The paper presents a methodology for short-term assessment of the risk of aircraft separation loss for short-term conflict prevention systems. The paper describes the rules for normalizing risk indicators and aggregating them into a single index with interpretation based on the levels of operational attention (warning/action). The paper also provides an algorithmic protocol for applying the methodology, which includes verification on archived tracks, the formation of reference index distributions, and the adaptation of thresholds to a specific sector (route or terminal). The paper discusses the limitations associated with the quality of observations and the linearity of short-term forecasts. The method is designed to unify STCA settings, reduce false alarms while maintaining the required sensitivity, and provide a reporting mechanism for short-term risks in air traffic control.