This study investigates a rare return-flow snowstorm that occurred in the northern Shandong Peninsula from February 20 to 21, 2024. By integrating conventional observations, reanalysis data, WRF model sensitivity experiments, and HYSPLIT backward trajectory tracking, we systematically analyze the spatiotemporal characteristics, circulation background, topographic influence, and moisture sources of the snowstorm, aiming to reveal the physical mechanisms underlying the local topographic effects on the return-flow snowfall. The results indicate that this snowstorm occurred under a typical return-flow circulation pattern. Cold air at 925 hPa moved southward across the Bohai Sea and the northern Yellow Sea, forming a cold tongue, while a moist southwesterly flow at 700 hPa transported abundant moisture. The configuration between the upper- and lower-level flows created favorable vertical wind shear and upward motion. The WRF control experiment effectively reproduced the spatiotemporal evolution of the snowfall. Topographic sensitivity experiments demonstrate that the hilly terrain of the Shandong Peninsula, enhanced vertical moisture transport and condensation through dynamic lifting, triggering significant vertical ascent and a closed secondary circulation cell on its northern slope. This directly enhanced snowfall in the region from Yantai to Weihai. The effect markedly weakened when the terrain height was reduced. Moisture trajectory analysis further quantitatively identifies two key moisture channels: one originating from low latitudes, contributing approximately 67.16% of the moisture via the mid-level southwesterly jet, and the other stemming from high-latitude cold air, which absorbed evaporated moisture from the warm surface of the Bohai Sea, forming a low-level cold, moist flow that contributed about 32.84%. This study confirms that during return-flow snowstorms, the topography of the Shandong Peninsula exerts a significant local enhancement effect on heavy snowfall in the northern peninsula through dynamic lifting. The findings can provide references for forecasting, warning, and mechanistic research of similar snowstorms in the peninsula region under analogous synoptic conditions.