S dragged a weak cold front over the Ohio Valley. This coldfront set off thunderstorms in the afternoon and evening hours on the 18th.
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 PBZ wrote it up.
A shortwave traveling north over a broad ridge in the central U.S dragged a weak cold front over the Ohio Valley. This coldfront set off thunderstorms in the afternoon and evening hours on the 18th. There were several reports of wind damage in eastern Ohio and western Pennsylvania with more than 11,000 people without power in western PA alone. In addition urban flooding and flash flooding occurred in various parts of Allegheny and Beaver counties. Cars were stranded in high water right around rush-hour on Washington Blvd in downtown Pittsburgh.
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 Pittsburgh, PA wrote its last area forecast discussion before the first event at Jul 18, 9:30 AM EST, 2 hours 35 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 1030 AM EDT MON JUL 18 2011 .SYNOPSIS... A WEAK COLD FRONT, MOVING SOUTHWARD FROM THE GREAT LAKES, CAN GENERATE SCATTERED THUNDERSTORMS THIS AFTERNOON AND TONIGHT. THIS FRONT WILL RETREAT NORTHWARD TUESDAY, AND SO HOT AND HUMID CONDITIONS CAN BE EXPECTED THE REST OF THE WEEK. && .NEAR TERM /THROUGH TONIGHT/... PER RECENT SATELLITE DATA, STRATUS WILL HAVE BURNED OFF BY 11 AM. HIGH CLOUDS AND DEVELOPING CUMULUS ARE EXPECTED TO ONLY PARTIALLY LIMIT SUNSHINE THE REST OF TODAY. PER RECENT WRF-NMM AND SREF MODEL OUTPUT, EXPECT PREFRONTAL SCATTERED THUNDERSTORMS TO DEVELOP SOUTHWARD OF THE GREAT LAKES THIS AFTERNOON AND EARLY TONIGHT, WHEN STORMS CAN BECOME MORE NUMEROUS. DUE TO HUMID SURFACE LAYER, THUNDERSTORMS CAN BE POWERED BY GREAT INSTABILITY. SURFACE FRONT AND SHORT-WAVE TROUGH ALOFT IN NORTHWEST FLOW WILL ORGANIZE THUNDERSTORM DEVELOPMENT ALSO, PERHAPS INTO SHORT-LINES. SO CONCUR WITH SPC REGARDING SLIGHT RISK OF SEVERE. WILL ALSO MONITOR FOR HEAVY RAINFALL. MADE SMALL ADJUSTMENTS TO FORECASTED TEMPERATURES BASED ON RECENT HRRR AND NAM AND SREF MODEL OUTPUT. SURFACE DEW POINTS IN THE UPPER 60S WILL UP APPARENT TEMPERATURES/HEAT INDEX VALUES/ INTO THE 90S. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY/... FORECAST OF PRECIP PROBABILITIES WAS TAPERED DOWNWARD LATER TONIGHT AND THROUGH TUESDAY DUE TO EXPECTED SOUTHWARD PROGRESS OF THE WEAK FRONT. GIVEN PROGGED BUILDING OF HIGH PRESSURE ON WEDNESDAY, HAVE ONLY FORECAST SLIGHT PRECIP NUMBERS WITH DIURNAL RESTRICTIONS IN THE RISING HEAT. HOT AND HUMID CONDITIONS WILL THUS PREVAIL WITH HEAT INDEX READINGS FORECAST IN THE UPPER 90S FOR AREAS SOUTHWEST OF PITTSBURGH ON WEDNESDAY AFTERNOON. MENTION OF THE HOT AND HUMID CONDITIONS WILL BE MAINTAINED IN THE HAZARDOUS WEATHER OUTLOOK. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... HOT, HUMID WEATHER WILL PERSIST INTO LATE WEEK AS STRONG UPPER RIDGE OVER THE MIDWEST IS PROJECTED TO SLIDE EASTWARD. WITH AMPLE LOW LEVEL MOISTURE IN PLACE, WILL KEEP AT LEAST A SLIGHT CHANCE OF DIURNAL THUNDERSTORMS IN THE FORECAST FOR EACH DAY THOUGH FRIDAY. A BETTER CHANCE OF PRECIPITATION EXISTS OVER THE WEEKEND AS A FRONTAL BOUNDARY PUSHES INTO THE GREAT LAKES. && .AVIATION /14Z MONDAY THROUGH FRIDAY/... PER RECENT SURFACE AND SATELLITE DATA, EXPECT CONTINUED IMPROVEMENT IN FLIGHT CONDITIONS TO MVFR ABOUT 15Z AND VFR 16Z-17Z AS STRATUS CLOUDS LIFT AND FOG DISSIPATES, AND VFR CUMULUS DEVELOPS. A COLD FRONT WILL PUSH SOUTHWARD TOWARD THE REGION LATE THIS AFTERNOON INTO THE EVENING HOURS. THIS FEATURE WILL PROVIDE A FOCUS FOR SCATTERED THUNDERSTORMS AND THE POTENTIAL FOR RESTRICTIONS. WITH MESOSCALE MODELS INCREASING CONFIDENCE, TEMPO GROUPS FOR TSRA WITH MVFR RESTRICTIONS WERE INCLUDED IN TAFS FOR THIS EVENING EVERYWHERE EXCEPT KMGW. IT IS POSSIBLE THAT A FEW OF STORMS MAY BE SEVERE WITH A THREAT OF GUSTY WINDS. THE CHANCE OF SHOWERS AND STORMS WILL CONTINUE THROUGH MOST OF THE OVERNIGHT PERIOD WITH A WARM AND HUMID AIR MASS IN PLACE. OUTLOOK /TUESDAY THROUGH FRIDAY/... MVFR RESTRICTIONS IN HAZE WILL BE POSSIBLE AT TIMES TUESDAY THROUGH FRIDAY AS A HOT AND HUMID AIR MASS BUILDS INTO THE REGION. RESTRICTIONS ARE ALSO POSSIBLE IN PATCHY EARLY MORNING FOG AND WIDELY SCATTERED AFTERNOON AND EVENING THUNDERSTORMS. