Maintaining information in working memory normally happens in dynamic environments, with a multitude of distracting events. This is particularly evident in the auditory system, for example, when trying to memorize a telephone number during ongoing background noise. How relevant to-be-memorized information is protected against the adverse influence of a temporally predictable distractor was the main goal of the present study. For this purpose we adapted a Sternberg task variant established in the visual modality, with either a strong or a weak distracting sound presented at a fixed time during the retention period. Our behavioral analysis confirmed a small, albeit significant deterioration of memory performance in the strong distractor condition. We used a time-generalized decoding approach applied to magnetoencephalography (MEG) data to investigate the extent of memory probe-related information prior to the anticipated distractor onset and found a relative decrease for the strong distractor condition. This effect was paralleled by a pre-distractor alpha power decrease in the left superior temporal gyrus (STG), a cortical region putatively holding memory content relevant information. Based on gating frameworks of alpha oscillations, these results could be interpreted as a failed inhibition of an anticipated strong (more salient) distractor. However, in a critical analysis we found that reduced alpha power in the left STG was associated with relatively increased memory probe-related information. Our results therefore support the view of alpha power reductions in relevant sensory (here auditory) cortical areas to be a mechanism by which to-be-remembered information is prioritized during working memory retention periods.