thunderstorm.
A series of severe thunderstorms tore several trees, tree limbs and wires across the central tier of Chester County.
A wind gust to 67 mph was measured in Forks Township. A very large tree was knocked down within the township.
A barn caught fire after a lightning strike on Devyn Drive in West Pikeland Township. The fire was contained to the barn and two nearby homes were undamaged. The historic barn though was a total loss. Six fire companies assisted in battling the blaze.
A severe thunderstorm tore down a couple of trees, tree limbs and wires in the northwestern part of Delaware County.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Pennsylvania in 2008Every state in 2008This day in weather historyWarnings in Pennsylvania, July 2008
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: 124452, 124453, 124454, 124457, 128173, 124456.