Unexpected isolated strong storms into BGE service area June 18th Discussion: A thunderstorm formed north-northeast of Martinsburg, WV mid-afternoon Monday June 18th and moved east-southeast and intensifying reaching the BGE Service Area in-between 4 and 5 PM. The storm is characterized as “severe” by Climate Impact Company due to the likelihood of wind gusts exceeding 50 MPH to cause storm reports in Carroll, Howard and Baltimore Counties (Table 1). Location Character Time Sykesville, Carroll County Multiple trees/wires down. 4:20 PM Gaither, Howard County Downed trees 4:23 PM Towson, Baltimore County Multiple reports of trees down 4:28 PM Friendship, Howard County Downed trees 4:28 PM Pikesville, Baltimore County Multiple trees down, blocked roads 4:44 PM Pikesville, Baltimore County Multiple trees down 4:47 PM Table 1: Storm Prediction Center report of damage caused by high wind related to a severe thunderstorm in the BGE Service Area yesterday. Radar indicates the rainfall that occurred with these storm was minor, generally 0.25 to 0.50 in. mostly on the lower end of that range. Hot temperatures and high humidity caused convective available potential energy (CAPE) values to easily eclipse 2000 j/kg which supports strong to severe thunderstorms if a trigger to ignite activity is present. Fig 1: The high-resolution rapid refresh (HRRR) model depiction of thunderstorm activity in the BGE Service Area between 4 and 5 PM Monday June 18 is indicated. Fig. 2: Convective available potential energy forecast across the BGE Service Area ahead of the approaching thunderstorms indicated buoyant >2000 J/KG range certainly supporting strong-to-severe thunderstorms. Summary: A large area of severe thunderstorms producing many wind damage reports occurred across the Northeast U.S. on Monday. The event affecting the BGE Service Area between 4 and 5 PM Monday afternoon was not part of that complex but rather an isolated thunderstorm which became severe moving into an area of high instability across the BGE Service Area. The storm was likely initiated by the elevated terrain in south-central Pennsylvania rather than any synoptic meteorological diagnostic. Once the storm developed and moving east-southeast the drift into the unstable atmosphere across the BGE Service Area enabled intensification. Although not officially measured the damage reported by this isolated storm indicates wind gusts exceeding 50 mph qualifying the storm as severe. Fig. 3: Storm Prediction Center reports of damage caused by severe thunderstorms on Monday June 18th. The isolated severe thunderstorm affecting the BGE Service Area was not part of a larger severe weather outbreak to the north.