A steep pressure gradient lies over the North Bay and adjoining areas and a deep convection is taking place under its influence, said Meteorologist Muhammad Arif Hossain.
"Squally weather may affect the maritime ports, North Bay and adjoining coastal areas of Bangladesh," he said.
All fishing boats and trawlers over north Bay have been advised to come close to the coast and proceed with caution until further notice.
Monsoon is active over southern Bangladesh and strong over North Bay, according to Friday's weather bulletin.
The Met Office has forecast light to moderate rain and thundershowers in most parts of Khulna, Barishal, Chattogram and Dhaka divisions in the next 24 hours.
The southern part of the country is likely to experience moderately heavy to heavy rainfall during that period.