The origins of these simulated extreme updrafts are investigated. Preliminarily, it appears likely that the extreme updrafts are dynamically forced, in association with large near-surface intensification of small scale low-level vortices. The simulated updrafts are also compared with dropsonde-observed extreme updrafts in terms of structure, magnitude, and location. The sensitivity of low-level updrafts to boundary layer parameters are explored through multiple simulations with varying drag coefficient (Cd) and boundary layer depth. When the boundary layer depth is forced to be reduced to 80% of that of the control simulation, the maximum updrafts are found 500-750 m lower, and are stronger. In contrast, when Cd is reduced to 80% of that of the control, the maximum updrafts are weakened by several m/s, while the height of the maximum is unchanged.