Locally heavy rainfall in a short duration associated with slow moving thunderstorms produced flash flooding across portions of the Lower Susquehanna Valley.
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 CTP wrote it up.
Locally heavy rainfall in a short duration associated with slow moving thunderstorms produced flash flooding across portions of the Lower Susquehanna Valley.
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 State College, PA wrote its last area forecast discussion before the first event at Aug 2, 6:49 AM EST, 2 hours 41 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 749 AM EDT SUN AUG 2 2009 .SYNOPSIS... A NEARLY STATIONARY UPPER LOW PRESSURE SYSTEM WILL REMAIN IN THE VICINITY OF HUDSON BAY FOR THE NEXT WEEK. DISTURBANCES ROTATING AROUND THIS SYSTEM WILL PUSH A WEAK COLD FRONT THROUGH PENNSYLVANIA ON SUNDAY. A STRONGER COLD FRONT WILL LIKELY PUSH THROUGH THE REGION LATE TUESDAY OR WEDNESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... FOCUS OF THE NEAR TERM FCST WILL BE POTENTIAL OF FLASH FLOODING ACROSS THE SOUTHEAST PORTION OF THE CWA. SLOW MOVING COLD FNTL BNDRY WILL PUSH INTO THE REGION TDY AHEAD OF SHORTWAVE ROTATING THRU THE GRT LKS. REGIONAL RADAR MOSAIC CURRENTLY SHOWING HEAVY SHRA/TSRA UPSTREAM OVR KENTUCKY AND WEST VIRGINIA. THIS AREA OF PRECIP APPEARS TO BE ASSOCIATED WITH WEAK WAVE OF LO PRES ALONG FRONT. EXPECT STRONG MOISTURE FLUX AHEAD OF THIS FEATURE TO TRANSLATE ENE INTO SOUTHEAST PA LATER TODAY...RESULTING IN LOCALLY HVY CONVECTIVE RAINFALL. LATEST BLENDED SATELLITE DATA SHOWING PWAT VALUES ARND 2 INCHES ALONG AND SOUTH OF THE LOW TRACK. PORTIONS OF THE SUSQ VALLEY REMAIN WET FROM RECENT RAINFALL AND SUSCEPTIBLE TO FLASH FLOODING. THUS...HAVE ISSUED FFA THRU EARLY EVENING IN COLLABORATION WITH ADJACENT OFFICES. WILL ALSO HAVE TO WATCH FOR POTENTIAL OF SVR WX LATER TODAY ACROSS SOUTHEAST PA. DIURNAL HEATING/DESTABILIZATION SOUTH OF WEAK SFC LOW TRACK...COMBINED WITH INCREASINGLY DEEP LYR SHEAR...COULD SUPPORT SUPERCELL POTENTIAL. LATEST RUC13 DATA PUSHING CAPES TO NR 2000J/KG BY 16Z ACROSS SE YORK/LANCASTER COUNTIES. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... THE CLD FNT SHOULD BE PRESSING EAST OF THE SUSQ VALLEY BY THIS EVENING...SO HAVE TAPERED THE POPS OFF FROM WEST TO EAST BTWN 21Z AND 03Z. CLEARING SKIES...LGT WIND AND RECENT RAINFALL LIKELY TO YIELD AREAS OF FOG LATE TONIGHT. LATEST ENSEMBLE DATA CONTINUES TO SUPPORT FAIR/SEASONABLE CONDS MONDAY...AS HI PRES RIDGE WORKS INTO THE AREA. ENOUGH MOISTURE MAY LINGER IN VICINITY OF STALLED FRONTAL BOUNDARY ALONG THE MID ATLANTIC COAST TO SUPPORT A SLGT CHC OF DIURNAL CONVECTION OVR LANCASTER COUNTY MON AFTN. ENS MEAN 850 TEMPS NR 15C SUGGEST HIGHS WILL RANGE FROM THE UPPER 70S ALLEGHENY MTNS...TO M80S SUSQ VALLEY. