A weak shortwave passing over an upper ridge provided enough lift for the development of isolated to scattered thunderstorms across the high terrain east of Pittsburgh. However, with little shear to support tilted updrafts, some strong to severe wind gusts were realized at the surface as the storms collapsed on themselves.
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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 PBZ wrote it up.
A weak shortwave passing over an upper ridge provided enough lift for the development of isolated to scattered thunderstorms across the high terrain east of Pittsburgh. However, with little shear to support tilted updrafts, some strong to severe wind gusts were realized at the surface as the storms collapsed on themselves.
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 Sep 4, 1:43 PM EST, 2 hours 22 minutes earlier.
AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 243 PM EDT FRI SEP 4 2015 .SYNOPSIS... WARM AND HUMID CONDITIONS WILL CONTINUE THROUGH THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... SHORTWAVE/WEAKNESS IN THE UPPER RIDGE WILL MAINTAIN THE CHANCE FOR SHOWERS AND THUNDERSTORMS THROUGH THE EVENING. IN ADDITION...RESIDUAL OUTFLOW BOUNDARIES FROM THIS MORNINGS COMPLEX WILL ALSO BE A CONTRIBUTING FACTOR...AND A FEW STORMS HAVE ALREADY DEVELOPED IN THE HIGHER TERRAIN. WITH NO SHEAR/UPPER LEVEL FLOW...MOST OF THESE STORMS WILL BE RATHER SHORT LIVED. THUS...SLIGHT TO LOW CHANCE POPS WERE MAINTAINED THROUGH THE PERIOD WITH MOST OF THE CONVECTION EXPECTED TO DISSIPATE WITH THE LOSS OF HEATING AT NIGHTFALL. WHILE TEMPERATURES WILL BE CONTINGENT ON CLOUD COVER AND COVERAGE OF STORMS THIS AFTERNOON...GENERALLY STAYED WITH A PERSISTENCE FORECAST WITH TEMPERATURES REMAINING 5 TO 10 DEGREES ABOVE SEASONAL AVERAGES. && .SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/... H500 RIDGE WILL REESTABLISH ITSELF OVER THE WEEKEND AND CONTINUE TO KEEP MOST WEATHER SYSTEMS AT BAY. WEAK FLOW OUT OF THE EAST AND SOUTHEAST...AROUND A SURFACE HIGH TO OUR EAST...WILL BRING A SLIGHTLY DRIER AND MORE STABLE AIRMASS ON SATURDAY. WITH PWATS FALLING AND H500 TEMPERATURES RISING...EXPECTING LESS DIURNAL CONVECTIVE COVERAGE. LIMITING POPS TO SLIGHT CHANCE...WITH AREAS NORTH AND EAST OF PIT STAYING DRY. RIDGE REACHES ITS BEST STRENGTH ON SUNDAY WITH H500 HEIGHTS AROUND 590DM. THINK CAPPING WILL BE STRONG ENOUGH TO SUPPRESS CONVECTION AND WILL KEEP THE DRY FORECAST GOING. IF POPS NEED TO BE ADDED EVENTUALLY...IT WOULD BE ALONG THE RIDGES. THE RIDGE STARTS TO WEAKEN ON MONDAY AS A LARGE UPPER LOW ACROSS CANADA MOVES EASTWARD...CAUSING HEIGHTS DOWNSTREAM TO BEGIN TO FALL. STILL...THE LACK OF MOISTURE...CONTINUED CAPPING...AND PERSISTENT SPRAWLING SURFACE HIGH WILL KEEP POPS BELOW 15. ANY SIGNIFICANT PRECIPITATION CHANCE WILL WAIT UNTIL MIDWEEK. TEMPERATURES WERE BASED ON A BLEND OF 12Z BIAS-CORRECTED MOSGUIDE AND PREVIOUS NUMBERS...WITH CONTINUED VALUES OF AROUND 10 DEGREES ABOVE NORMAL. CL && .LONG TERM /TUESDAY THROUGH FRIDAY/... THE STRONG MID/UPPER RIDGE IS PROGGED TO REMAIN THROUGH EARLY NEXT WEEK...WITH CONTINUED WARM AND MUGGY CONDITIONS. RELIEF FROM THE QUITE WARM CONDITIONS MAY COME WITH COLD FRONT LATER WEDNESDAY INTO THURSDAY...AS WELL AS AN INCREASING CHANCE FOR THUNDERSTORMS. