A slow moving low pressure system, and it's associated cold front crossed through the region late in the day on the 26th. Scattered severe thunderstorms, most of which produced wind damage, developed along the frontal boundary in an area of instability and high shear.
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 slow moving low pressure system, and it's associated cold front crossed through the region late in the day on the 26th. Scattered severe thunderstorms, most of which produced wind damage, developed along the frontal boundary in an area of instability and high shear. A microburst occurred in Monongalia county in West Virginia with an estimated wind speed of 70-80 mph.
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 May 25, 9:51 PM EST, 2 hours 39 minutes earlier.
AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE PITTSBURGH PA 1051 PM EDT WED MAY 25 2011 .SYNOPSIS... WARM AND HUMID CONDITIONS ALONG WITH THUNDERSTORM CHANCES WILL CONTINUE FOR THE REST OF THE WEEK AS A SERIES OF DISTURBANCES CROSS THE REGION. && .NEAR TERM /THROUGH THURSDAY/... LINE OF STRONG TO SEVERE STORMS IS DISSIPATING AS IT CONTINUES TO MOVE EASTWARD ACROSS THE NORTHERN HALF OF THE FORECAST AREA. MORE ACTIVITY IS DEVELOPING TO THE WEST, BUT THIS IS HEADING NORTH OF THE CWA. WILL KEEP HIGHEST POPS TO THE NORTH AND CHANCE POPS SOUTH AND WEST. WILL LIKELY NEED ANOTHER UPDATE AS ACTIVITY CONTINUES TO WIND DOWN. THE FORECAST AREA WILL REMAIN IN THE WARM SECTOR THROUGH THURSDAY. THUNDERSTORMS WILL BECOME MORE LIKELY IN EASTERN OHIO BY THURSDAY AFTERNOON AS WARMER TEMPS AND HIGHER HUMIDITY INCREASE INSTABILITY AND AS COLD FRONT SLIDES FURTHER EASTWARD FROM INDIANA. THE FORECAST AREA REMAINS IN A SLIGHT RISK OF SEVERE STORMS FOR TONIGHT THROUGH THURSDAY. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY/... AS THE COLD FRONT DRAWS CLOSER THURSDAY NIGHT INTO FRIDAY SHOWERS AND THUNDERSTORMS WILL BE MORE LIKELY WITH INCREASED COVERAGE OF SHOWERS. THE FORECAST AREA REMAINS IN THE SLIGHT RISK OF SEVERE FOR THURSDAY NIGHT. THE RISK OF SHOWERS WILL GREATLY DIMINISH AS THE COLD FRONT BECOMES MORE DIFFUSE BY LATE FRIDAY AND IS OVERWHELMED BY THE RIDGE OF HIGH PRESSURE OFF THE EAST COAST. TEMPERATURES WILL REMAIN ABOVE NORMAL. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... MEDIUM RANGE MODELS ARE SHOWING AGREEMENT FOR AN EXTENDED DRY PERIOD BEGINNING SATURDAY AND CONTINUING THROUGH TUESDAY. INCREASING MOISTURE WILL BRING A SLIGHT CHANCE OF SHOWERS BY WEDNESDAY. MUCH ABOVE NORMAL TEMPS ARE EXPECTED FOR THE FORECAST PERIOD. && .AVIATION /03Z THURSDAY THROUGH MONDAY/... EXPECT GENERALLY VFR CONDITIONS TO PREVAIL THROUGH THE TAF PERIOD FOR MOST PORTS; HOWEVER, THUNDERSTORMS, RESTRICTIONS, AND GUSTY WIND ARE POSSIBLE MAINLY ACROSS NORTHERN AND WESTERN TERMINALS INTO THE EARLY MORNING HOURS. ANOTHER LINE OF SHOWERS AND THUNDERSTORMS MAY PUSH THROUGH BETWEEN 08Z- 12Z...WITH GUSTY WINDS THE MAIN