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... THE OVERALL PATTERN APPEARS TO KEEP A BROAD MID LVL TROUGH ACROSS THE CANADIAN PRAIRIES STRETCHING SOUTH THROUGH THE NORTHERN PLAINS AND WESTERN GREAT LAKES...DRIFTING EAST TOWARDS THE MIDDLE OF NEXT WEEK. ENSEMBLE MEMBERS BEGIN TO DIVERGE TOWARDS THE LATER PERIODS OF THE EXTENDED...WHICH SUGGESTS A LOWER CONFIDENCE AS THE PATTERN MAY BEGIN TO CHANGE TOWARDS MORE SEASONAL CONDS. TUE WILL FEATURE A WARM SURGE...AS A DECENT 850MB THERMAL RIDGE RIDES ALONG LEE-SIDE OF APPALACHIANS AT 17 TO 19 DEG C...SUGGESTING HIGHS NR 90F POSSIBLE ACROSS THE SUSQ VALLEY. THE WILDCARD WITH TEMPS THIS WARM WILL BE FLOW AND MOISTURE...WHICH APPEARS ATTM TO BE LGT WESTERLY/SOUTHWESTERLY SUPPORTING A DOWNSLOPING EFFECT FOR LOWER SUSQ-VALLEY LOCATIONS TUE AFTN. COLD FRONT IS PRESENTLY POISED TO PUSH THRU THE REGION TUES NITE. BEST DYNAMICS SHUD PASS TO OUR NORTH WITH CURRENT TRACK OF SHORTWAVE IN 500MB TROUGH...SO HAVE HIT POPS HARDEST ACROSS THE NW MTNS TUE AFTN AND TUE NITE. ENSEMBLE MEMBERS SUPPRESS INSTABILITY WED AFTN TO THE SOUTH...HOWEVER WITH MUCH COOLER AIR ALOFT CAN/T RULE OUT AN AFTN LOW TOPPED SHRA/TSRA. BROAD SFC RIDGE IS SUPPORTED BY GEFS TO CLOSE OUT THE WEEK...THUR/FRI SHUD PRIMARILY BE DRY. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... AS EXPECTED...SOME LOWER CU/SC MOVING IN...ALONG WITH A SHOWER OR TWO. HOWEVER...DID NOT EXPECT A TRUCK LOAD OF POTENTIAL FLASH FLOODING STORMS ACROSS THE SOUTH CENTRAL PART OF THE STATE. SO FAR THINGS ARE MOVING...HAVE SEEN THESE SETUPS BEFORE DUMP OVER 4 INCHES OF RAIN...AS RIDGE DANCER STORMS TEND TO FLARE UP AT NIGHT. IN THIS CASE...STORMS FIRING ON EDGE OF 70 DEGREE DEWPOINTS. THINK CLUE WAS THE SHEAR I SAW ON THE TCU THIS AFT. LUCKY WINDS ARE NOT SE AT LOW LEVELS...WOULD HAVE OTHER THINGS TO BE CONCERN ABOUT...GIVEN MAINLY WESTERLY VAD WINDS ABOVE 10000 FEET. ANYWAY...THIS ACTIVITY WILL BE REPLACED BY MORE IN THE WAY OF WIDESPREAD SHOWER ACTIVITY...ALONG WITH ISOLATED STORMS LATER THIS MORNING INTO THIS AFT. SKIES SHOULD CLEAR FROM WEST TO EAST BY LATE AFT. THUS A WIDE RANGE OF CONDITIONS TODAY...BECOMING VFR BY LATE AFT. HOWEVER...EXPECT FOG TO FORM BY LATE EVENING...GIVEN HOW MOIST THINGS HAVE BEEN LATELY. NOT A BAD DAY ON MONDAY. ANOTHER FRONT FOR TUE. OUTLOOK... MON...AM FOG...THEN VFR. TUE...MAINLY VFR. SCT MVFR IN SHRA/TSRA MAINLY N/W AHEAD OF CLD FNT. WED...VFR. SHOWERS PSBL EARLY...MAINLY IN THE S/E WITH LOCAL CIG/VSBY RESTRICTIONS. THU...VFR. && .CLIMATE... THE AVERAGE TEMPERATURE LAST MONTH AT HARRISBURG WAS /73.0/ DEGREES OR (-2.9) DEGREES BELOW NORMAL. THIS TIES JULY 1920 AS THE NINTH COLDEST ON RECORD. THE AVERAGE TEMPERATURE LAST MONTH AT WILLIAMSPORT WAS /70.0/ DEGREES OR (-2.4) DEGREES BELOW NORMAL. THIS MAKES JULY 2009 THE FIFTH COLDEST ON RECORD. && .CTP WATCHES/WARNINGS/ADVISORIES... FLASH FLOOD WATCH THROUGH THIS EVENING FOR PAZ026>028-034>036- 042-046-049>053-056>059-063>066. && SYNOPSIS...FITZGERALD NEAR TERM...FITZGERALD SHORT TERM...FITZGERALD LONG TERM...FITZGERALD/BEACHLER AVIATION...MARTIN/RXR CLIMATE...STEINBUGL