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... EXPECT PREVAILING VFR CONDITIONS FOR MUCH OF THE AFTERNOON AND EVENING WITH A SMALL CHANCE OF RESTRICTIONS IN ANY SHOWER OR THUNDERSTORM THAT PASSES DIRECTLY OVER A TAF SITE. WITH LIMITED CONFIDENCE IN ANY ONE SPECIFIC PORT BEING IMPACTED...OPTED TO LEAVE TS MENTION OUT FOR NOW. EXPECT ANOTHER ROUND OF FOG OVERNIGHT WITH PLENTY OF LOW LEVEL MOISTURE AND LITTLE MIXING. OUTLOOK...FRIDAY THROUGH TUESDAY... GENERAL VFR WITH BRIEF RESTRICTIONS IN EARLY MORNING FOG IS ANTICIPATED EACH DAY. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. &&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE PITTSBURGH PA 423 AM EDT FRI SEP 4 2015 MDZ001-OHZ039>041-048>050-057>059-068-069-PAZ007>009-013>016-020>023- 029-031-073>076-WVZ001>004-012-021>023-041-050830- 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- 423 AM EDT FRI SEP 4 2015 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. NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY. 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 PITTSBURGH PA
343 PM EDT FRI SEP 4 2015
PAZ023-074-042015-
INDIANA-WESTMORELAND RIDGES-
343 PM EDT FRI SEP 4 2015
...A STRONG THUNDERSTORM WILL AFFECT SOUTH CENTRAL INDIANA COUNTY...
AT 343 PM EDT...A STRONG THUNDERSTORM WAS NEAR BLACK LICK...OR NEAR
HOMER CITY...MOVING WEST AT 10 MPH.
WIND GUSTS UP TO 50 MPH AND HALF INCH HAIL ARE POSSIBLE WITH THIS
STORM.
LOCATIONS IMPACTED INCLUDE...
HOMER CITY...BLACK LICK...SEWARD...BOLIVAR...ARMAGH...LUCERNE MINES
AND BRUSH VLY.
TORRENTIAL RAINFALL IS ALSO OCCURRING WITH THIS STORM...AND MAY CAUSE
LOCALIZED FLOODING. DO NOT DRIVE YOUR VEHICLE THROUGH FLOODED
ROADWAYS.
FREQUENT CLOUD TO GROUND LIGHTNING IS OCCURRING WITH THIS STORM.
LIGHTNING CAN STRIKE 15 MILES AWAY FROM A THUNDERSTORM. SEEK A SAFE
SHELTER INSIDE A BUILDING OR VEHICLE.
LAT...LON 4041 7902 4036 7923 4038 7923 4040 7921
4043 7921 4043 7924 4062 7927 4053 7898
TIME...MOT...LOC 1943Z 095DEG 8KT 4047 7908
15The Pittsburgh radar (KPBZ), 58 km away, was scanning. The volume nearest the first event began at 21:05 UTC.
4 thunderstorm wind. Local standard time, as filed.
Local 911 center reported a large tree down through a house and on a car. Local news station reported a second tree down on property.
Local 911 reported trees and wires down.
Local 911 reported trees down.
Local 911 reported trees down in Mill Creek Township.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Pennsylvania in 2015Every state in 2015This day in weather historyWarnings in Pennsylvania, September 2015
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: 599351, 599345, 599346, 599347.