The invention refers to method, performed by a network optimization function associated with a wireless network (100), of forecasting performance issues associated with cells (106, 111, 116) in the wireless network, the method comprising: for each of a plurality of cells in the wireless network, obtaining (1210) first time-series data representing a plurality of key performance indicators, KPIs, at a first plurality of past time points; applying (1220) a multi-layer forecasting model to the first time-series data to determine second time-series data representing the plurality of KPIs for each of the plurality of cells at a second plurality of future time points; and based on the second time-series data, determining (1240) respective probabilities of occurrence for a respective plurality of different performance issues, associated with the plurality of cells, during one or more future time periods that include the second plurality of future time points; the method further refers to a corresponding network optimization function, a network optimization node and corresponding software.