Senior Meteorologist Abdur Rahman Khan told bdnews24.com a trough of low lies in northern Bay causing deep convections.
Squally weather may affect the seaports, the North Bay and adjoining coastal areas.
All fishing boats and trawlers at the North Bay have been asked to remain close to shore until further notice, added Khan.
According to the forecast for Friday, light to moderate rain and thunder showers with gusty winds is likely to occur at most places across Bangladesh.
It said some places may experience moderately heavy to very heavy falls.