All gridded wind output from NCEP from RUC or other models is grid-relative for direction. The speed is true, and is not affected by map-scale factor issues.

To get lat/lon-relative u/v, you must rotate the winds by the following angle: 0.422618 * (longitude - long_true), where long_true is -95.0 (95 deg W) and longitude is at each grid point. The 0.422618 factor is for the Lambert conformal projection used for the RUC.