Chennai, Dec 16 (Reporter) A Fresh Low Pressure Area has formed over the Bay of Bengal, the third in succession, and it is expected to become more marked and move towards the Tamil Nadu coast, promising heavy rains for two days. Met office on Monday said under the influence of an upper air circulation over Southeast Bay of Bengal, a Low Pressure Area has formed over central parts of South Bay of Bengal at 0830 hrs today. The associated upper air cyclonic circulation extends up to 3.1 km above mean sea level. It is likely to become more marked and move west-northwestwards towards Tamil Nadu coast during the next 2 days. Under its influence, light to moderate rainfall is likely at many places over North Coastal Tamil Nadu, Puducherrry and Karaikal areas on December 17 and 18 and at a few places over North Tamil Nadu on December 19. Light to moderate rain is also at a few places over Tamil Nadu, at many places over North Coastal Tamil Nadu and at one or two places over rest of the State, Puducherry and Karaikal area with thunderstorm and lighting at one or two places. Heavy to very heavy rain is likely to occur at isolated places over Chengalpattu, Cuddalore, Villupuram, Mayiladuthurai districts of Tamil Nadu and Puducherry tomorrow, where an Orange Alert was issued. Heavy rain is also likely to occur at isolated places over Chennai, Kancheepuram, Tiruvallur, Tiruvarur, Nagapattinam districts of Tamil Nadu and Karaikal area (Yellow alert issued). On December 18, hHeavy to very heavy rain is likely to occur at isolated places over Chennai, Chengalpattu, Tiruvallur, Kancheepuram, Cuddalore and Villupuram districts of Tamil Nadu and Puducherry (Orange alert issued). Heavy rain is also likely to occur at isolated places over Ranipet, Tiruvannamalai, Kallakurichi, Vellore, Ariyalur, Mayiladuthurai districts of Tamil Nadu and Karaikal area (Yellow alert issued). On December 19, heavy rain is likely to occur at isolated places over Chennai, Chengalpattu, Tiruvallur and Kancheepuram districts, where an Yellow alert was issued. Squally weather with wind speed ranging 35 kmph to 45 kmph and gusting up to 55 kmph is likely to prevail along and off South Tamil Nadu coast, adjoining Comorin area and Gulf of Mannar. Tomorrow, squally weather with wind speed ranging 35 kmph to 45 kmph and gusting up to 55 kmph is likely to prevail along and off Tamil Nadu coast, adjoining Comorin area and Gulf of Mannar. On December 18 and 19, squally weather with wind speed ranging 35 kmph to 45 kmph and gusting up to 55 kmph is likely to prevail along and off Tamil Nadu coast, adjoining Gulf of Mannar and South Andhra Pradesh coast and Comorin area,. Fishermen are advised not to venture into the above sea areas during thse period...////...