In the wake of morning rain, cloud breaks developed from Virginia into south central Pennsylvania during the afternoon.  CAPE values climbed to near 1000 J/kg, despite poor mid-level lapse rates.  Disturbances rotating around the southeastern periphery of a Great Lakes/upper Ohio Valley trough helped to increase low level flow and shear.  This proved sufficient to allow afternoon storms to rotate.
Westmoreland County bore the brunt of the damage, with two short-track EF0 tornadoes confirmed. One in the Hempfield Township/Mount Pleasant area mainly caused tree damage, although damage was done to a barn and outbuildings along Brinker Road.  The second tornado in Unity Township, near Arnold Palmer Regional Airport, mainly caused tree damage as well, along with damage to a barn roof and other minimal home damage. Straight-line wind damage was apparent in other areas in the county.

Tornado in WESTMORELAND, PENNSYLVANIA
From 27-JUN-18 19:20:00 to 27-JUN-18 19:23:00 (EST-5)
Location: WHITNEY
Tornado F-scale: EF0
Property damage: 10.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

An EF-0 tornado touched down just to the southwest of Arnold Palmer Regional Airport.  The most-significant damage in this area was discovered along Henrys Road and Whitfield Road in Unity Township. In this area, light damage to tree limbs was first noted, which escalated considerably along Henrys Road. One property in this vicinity suffered widespread damage to trees, and an open-faced barn lost a large section of
its roof. Although much damage to trees was noted, minimal damage to homes from wind was observed.

Thunderstorm Wind in WESTMORELAND, PENNSYLVANIA
From 27-JUN-18 19:03:00 to 27-JUN-18 19:03:00 (EST-5)
Location: SOUTHWEST
Magnitude: 50.00 EG
Property damage: 5.00K
Crop damage: 0.00K
Reported by: Law Enforcement

County law enforcement reported that a tree fell onto a house along Cannonball Court.

Thunderstorm Wind in WESTMORELAND, PENNSYLVANIA
From 27-JUN-18 19:05:00 to 27-JUN-18 19:05:00 (EST-5)
Location: NORVELT
Magnitude: 50.00 EG
Property damage: 0.50K
Crop damage: 0.00K
Reported by: Law Enforcement

County law enforcement reported multiple trees down near Reservoir Road just west of Norvelt.

Thunderstorm Wind in WESTMORELAND, PENNSYLVANIA
From 27-JUN-18 19:05:00 to 27-JUN-18 19:05:00 (EST-5)
Location: ARMBRUST
Magnitude: 50.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Emergency Manager

The county emergency manager reported that trees and wires were blown down along Route 819 in Mount Pleasant Township.

Thunderstorm Wind in WESTMORELAND, PENNSYLVANIA
From 27-JUN-18 19:20:00 to 27-JUN-18 19:20:00 (EST-5)
Location: BAGGALEY
Magnitude: 50.00 EG
Property damage: 1.00K
Crop damage: 0.00K
Reported by: Emergency Manager

The county emergency manager reported that trees and power lines were down along Gravel Hill Road.

Tornado in WESTMORELAND, PENNSYLVANIA
From 27-JUN-18 19:02:00 to 27-JUN-18 19:10:00 (EST-5)
Location: ARMBRUST
Tornado F-scale: EF0
Property damage: 15.00K
Crop damage: 0.00K
Reported by: NWS Storm Survey

The tornado began in a field between the Pennsylvania Turnpike
and Brinker Road, where it caused damage to trees and a barn along
Brinker Road. A section of the barn's roof was lifted off, as was
the roof of a side building. A heavy dairy condenser unit was
lifted out of this enclosed building after the roof was removed.
Several metal roof panels from this building were lofted and
circulated downwind during the tornado's life.
Damage thereafter was spotty and limited to tree debris, but
the tornado appeared to resume its intensity after the
circulation crossed Armbrust Hecla Road. Residents reported seeing
water being lofted from a lake along Cannonball Court as the
tornado strengthened, with numerous trees being snapped and
uprooted along Cannonball Court/Pheasant Run/Udell Road. A wooden
pool fence in this area also was destroyed.
The tornado weakened again as it moved along Udell Road, with very
limited tree damage apparent along its path. Based on multiple
videos submitted from the Brinkerton Road/Sewickley Creek Road
area showing a ground circulation, an aerial survey conducted by
the Westmoreland County EMA confirmed additional damage.
Damage in this area mainly was in the form of snapped/uprooted trees, and
was consistent with an EF-0 rating.