Uttar Pradesh and Bihar witnessed very dense fog in the wee hours today. The MeT Department said the foggy conditions were observed at isolated places over Sub' Himalayan West Bengal and moderate fog at over Punjab, Haryana, Chandigarh, Delhi and in Assam, Meghalaya and Tripura. <br/><br/>It said, the western disturbance now lies as a low-pressure area over West Rajasthan adjoining Pakistan. It is likely to cause scattered to widespread rainfall over northern plains and rain or snow over the western Himalayan region during the next 48 hours. Isolated hailstorms are also likely over lower parts of Uttarakhand, Haryana and West Uttar Pradesh tomorrow.