New Delhi, Dec. 12 -- After just a two-day breather, Delhi's air quality slid back into the 'very poor' zone on Thursday as stagnant winds once again slowed the dispersion of pollutants, pushing the 24-hour air quality index (AQI) to 305 - up from 259 ('poor') a day earlier, according to the Central Pollution Control Board (CPCB). The India Meteorological Department (IMD) said two back-to-back feeble western disturbances are also set to affect the region, likely raising minimum temperatures in the coming days. Air quality forecasts indicate no immediate relief, with the AQI expected to remain 'very poor'. "Delhi's air quality is likely to be in the 'very poor' category from December 11 till December 13. Outlook for the subsequent six days, from December 14, shows the AQI is likely to stay 'very poor'," said the Centre's Early Warning System (EWS) for Delhi on Thursday. The CPCB classifies air quality as "moderate" when the AQI is between 101 and 200, "poor" between 201 and 300, and "very poor" between 301 and 400. AQI beyond 400 is termed "severe". CPCB data showed deterioration setting in early Thursday as winds slowed, weakening pollutant dispersion. The rolling AQI average stood at 287 at 8 am; 295 at noon; and crossed the 300 threshold before the CPCB's 4pm bulletin was issued. Experts attributed the slide to a sharp fall in wind speed, with fluctuations expected through the week. "Winds up to 20 km/hour blew in the city during the daytime on Wednesday. However, it dipped to around 5 to 8 km/hour on Thursday, and winds briefly rose to 12 km/hour," said Mahesh Palawat, vice-president at Skymet. He added that two feeble western disturbances will influence the region from Saturday....