THREAT. THIS SECOND LINE WILL NEED TO BE ADDRESSED ONCE CONVECTION DEVELOPS AS MUCH OF THE ACTIVITY TO THE WEST IS HEADING NORTHWARD AND IS EXPECTED TO WEAKEN DURING THE EARLY MORNING HOURS. MORE THUNDERSTORMS ARE EXPECTED THURSDAY AND THURSDAY NIGHT AS A SURFACE LOW AND COLD FRONT APPROACH FROM THE WEST. OCCASIONAL MVFR AND ISOLATED IFR RESTRICTIONS CAN BE EXPECTED IN STORMS ALONG WITH THE POTENTIAL FOR HAIL AND GUSTY SURFACE WINDS. NUMEROUS SHOWERS AND AND SCATTERED THUNDERSTORMS WILL CONTINUE FRIDAY AND FRIDAY NIGHT AS THE SURFACE LOW PUSHES ACROSS THE GREAT LAKES AND THE COLD FRONT SLOWLY CROSSES THE UPPER OHIO VALLEY. GENERALLY VFR CONDITIONS ARE EXPECTED THIS WEEKEND AS AN UPPER RIDGE BUILDS OVER THE REGION. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. &&
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE PITTSBURGH PA 419 AM EDT WED MAY 25 2011 OHZ039>041-048>050-057>059-068-069-PAZ007>009-013>016-020>023-029- 031-073-075-WVZ001>004-012-021-022-260830- 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-FAYETTE-HANCOCK-BROOKE-OHIO- MARSHALL-WETZEL-MARION-MONONGALIA- 419 AM EDT WED MAY 25 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR EAST CENTRAL OHIO...NORTHWEST PENNSYLVANIA...SOUTHWEST PENNSYLVANIA...WEST CENTRAL PENNSYLVANIA...NORTHERN WEST VIRGINIA AND NORTHERN PANHANDLE OF WEST VIRGINIA. .DAY ONE...TODAY AND TONIGHT. SLIGHT RISK FOR SEVERE THUNDERSTORMS THIS AFTERNOON AND EVENING. THE MAIN THREAT WILL BE LARGE HAIL AND DAMAGING WINDS. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY. SLIGHT RISK FOR SEVERE THUNDERSTORMS THURSDAY AFTERNOON AND THURSDAY NIGHT. THE MAIN THREAT WILL BE LARGE HAIL AND DAMAGING WINDS. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES. MDZ001-PAZ074-076-WVZ023-041-260830- GARRETT-WESTMORELAND RIDGES-FAYETTE RIDGES-PRESTON-TUCKER- 419 AM EDT WED MAY 25 2011 THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN MARYLAND...SOUTHWEST PENNSYLVANIA AND NORTHERN WEST VIRGINIA. .DAY ONE...TODAY AND TONIGHT. NO HAZARDOUS WEATHER IS NOT EXPECTED AT THIS TIME. .DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY. SLIGHT RISK FOR SEVERE THUNDERSTORMS THURSDAY AFTERNOON AND THURSDAY NIGHT. THE MAIN THREAT WILL BE LARGE HAIL AND DAMAGING WINDS. .SPOTTER INFORMATION STATEMENT... WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PITTSBURGH PA
1035 PM EDT WED MAY 25 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
1010 PM TSTM WND DMG FOXBURG 41.15N 79.68W
05/25/2011 CLARION PA 911 CALL CENTER
LARGE TREES BLOWN DOWN.
&&
EVENT NUMBER PBZ1100766
NWSSPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PITTSBURGH PA
1039 PM EDT WED MAY 25 2011
PAZ009-015-016-022-023-260315-
ARMSTRONG PA-CLARION PA-FOREST PA-INDIANA PA-JEFFERSON PA-
1039 PM EDT WED MAY 25 2011
...THUNDERSTORMS WITH GUSTY WIND WILL AFFECT
JEFFERSON...NORTHEASTERN INDIANA...NORTHERN ARMSTRONG...SOUTHEASTERN
CLARION AND SOUTHEASTERN FOREST COUNTIES...
