RTFDDA-LES extends real-world numerical weather prediction to large-eddy-simulation (LES) scales, with grid sizes down to ~30m. The NCAR WRF-based RTFDDA system is formulated for simultaneously nesting-down from mesoscale to LES modeling scales. The WRF “observations-nudging”-based FDDA is activated on the coarse meshes, which continuously assimilates diverse synoptic and asynoptic weather observations and thus provides accurate boundary forcing to the high-resolution modeling on fine-mesh LES model domains. The WRF-RTFDDA-LES system is described in Liu et al. (2010) in details. RTFDDA-LES will be employed to study and forecasting severe winds in the critical segments of the ultra-high-voltage power transmission lines in complex terrain areas.