A potent upper-air disturbance moving southeast from the Great Lakes triggered numerous thunderstorms over northwest Pennsylvania between 3 and 4 pm local time. These storms become severe and eventually organized into large squall line that surged southeast across central and southeastern Pennsylvania during the late afternoon and evening hours. The well-defined, bowing line producing widespread wind damage and localized flash flooding.

Thunderstorm Wind in CLEARFIELD, PENNSYLVANIA
From 27-MAY-12 16:07:00 to 27-MAY-12 16:07:00 (EST-5)
Location: MAHAFFEY JCT
Magnitude: 61.00 EG
Property damage: 10.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated between 60 and 80 mph knocked down trees around Mahaffey. The damaging winds also toppled a rather large (1.5 ton) grave site marker (obelisk) in La Jose.

Thunderstorm Wind in ELK, PENNSYLVANIA
From 27-MAY-12 15:30:00 to 27-MAY-12 15:30:00 (EST-5)
Location: RIDGWAY
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down trees in Ridgway.

Thunderstorm Wind in CLEARFIELD, PENNSYLVANIA
From 27-MAY-12 15:57:00 to 27-MAY-12 15:57:00 (EST-5)
Location: GRAY
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down trees around Shawville.

Thunderstorm Wind in CAMBRIA, PENNSYLVANIA
From 27-MAY-12 16:34:00 to 27-MAY-12 16:34:00 (EST-5)
Location: NICKTOWN
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down trees in Barr Township near Nicktown.

Thunderstorm Wind in CAMBRIA, PENNSYLVANIA
From 27-MAY-12 17:00:00 to 27-MAY-12 17:00:00 (EST-5)
Location: JOHNSTOWN
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down trees and utility wires in Johnstown.

Thunderstorm Wind in BLAIR, PENNSYLVANIA
From 27-MAY-12 17:00:00 to 27-MAY-12 17:00:00 (EST-5)
Location: HOLIDAYSBURG
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down trees and utility wires in Hollidaysburg.

Thunderstorm Wind in CENTRE, PENNSYLVANIA
From 27-MAY-12 17:19:00 to 27-MAY-12 17:19:00 (EST-5)
Location: INGLEBY
Magnitude: 70.00 EG
Property damage: 15.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

A burst of severe, straight-line winds uprooted or damaged about 50 large trees which subsequently caused damage to about 5 structures in and around the Ingleby area. The exact time a tree fell at the Hemlock Knob home under construction was noted on the camera system.  There were 2 noticeable areas of damage; from Penns Creek to Scenic Drive in Ingleby; and another along the side of Sawmill Knob Mountain adjacent to the state forest lands. At the Scenic Drive location, about 5 to 10 full and partial trees were damaged. They were primarily lying in a W-E or SW-NE direction from estimated wind gusts of 75 mph.  One the trees caused major damage to a summer home while the other homes had mostly minor damage.  At Hemlock Knob there were about 40 large trees uprooted including at least 30 of them in a swath of about 100 yards by 200 yards along the hillside.  The trees were mostly lying in SW-NE direction from estimated wind gusts to 85 to 90 mph.

Thunderstorm Wind in BLAIR, PENNSYLVANIA
From 27-MAY-12 17:00:00 to 27-MAY-12 17:00:00 (EST-5)
Location: MILL RUN
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down trees and wires in Altoona.

Thunderstorm Wind in HUNTINGDON, PENNSYLVANIA
From 27-MAY-12 17:00:00 to 27-MAY-12 17:00:00 (EST-5)
Location: HUNTINGDON
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down trees in Huntingdon.

Thunderstorm Wind in BLAIR, PENNSYLVANIA
From 27-MAY-12 17:04:00 to 27-MAY-12 17:04:00 (EST-5)
Location: WILLIAMSBURG
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down trees and utility wires in Williamsburg.

Thunderstorm Wind in SOMERSET, PENNSYLVANIA
From 27-MAY-12 17:09:00 to 27-MAY-12 17:09:00 (EST-5)
Location: JEROME
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down trees and wires in Conemaugh Township near Jerome.

Flash Flood in COLUMBIA, PENNSYLVANIA
From 27-MAY-12 20:00:00 to 28-MAY-12 00:00:00 (EST-5)
Location: CATAWISSA
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Emergency Manager

Heavy thunderstorm rains caused streams and creeks to overflow their banks in Catawissa and Franklin Townships, taking large objects including cars downstream in the flood waters.

Thunderstorm Wind in HUNTINGDON, PENNSYLVANIA
From 27-MAY-12 17:15:00 to 27-MAY-12 17:15:00 (EST-5)
Location: MILL CREEK
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down trees in Mill Creek.

Thunderstorm Wind in MIFFLIN, PENNSYLVANIA
From 27-MAY-12 17:18:00 to 27-MAY-12 17:18:00 (EST-5)
Location: LEWISTOWN
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph produced widespread damage across much of the county.