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE STATE COLLEGE PA 512 AM EDT SUN AUG 2 2009 PAZ004>006-010>012-017>019-024-025-033-037-041-045-030915- WARREN-MCKEAN-POTTER-ELK-CAMERON-NORTHERN CLINTON-CLEARFIELD- NORTHERN CENTRE-SOUTHERN CENTRE-CAMBRIA-BLAIR-SOMERSET-TIOGA- NORTHERN LYCOMING-SOUTHERN CLINTON- 512 AM EDT SUN AUG 2 2009 THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL PENNSYLVANIA. .DAY ONE...TODAY AND TONIGHT. THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY. THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME. PAZ026>028-034>036-042-046-049>053-056>059-063-064-030915- HUNTINGDON-MIFFLIN-JUNIATA-BEDFORD-FULTON-FRANKLIN-SULLIVAN- SOUTHERN LYCOMING-UNION-SNYDER-MONTOUR-NORTHUMBERLAND-COLUMBIA-PERRY- DAUPHIN-SCHUYLKILL-LEBANON-CUMBERLAND-ADAMS- 512 AM EDT SUN AUG 2 2009 ...FLASH FLOOD WATCH IN EFFECT THROUGH THIS EVENING... THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL PENNSYLVANIA. .DAY ONE...TODAY AND TONIGHT. PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV/STATECOLLEGE ON THE INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS. FLASH FLOOD WATCH. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY. THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME. PAZ065-066-030915- YORK-LANCASTER- 512 AM EDT SUN AUG 2 2009 ...FLASH FLOOD WATCH IN EFFECT THROUGH THIS EVENING... THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL PENNSYLVANIA. .DAY ONE...TODAY AND TONIGHT. PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV/STATECOLLEGE ON THE INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS. WIDESPREAD SHOWERS AND THUNDERSTORMS WILL AFFECT THE AREA TODAY AHEAD OF AN APPROACHING FRONTAL BOUNDARY. THERE IS A SLIGHT CHANCE THAT A FEW OF THE THUNDERSTORMS COULD PRODUCE DAMAGING WIND GUSTS OR LARGE HAIL THIS AFTERNOON. FLASH FLOOD WATCH. .DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY. THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
508 AM EDT SUN AUG 2 2009
PAZ065-066-021000-
LANCASTER PA-YORK PA-
508 AM EDT SUN AUG 2 2009
...A STRONG THUNDERSTORM WILL AFFECT LANCASTER AND SOUTHEASTERN YORK
COUNTIES...
AT 505 AM EDT...A STRONG THUNDERSTORM WAS LOCATED 3 MILES EAST OF
WILLOW STREET...MOVING NORTHEAST AT 35 MPH. OTHER STORMS WERE
DEVELOPING OVER NORTHERN MARYLAND..AND WILL CONTINUE TO MOVE
ACROSS SOUTHEAST YORK AND LANCASTER COUNTIES.
WIND GUSTS TO 40 MPH AND SMALL HAIL ARE POSSIBLE WITH THIS STORM.
THIS STORM WILL BE NEAR PARADISE AROUND 510 AM...LEOLA AROUND 515
AM...NEW HOLLAND AROUND 520 AM...REAMSTOWN AROUND 525 AM...TERRE HILL
AROUND 530 AM AND CHURCHTOWN AROUND 535 AM.
THIS WILL IMPACT THE FOLLOWING CENTRAL PENNSYLVANIA INTERSTATES...THE
PENNSYLVANIA TURNPIKE BETWEEN MILE MARKERS 276 AND 295...I-83 BETWEEN
MILE MARKERS 1 AND 13.
THIS WILL ALSO IMPACT THE FOLLOWING MAJOR ROADS...STATE HIGHWAY
283...ROUTE 30...ROUTE 222...ROUTE 322...STATE ROAD 41...STATE ROAD
501.
