STAR measurements of dihadron azimuthal correlations (Δϕ) are reported in midcentral (20–60%) Au + Au collisions at √sNN=200 GeV as a function of the trigger particle's azimuthal angle relative to the event plane, ϕs=|ϕt−ψEP|. The elliptic (v2), triangular (v3), and quadratic (v4) flow harmonic backgrounds are subtracted using the zero yield at minimum (ZYAM) method. The results are compared to minimum-bias d + Au collisions. It is found that a finite near-side (|Δϕ|<π/2) long-range pseudorapidity correlation (ridge) is present in the in-plane direction (ϕs∼0). The away-side (|Δϕ|>π/2) correlation shows a modification from d + Au data, varying with ϕs. The modification may be a consequence of path-length-dependent jet quenching and may lead to a better understanding of high-density QCD.