The National Weather Service in Pittsburgh has confirmed that two tornadoes have touched down in Southwest Pennsylvania during the early morning hours on Wednesday.
The first was an EF-1 tornado that touched down in Allegheny County 3 miles northwest of Tarentum at around 1:10am and brought winds up to 100mph in a path that extended 4.1 miles in length and reached 150 yards wide.
Modest tree damage was first noted a bit south of the intersection of Days Run Road and Gillespie road. The tornado rapidly intensified near Days Run Road and Holsing lane,
Where a vast number of softwood and hardwood trees were snapped, blocking Days Run Road, with some falling onto homes. Additionally in this location, windows on a home were blown in by the tremendous wind.
The wind slowly weakened as the storm continued southeastward, with a path of snapped limbs and occasional trunks continuing to along Bakerstown road near the Broadview Section before continuing across Route 28. Modest building/carport damage was reported in Tarentum along Sixth Ave coincident with the passage of the weakening circulation. The modest damage continued sporadically across the river, where tree limbs and a power pole were snapped in a neighborhood behind Riverview Plaza. The last noted tree damage was along Leechburg Road north of Tarentum road, at which point the circulation appears to have weakened below damaging threshold.
Damage reported farther south in New Kensington appears to be the result of strong straight-line wind associated with a surge in the cold outflow air emerging from the line of storms. While non-tornadic, straight-line wind speed in such storms often can be
stronger than an embedded tornado, causing similar intense damage.
The second tornado was an EF-0 tornado that touched down at 1:17am near Braeburn, Westmoreland County. This tornado had maximum winds of 70mph and a path lenth of a quarter mile with a maximum width of 75 yards.
This brief tornado was documented along Riverview Street in Lower Burrell. A narrow path consisting mainly of snapped and uprooted trees and limbs was encountered. Additionally, modest damage to shingles and fences was noted. Supporting the presence
of a strong circulation, splatter of mud, pine needles and debris was discovered on the east-facing side of affected homes, and downwind lawn furniture and trampolines were lofted and deposited westward from their initial locations.
Wind was fairly focused, with damage consistent with 70 mph wind gusts. This brief tornado was associated with a second mesovortex/updraft distinct from the Tarentum/New Kensington tornado.