Within the framework of Bohm's reformulation of quantum physics we revisit the activated dissociation of hydrogen molecules at metal surfaces. The quantum-mechanical force, which accounts for most of quantum effects in the method, and is caused by nonlocal, topographical properties of the wave function, is computed using time-dependent wave packets obtained using conventional, spectral methods. Driven by a combination of the classical force together with the quantum force, trajectories carrying probability density either succeed in overcoming the barrier for dissociation or are scattered back into the gas phase. The Bohmian picture for the dissociation process has enabled us to develop a novel mechanism to account for vibrationally enhanced molecular dissociation. This is relevant to the recently observed promotion of dissociation of very highly vibrationally excited NO molecules at Cu surfaces.