Forest fire activity can be strongly influenced by spring moisture status of organic soil layers. Fire managers in Canada account for the influence of overwinter conditions on spring soil moisture using a relatively simple empirical method that considers both soil moisture from the preceding fall and the amount of winter precipitation. There are concerns that this simplified method for tracking overwinter conditions inadequately captures important controls on spring soil moisture for many forested regions, especially as climate change alters winter conditions. The objective of this study was to use virtual experiments to better understand how variable fall and winter conditions influence spring soil moisture. We used five years of soil and weather data collected at a jack pine forest stand near Chapleau, Ontario to calibrate and test a one-dimensional process-based model for simulating heat and water transfer for a forest-soil profile. After successful evaluation against observed soil moisture, we used the model to conduct virtual experiments where we simulated soil moisture response to varying fall and winter conditions. Our simulations suggest that antecedent fall soil moisture conditions have a strong influence on spring soil moisture for years with low and moderate snowpacks; however, years with large snowpacks tended to overwhelm the influence of antecedent fall conditions. Our modelling results can help inform revisions to the current overwintering procedure used by fire managers to better capture dominant influences on spring soil moisture status.