Thunderstorm Wind in SOMERSET, PENNSYLVANIA
From 27-MAY-12 17:21:00 to 27-MAY-12 17:21:00 (EST-5)
Location: STOYSTOWN
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down trees and utility wires in Stoystown.

Thunderstorm Wind in HUNTINGDON, PENNSYLVANIA
From 27-MAY-12 17:20:00 to 27-MAY-12 17:20:00 (EST-5)
Location: MT UNION
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down trees in Mt. Union.

Flash Flood in CAMBRIA, PENNSYLVANIA
From 27-MAY-12 21:30:00 to 28-MAY-12 12:15:00 (EST-5)
Location: WESTWOOD
Flood cause: Heavy Rain
Property damage: 0.00K
Crop damage: 0.00K
Reported by: State Official

Intense heavy rainfall resulted in stream flooding along at least eight roadways in the Johnstown area. Two roads were closed and 19 basements were flooded.  One bridge was reported to be sagging after the flooding and was closed for repairs.

Thunderstorm Wind in JUNIATA, PENNSYLVANIA
From 27-MAY-12 17:30:00 to 27-MAY-12 17:30:00 (EST-5)
Location: PORT ROYAL
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down numerous trees across the county.

Hail in CAMBRIA, PENNSYLVANIA
From 27-MAY-12 16:53:00 to 27-MAY-12 16:53:00 (EST-5)
Location: EBENSBURG
Magnitude: 0.75 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Penny size hail was reported in Ebensburg.

Hail in BEDFORD, PENNSYLVANIA
From 27-MAY-12 17:39:00 to 27-MAY-12 17:39:00 (EST-5)
Location: SAXTON
Magnitude: 0.88 
Property damage: 0.00K
Crop damage: 0.00K
Reported by: Trained Spotter

Nickel size hail was reported in Saxton.

Thunderstorm Wind in PERRY, PENNSYLVANIA
From 27-MAY-12 17:41:00 to 27-MAY-12 17:41:00 (EST-5)
Location: ESHEOL
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down trees in Ickesburg.

Thunderstorm Wind in PERRY, PENNSYLVANIA
From 27-MAY-12 17:48:00 to 27-MAY-12 17:48:00 (EST-5)
Location: LANDISBURG
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down trees in Landisburg.

Thunderstorm Wind in CUMBERLAND, PENNSYLVANIA
From 27-MAY-12 18:06:00 to 27-MAY-12 18:06:00 (EST-5)
Location: CARLISLE
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down trees in and around Carlisle.

Thunderstorm Wind in CUMBERLAND, PENNSYLVANIA
From 27-MAY-12 18:13:00 to 27-MAY-12 18:13:00 (EST-5)
Location: MECHANICSBURG
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down trees in Hampden Township near Mechanicsburg.

Thunderstorm Wind in CUMBERLAND, PENNSYLVANIA
From 27-MAY-12 18:25:00 to 27-MAY-12 18:25:00 (EST-5)
Location: NEW CUMBERLAND
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down trees and utility wires in New Cumberland.

Thunderstorm Wind in DAUPHIN, PENNSYLVANIA
From 27-MAY-12 18:25:00 to 27-MAY-12 18:25:00 (EST-5)
Location: HARRISBURG
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down trees in Harrisburg.

Thunderstorm Wind in ADAMS, PENNSYLVANIA
From 27-MAY-12 18:30:00 to 27-MAY-12 18:30:00 (EST-5)
Location: BENDERSVILLE
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down trees in Bendersville.

Thunderstorm Wind in FRANKLIN, PENNSYLVANIA
From 27-MAY-12 18:20:00 to 27-MAY-12 18:20:00 (EST-5)
Location: CHAMBERSBURG
Magnitude: 76.00 MG
Crop damage: 0.00K
Reported by: Trained Spotter

Spotter measured a peak thunderstorm wind gust of 87 mph.

Thunderstorm Wind in YORK, PENNSYLVANIA
From 27-MAY-12 18:45:00 to 27-MAY-12 18:45:00 (EST-5)
Location: DOVER
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down trees in Dover.

Thunderstorm Wind in MONTOUR, PENNSYLVANIA
From 27-MAY-12 19:11:00 to 27-MAY-12 19:11:00 (EST-5)
Location: DANVILLE
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down trees and utility wires in Danville.

Thunderstorm Wind in FRANKLIN, PENNSYLVANIA
From 27-MAY-12 18:20:00 to 27-MAY-12 18:20:00 (EST-5)
Location: CHAMBERSBURG
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph damaged a roof in Hamilton Township near Chambersburg.

Thunderstorm Wind in BEDFORD, PENNSYLVANIA
From 27-MAY-12 17:27:00 to 27-MAY-12 17:27:00 (EST-5)
Location: SAXTON
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: State Official

Thunderstorm winds estimated near 60 mph knocked down a few trees in Saxton. One downed treed blocked Cove Mountain Road. A gustnado was photographed near Saxton but produced little damage. A gustnado is a specific type of short-lived, low-level rotating cloud that can form on the leading edge of strong thunderstorm outflow.