AT 1034 PM EDT...RADAR INDICATED THUNDERSTORMS ALONG A LINE FROM
MARIENVILLE TO 4 MILES NORTH OF SUMMERVILLE TO 7 MILES WEST OF
MUFF...MOVING EAST AT 40 MPH.
WIND GUSTS OF 40 TO 50 MPH ARE POSSIBLE WITH THESE STORMS.
THESE STORMS WILL BE NEAR MUFF AROUND 1045 PM...DORA AROUND 1050
PM...SMICKSBURG AROUND 1100 PM...PUNXSUTAWNEY AROUND 1105 PM...MARION
CENTER AROUND 1110 PM AND GLEN CAMPBELL AROUND 1115 PM.
PLEASE REPORT SIGNIFICANT WEATHER TO THE NATIONAL WEATHER SERVICE BY
CALLING TOLL FREE...877-633-6772...WHEN YOU CAN DO SO SAFELY.
LAT...LON 4119 7871 4119 7877 4113 7880 4072 7881
4086 7961 4118 7928 4147 7911 4146 7895
4143 7896 4144 7906 4136 7908 4136 7903
4138 7896 4128 7875 4124 7873 4123 7870
15PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PITTSBURGH PA
1050 PM EDT WED MAY 25 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0954 PM TSTM WND DMG CLINTONVILLE 41.20N 79.87W
05/25/2011 VENANGO PA 911 CALL CENTER
LARGE TREE BLOWN DOWN.
&&
EVENT NUMBER PBZ1100767
NWSPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PITTSBURGH PA
1111 PM EDT WED MAY 25 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0935 PM TSTM WND DMG 3 NE NEW CASTLE 41.03N 80.31W
05/25/2011 LAWRENCE PA TRAINED SPOTTER
LARGE TREES BLOWN DOWN ON LAKEWOOD-NESHANNOCK RD...
HICKORY TWP
&&
EVENT NUMBER PBZ1100768
NWSPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PITTSBURGH PA
1114 PM EDT WED MAY 25 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0938 PM TSTM WND DMG 2 WNW HARLANSBURG 41.04N 80.22W
05/25/2011 LAWRENCE PA TRAINED SPOTTER
LARGE TREES BLOWN DOWN ON EAST BROOK-HARLANSBURG RD...
SCOTT TWP
&&
EVENT NUMBER PBZ1100769
NWSPRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PITTSBURGH PA
1118 PM EDT WED MAY 25 2011
..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..
0935 PM TSTM WND DMG 1 E COALTOWN 41.04N 80.33W
05/25/2011 LAWRENCE PA TRAINED SPOTTER
LARGE TREES BLOWN DOWN ON GRACELAND RD... NESHANNOCK
TWP
&&
EVENT NUMBER PBZ1100770
NWSThe Pittsburgh radar (KPBZ), 105 km away, was scanning. The volume nearest the first event began at 05:30 UTC.
22 thunderstorm wind. Local standard time, as filed.
A state official reports large branches and power lines down.
A trained spotter reports that 4 trees are down on Route 68 near the 500 block of Midland.
The public reports large branches broken.
Butler emergency manager reports large trees and a utlity line reported down.
Fire rescue reports several trees down on Monrow St. and David St.
A trained spotter reports a large tree down on Beaver Dam Road.
A trained spotter reports large trees down.
Allegheny emergency management reports large trees down.
Emergency management reports a power line arcing against a house.
The public reports trees down.
Westmoreland emergency management reports a tree down on a house.
Emergency management reports numerous trees down.
Emergency management reports numerous large trees down.
A trained spotter reports that trees and utility lines are down on Fayette Springs Road.
A trained spotter reports a tree down on house and power lines down.
Amateur radio operator reports several trees and power lines down.
Emergency management reports trees down.
Emergency management reports numerous trees down.
Emergency management reports numerous trees and power lines down.
State official reports trees down.
Emergency management reports numerous trees down.
Emergency management reports trees down on Desire 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, May 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: 317644, 317645, 317646, 317647, 317648, 317649, 317650, 317651, 317652, 317653, 317654, 317655, 317656, 317657, 317658, 317659, 317660, 317661, 317662, 317663, 317664, 317665.