LAT...LON 4031 7617 4032 7614 4015 7589 4011 7593
4005 7594 3992 7600 3987 7599 3973 7611
3971 7630 3972 7694
EXPERIMENTAL
FORECASTER: MARTINSPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE STATE COLLEGE PA 708 AM EDT SUN AUG 2 2009 PAZ064-065-021200- ADAMS PA-YORK PA- 708 AM EDT SUN AUG 2 2009 ...A STRONG THUNDERSTORM WILL AFFECT SOUTHERN ADAMS AND SOUTHWESTERN YORK COUNTIES... AT 706 AM EDT...A STRONG THUNDERSTORM WAS LOCATED 6 MILES EAST OF HAGERSTOWN...MOVING NORTHEAST AT 30 MPH. WIND GUSTS TO 40 MPH AND SMALL HAIL ARE POSSIBLE WITH THIS STORM. THIS STORM WILL BE NEAR CARROLL VALLEY AROUND 735 AM...GETTYSBURG AROUND 755 AM AND BONNEAUVILLE AROUND 800 AM. THIS WILL IMPACT THE FOLLOWING MAJOR ROADS...ROUTE 15...ROUTE 30... STATE ROAD 94...STATE ROAD 97. LAT...LON 3974 7747 4000 7684 3972 7674 3972 7747 EXPERIMENTAL FORECASTER: MARTIN
SPECIAL WEATHER STATEMENT NATIONAL WEATHER SERVICE STATE COLLEGE PA 818 AM EDT SUN AUG 2 2009 PAZ066-021245- LANCASTER PA- 818 AM EDT SUN AUG 2 2009 ...A STRONG THUNDERSTORM WILL AFFECT NORTHEASTERN LANCASTER COUNTY... AT 817 AM EDT...A STRONG THUNDERSTORM WAS LOCATED OVER LANCASTER... MOVING NORTHEAST AT 40 MPH. WIND GUSTS TO 40 MPH AND SMALL HAIL ARE POSSIBLE WITH THIS STORM. THIS STORM WILL BE NEAR LEOLA AROUND 825 AM...NEW HOLLAND AROUND 830 AM...TERRE HILL AROUND 835 AM AND ADAMSTOWN AROUND 840 AM. THIS WILL IMPACT THE PENNSYLVANIA TURNPIKE BETWEEN MILE MARKERS 283 AND 295. THIS WILL ALSO IMPACT THE FOLLOWING MAJOR ROADS...STATE HIGHWAY 283...ROUTE 30...ROUTE 222...ROUTE 322...STATE ROAD 501. LAT...LON 3995 7627 4004 7644 4028 7609 4015 7589 EXPERIMENTAL FORECASTER: STEINBUGL
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
953 AM EDT SUN AUG 2 2009
PAZ066-021430-
LANCASTER PA-
953 AM EDT SUN AUG 2 2009
...A STRONG THUNDERSTORM WILL AFFECT SOUTHEASTERN LANCASTER COUNTY...
AT 951 AM EDT...A STRONG THUNDERSTORM WAS LOCATED 13 MILES SOUTHEAST
OF WILLOW STREET...MOVING NORTHEAST AT 35 MPH.
WIND GUSTS TO 40 MPH AND SMALL HAIL ARE POSSIBLE WITH THIS STORM.
THIS STORM WILL BE NEAR STRASBURG AROUND 1000 AM...PARADISE AROUND
1005 AM AND CHRISTIANA AROUND 1010 AM.
THIS WILL IMPACT THE FOLLOWING MAJOR ROADS...ROUTE 30...ROUTE 222...
ROUTE 322...STATE ROAD 41.
ADDITIONAL STORMS ARE FORMING TO THE SOUTH OF THE STRONGEST STORM.
PERSONS ACROSS THE REGION SHOULD REMAIN ALERT FOR RAPID CHANGES
IN CONDITIONS.
LAT...LON 3979 7628 4001 7624 4015 7589 4014 7589
4011 7593 4005 7594 3992 7600 3987 7599
3985 7602 3978 7606 3973 7611 3972 7623
EXPERIMENTAL
FORECASTER: MARTINThe State College radar (KCCX), 153 km away, was scanning. The volume nearest the first event began at 14:28 UTC.
2 flash flood. Local standard time, as filed.
Locally heavy rainfall of 1-2 inches in a short duration produced flash flooding along Route 72 and Route 322 southbound near Cornwall.
Locally heavy rainfall of 1-2 inches in a short duration resulted in flash flooding across mainly rural areas in extreme southeastern Lancaster County. A mudslide closed one lane of Route 472 in Colerain Township near Mount Eden Road. Two feet of water was also reported covering Spruce Grove Road in Colerain Township.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Pennsylvania in 2009Every state in 2009This day in weather historyWarnings in Pennsylvania, August 2009
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: 177105, 176682.