Low visibility episodes (visibility < 1000 m) were studied by applying the anomaly-based weather analysis method.A regional episode of low visibility associated with a coastal fog that occurred from 27 to 28 January 2016 over NingboZhoushan Port,Zhejiang Province,East China,was first examined.Some basic features from the anomalous weather analysis for this case were identified:(1) the process of low visibility mainly caused by coastal fog was a direct response to anomalous temperature inversion in the lower troposphere,with a warm center around the 925 hPa level,which was formed by a positive geopotential height (GPH) anomaly in the upper troposphere and a negative GPH anomaly near the surface;(2) the positive humidity anomaly was conducive to the formation of coastal fog and rain;(3) regional coastal fog formed at the moment when the southwesterly wind anomalies transferred to northeasterly wind anomalies.Other cases confirmed that the low visibility associated with coastal fog depends upon low-level inversion,a positive humidity anomaly,and a change of wind anomalies from southwesterly to northeasterly,rain and stratus cloud amount.The correlation coefficients of six-hourly inversion,850-925-hPa-averaged temperature,GPH and humidity anomalies against visibility are-0.31,0.40 and-0.48,respectively,reaching the 99% confidence level in the first half-years of 2015 and 2016.By applying the anomaly-based weather analysis method to medium-range model output products,such as ensemble prediction systems,the anomalous temperature-pressure pattern and humidity-wind pattern can be used to predict the process of low visibility associated with coastal fog at several days in advance.