New Delhi, Dec 27 : A thick blanket of fog covered parts of Delhi-NCR on Wednesday morning, leading to a considerable drop in visibility. Traffic was slow and commuters had difficulty reaching their destinations. The India Meteorological Department (IMD) had said that dense to very dense fog is likely to continue over Northwest India and parts of Central India during the next three-four days. 'Dense fog conditions are very likely to continue in early hours/morning hours in isolated pockets over Odisha, Uttarakhand on Wednesday and Thursday over Haryana, Chandigarh, Delhi and Uttar Pradesh on Saturday and Sunday and over Assam, Meghalaya, Nagaland, Manipur, Mizoram and Tripura during Wednesday-Sunday,' it said on Tuesday. The IMD also predicted that a fresh Western Disturbance is likely to affect Northwest India from Saturday. 'Under its influence and its interaction with lower level easterly winds, light isolated rainfall is likely over Northwest and adjoining Central India during December 30-January 2,' the IMD said. /IANS