New Delhi, Dec. 31 -- A potent combination of atmospheric forces - including the polar vortex, an Arctic blast and a western disturbance - has set the stage for severe cold conditions across northern India, with dense fog and cold day warnings issued through the New Year, the India Meteorological Department (IMD) said on Tuesday. Dense to very dense fog is likely to persist during night and morning hours over Punjab, Haryana, Chandigarh and western Uttar Pradesh on December 31, with eastern Uttar Pradesh remaining affected until January 1. Cold day to severe cold day conditions are forecast over pockets of eastern Uttar Pradesh and Bihar until Wednesday. Under the influence of the western disturbance, heavy rain and snowfall are expected over Jammu and Kashmir and Ladakh until January 1.P3, 17...