In the context of the random first order transition theory we use an extended mode coupling theory of the glass transition that includes activated events to account for spatiotemporal structures in rejuvenating glasses. We numerically solve fluctuating dynamical equations for mobility and fictive temperature fields which capture both mobility generation through activated events and facilitation effects. Upon rejuvenating, a source of high mobility at a glass surface initiates a growth front of mobility which propagates into the unstable low mobility region. The speed of the front quantitatively agrees with experiments on the rejuvenation of ultrastable glasses, which “melt” from their surface.