India Meteorological Department has a network of S, C, and X band weather radars for weather observations and warning. The radars are a primary tool for issuing nowcast alerts and warnings to the public.The High spatial and temporal resolution of radar aids the forecasters to provide high resolution accurate nowcasts. The alerts and warnings issued are used by the disaster managers to effectively take actions to reduce the impact of severe weather. As the lead time for nowcast is less compared to short range forecast, it is essential that the warning dissemination time is kept at a minimum. This paper discusses an auto-nowcast system which was developed to generate nowcast for 0–2 h based on PySTEPS (an open-source framework for probabilistic precipitation nowcast) and also to generate warnings based on probability of occurrence. Precipitation fields from the past 30 min are used for determining the probability of precipitation for next 2 h in the region of interest. Warnings are triggered based on the probability threshold set in the system. Nowcast warnings are issued automatically by the system for nearly 45 administrative divisions comprising a 6000 sq. km area in 240 s with a computing power of a normal workstation. The performance of the system was validated for cyclone “Mandous” for the region in and around the city of Chennai during the landfall. The Fractional skill scores (1 km) were as high as 0.78 with an average of 0.65 for a 2 h period. Verification has shown that RADCAST has helped to significantly improve the quality of precipitation warning to the public.