An investigation on the practical predictability aspects of heavy rainfall event in the east coast states of Peninsular Malaysia was carried out by simulating the 17 December 2014 episode using the Weather Research and Forecasting (WRF). The WRF model was configured with three nested domains of 36 km, 12 km, and 4 km horizontal resolution for 36 h simulations. It was found that the cumulative rainfall amount and the location of the heavy rainfall centre are sensitive to the choices of Cumulus Parameterisation Scheme (CPS). The experiment with a resolution of 4 km that used the multiscale Kain-Fritsch for the outer domains and no cumulus scheme in the inner domain reasonably well simulated the case. Further analysis suggests that the CPS and initialisation gave larger impact to the forecast quality compared to boundary conditions. Grid resolution contributed the least error.