New Delhi : The southwest monsoon on Sunday further advanced into central Arabian Sea, thus covering further parts of the country, including the entire northeastern region. The monsoon, which hit Kerala two days ago, has advanced into most parts of sub-Himalayan West Bengal and Sikkim, some more parts of Maharashtra, the entire Karnataka and Tamil Nadu, some more parts of Telangana, and Andhra Pradesh, central Bay of Bengal and northeast Bay of Bengal, the India Meteorological Department (IMD) said. Due to strengthening of southwesterly winds and a cyclonic circulation over sub-Himalayan West Bengal and neighbourhood in lower tropospheric level, the IMD predicted fairly widespread to widespread rainfall activitywas very likely over northeastern states and adjoining east India during next 4-5 days. Isolated heavy rainfall is very likely over Arunachal Pradesh on Sunday and Tuesday; over Assam and Meghalaya and sub-Himalayan West Bengal and Sikkim on Tuesday and Wednesday; over Nagaland, Manipur, Mizoram and Tripura on Sunday and Monday; over Odisha on Tuesday and Wednesday; and over Gangetic West Bengal on Thursday. Isolated heavy to very heavy rainfall is also very likely over Assam and Meghalaya and sub-Himalayan West Bengal and Sikkim on Sunday and over Odisha on Thursday, the IMD said. Under the influence of the offshore trough at mean sea level from north Maharashtra coast to north Kerala coast and a cyclonic circulation over Konkan and Goa in lower tropospheric levels, scattered to widespread rainfall accompanied with thunderstorm, lightning and gusty winds is very likely over parts of south peninsular India and the west coast with isolated heavy rainfall on Sunday and reduction in intensity thereafter.