Chennai. Mar 6 : The Depression over the southwest Bay of Bengal moved southwestwards and weakened into a well marked low pressure area over the same region on Sunday. The IMD in its update said it is likely to move further southweswards towards North Tamil Nadu coast and weaken gradually into a Low Pressure area during the next 24 hrs. The met office said under its influence heavy to very heavy rain is likely to occur at isolated places over Villupuram, Cuddalore, Pudukottai and delta districts of Tamil Nadu and Puducherry and Karaikal area today and tomorrow. On Monday, heavy rain is also likely to occur at isolated places over the districts of Ramanathapuram, Thoothukudi, Sivagangai, Chengalpattu, Kallakurichi, Perambalur, Ariyalur and Tiruchirapalli, while heavy rain is likely to occur at isolated places over Coimbatore, Nilgiris, Dindigul, Theni, Tenkasi and Tiruppur districts on March 8. Thunderstorm with lightning is likely to occur at isolated places over Tamil Nadu, Puducherry and Karaikal area. GV 1253