A novel polyhedral cut-fence is proposed to reduce low-elevation sidelobes and maintain smaller radome size for lower-troposphere radars (LTRs). To optimize the design, radiation sidelobes of the LTR equipped with a cut-fence and a metallic circular disk on the top of a hemispheric radome were studied with high-frequency techniques. Special attention has been paid to the effect of the proposed structure on the LTR radiation sidelobes. The obtained results show that a suitable cut-fence can not only minimize radome size but also maintain the desired low-elevation sidelobes. Additionally, the disk on the top of a hemispheric radome needs to be taken into account for accurate far-field prediction. The proposed structure has been used successfully in designing fences and radomes for wind profiler radars throughout the Japanese islands. Our general conclusions may also be applicable to other radar systems.