EMB-145 Captain reported a fumes event accompanied with a 'Lav Smoke' EICAS message during initial climb. Upon completing the QRH procedures priority handling was requested to departure airport where a safe overweight landing was executed.

Narrative

After takeoff from ZZZ Runway XXC around 600 ft. AGL received LAV SMOKE on EICAS. Smelled odor but couldn't pinpoint the smell. Flight attendant called on Emergency call button and said he saw smoke and the alarm was going off. Continued runway heading and informed departure we [were requesting priority handling] and would be returning to ZZZ. Told the FO (First Officer) to run the QRH for LAV smoke. I continued to fly; talk to ATC and the flight attendant. Called flight attendant for an update after leaving off at 4000 ft. and he said the smoke was gone but the smell was still present. I decided since the possibility of a fire or device possibly catching on fire we needed to land ASAP. Once First Officer was done running the QRH I told him to look at overweight landing and get flap 45 numbers for 46;000. Sent an ACARS to Dispatch letting them know and told the passengers via announcement over the PA we were returning to CLT. Landed with less then 300 FPM decent exited runway and asked the flight attendant if smoke was back and if passengers were okay. Once I got the all clear I cancelled [priority handling] went to the gate and deplaned without incident. CFR checked the plane and bags.