Increasing variability in the manufacturing process and growing complexity of the integrated circuits has given rise to many design and verification challenges. Statistical analysis of circuits and current source based gate delay models have started to replace the conventional static timing analysis which uses lookup tables for gate delays. In this paper we develop a statistical current source based gate model. We use accurate analytical models for representing the parameters of the gate model as functions of process parameters. Using the proposed statistical gate model, the gate output signal is generated and modeled as process dependent variational waveform. We present a compact model for representation of the variational signal waveform. The proposed waveform model can accurately generate the signal waveform at any process corner for accurate timing analysis. We generated the prosed model for gates of a 90nm industry library and validated with SPICE simulations. Our model for logic gates and variational waveforms showed very good correlation with SPICE. The maximum error across all validation experiments was close to 3%.