A numerical approach is proposed and demonstrated for efficient modelling of the thermal plasma behaviour present during a lightning strike event. The approach focuses on events with time-scales from microseconds to milliseconds and combines the finite element method, Magnetohydrodynamics and Similitude theory. Similitude theory is used to scale the problem to require considerably less computing resource. To further reduce the computational burden and to resolve the numerical difficulty of simulating the nearly zero electrical conductivity of air at room temperature an approach based on cold field electron emissions is introduced. Simulations considering turbulent flow have been considered, modelling a test configuration from literature designed to inspect composite material performance and applying an aerospace standard test profile (waveform-B). Predicted peak temperatures (of the order of ~40,000 K) and pressures (of the order of 0.1-0.2 MPa) suggest that the pressure loading during a waveform-B event will have a minimal effect on composite material damage.