EN
The paper presents the physical background of the vertical water transformation modeling in the unit quasi-homogeneous forest area with in the winter season. The model structure includes all main processes operating in precipitation (rain and snow) and snow cover interception on forest canopy and forest ground. Special attention has been paid on the kohesion, accumulation, heat and moisture flux processes, evaporation and sublimation from snow cover, change in the water phase and water percolation through snow on the canopy and ground. Basic processes were considered in terms of quasi-homogeneous unit forest area. Each component of the model was described by the mathematical-physics equations. Parameters of the model are the physical characteristics of the plant canopy, ground and air conditions. The concept of the model should be used to simulation of the net precipitation and snowmelt feeding of the unit forest area.