Flight Crew Air Transport Pilot (ATP)
Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Provided Assistance; Flight Crew Returned To Departure Airport
Weather
After departure ATC provided vectors to facilitate a departure climb providing for aircraft separation and weather avoidance South and West of the field. Subsequently being vectored Northbound a climb clearance was issued. As our aircraft approached 18;000 ft the windscreen was rapidly enveloped in a blanket of St. Elmo's fire; followed by an immediate blinding white flash-over accompanied by an explosive concussion. The First Officer was PF (Pilot Flying) and continued in that capacity. We briefly discussed the nature of the event then requested a lower top end altitude from ATC. During this time we assessed aircraft systems status; completed the Lightning Strike QRH checklist; communicated the nature of the incident to the Cabin Crew and conferred briefly with Maintenance. Uncertain as to the full impact the strike may have had on the aircraft and the specter of a flight into mountainous terrain; FO (First Officer) and I agreed that the safest course of action was to return so that the airworthiness of the aircraft could be determined. [Notified] ATC of our intention of returning to [the departure airport]. The Overweight Landing QRH Checklist was completed; Dispatch notified via ACARS; Landing QRH Checklist completed; and passengers notified as to the nature of the situation and pending return. At this juncture; I assumed PF duties while FO transitioned to PM (Pilot Monitoring) duties. A successful landing was accomplished. After clearing the runway no defects were indicated. After coordinating with Operations taxi to gate was accomplished.
B737 Captain reported a lightning strike at FL180. The crew elected to return to the departure airport.