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. &&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE PITTSBURGH PA 414 AM EDT MON JUL 18 2011 MDZ001-OHZ039>041-048>050-057>059-068-069-PAZ007>009-013>016-020>023- 029-031-073>076-WVZ001>004-012-021>023-041-190815- GARRETT-TUSCARAWAS-CARROLL-COLUMBIANA-COSHOCTON-HARRISON- JEFFERSON OH-MUSKINGUM-GUERNSEY-BELMONT-NOBLE-MONROE-MERCER-VENANGO- FOREST-LAWRENCE-BUTLER-CLARION-JEFFERSON PA-BEAVER-ALLEGHENY- ARMSTRONG-INDIANA-WASHINGTON-GREENE-WESTMORELAND-WESTMORELAND RIDGES- FAYETTE-FAYETTE RIDGES-HANCOCK-BROOKE-OHIO-MARSHALL-WETZEL-MARION- MONONGALIA-PRESTON-TUCKER- 414 AM EDT MON JUL 18 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN MARYLAND...EAST CENTRAL OHIO...NORTHWEST PENNSYLVANIA...SOUTHWEST PENNSYLVANIA...WEST CENTRAL PENNSYLVANIA...NORTHERN WEST VIRGINIA AND NORTHERN PANHANDLE OF WEST VIRGINIA. .DAY ONE...TODAY AND TONIGHT. THERE IS A CHANCE FOR SEVERE THUNDERSTORMS TODAY WITH THE PRIMARY THREATS COMING FROM DAMAGING WIND AND LARGE HAIL. .DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY. STRONG HIGH PRESSURE IS PROJECTED TO BUILD ACROSS THE REGION DURING THE LATTER HALF OF THE WEEK. IF THIS OCCURS...THE HOTTEST TEMPERATURES THUS FAR THIS SUMMER WILL BE LIKELY WITH HEAT INDEX VALUES WELL INTO THE 90S TO NEAR 100 IN SOME AREAS. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. 15
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PITTSBURGH PA
1215 PM EDT MON JUL 18 2011
PAZ007>009-181715-
FOREST PA-MERCER PA-VENANGO PA-
1215 PM EDT MON JUL 18 2011
...STRONG THUNDERSTORMS WILL AFFECT NORTHERN FOREST...NORTHERN MERCER
AND NORTHERN VENANGO COUNTIES...
AT 1208 PM EDT...STRONG THUNDERSTORMS WERE ALONG A LINE FROM 18 MILES
NORTH OF PLEASANTVILLE TO 7 MILES WEST OF CONNEAUT LAKE...MOVING
SOUTHEAST AT 25 MPH.
WIND GUSTS TO 50 MPH AND HAIL UP TO DIME SIZE ARE POSSIBLE WITH THESE
STORMS. THERE CAN ALSO BE LOCALLY HEAVY RAIN AND A SHORT INTERVAL OF
FREQUENT LIGHTNING.
SOME LOCATIONS THAT WILL BE IMPACTED INCLUDE...
GREENVILLE... MAURICE K GODDARD STATE PARK...
PLEASANTVILLE... WEST HICKORY...
OIL CREEK STATE PARK... LYNCH...
COOPERSTOWN... BALLTOWN...
WHEN THUNDERSTORMS THREATEN...GO INDOORS IF YOU CAN.
DO NOT DRIVE YOUR VEHICLE INTO AREAS WHERE THE WATER COVERS THE
ROADWAY. THE WATER DEPTH MAY BE TOO GREAT TO ALLOW YOUR CAR TO CROSS
SAFELY. MOVE TO HIGHER GROUND. CAMPERS...WATCH STREAM LEVELS AND BE
READY TO MOVE TO HIGHER GROUND.
PLEASE REPORT SIGNIFICANT WEATHER TO THE NATIONAL WEATHER SERVICE BY
CALLING TOLL FREE...877-633-6772...WHEN YOU CAN DO SO SAFELY.
LAT...LON 4162 7895 4159 7897 4140 8000 4139 8051
4142 8053 4149 8052 4149 8001 4163 7983The Pittsburgh radar (KPBZ), 94 km away, was scanning. The volume nearest the first event began at 17:05 UTC.
6 thunderstorm wind, 2 flood, 1 flash flood. Local standard time, as filed.
A trained spotter reported a large tree down on power lines.
A trained spotter reports trees and a utility pole down.
The media reports trees and power lines down in Renfrew.
Washington Blvd/Route 8 at the Negley Run intersection was closed due to rapidly rising water. Numerous cars were stranded or stalled with two people needing to be rescued from their vehicles.
Emergency management reports trees down outside of Rochester.
The Pittsburgh Tribune Review reports that a half dozen motorists were stuck when their vehicles stalled in high water on Route 51 between Coal Valley Rd in Jefferson Hills and the Southland Four Seasons shopping center in Pleasant Hills.
Beaver Times newspaper reports of flooding on Route 65 near Fourth Street, just north of Ambridge. Water was waist deep and stalled vehicles.
Duquesne Light reported downed trees and wires in Baldwin, Findley, Leet, Liberty, Port Vue, and Moon.
Pennsylvania Department of Transportation reports a couple of trees down on Ginger Hill Road.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Pennsylvania in 2011Every state in 2011This day in weather historyWarnings in Pennsylvania, July 2011
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: 334588, 334590, 334591, 334622, 334593, 334625, 334626, 334600, 334596.