A coolable vane (12) for a turbomachine includes an airfoil (16) with a pair of imperforate ribs (42, 44) that extend laterally across the airfoil. The ribs have suction side termini (52, 56) and pressure side termini (54, 58). The suction side termini chordwisely delimit a segment SS of the airfoil suction wall (28) so that the ribs and the suction wall segment bound an internal plenum (48) for distributing a pressurized coolant spanwisely through the interior of the airfoil. An array of film cooling holes (84) penetrates the suction wall segment and is the exclusive avenue for conveying coolant from the plenum to a working medium fluid flowpath. Accordingly, relatively low pressure coolant may be supplied to the plenum without the risk of backflow or spanwise discontinuities in the surface cooling film. In one specific embodiment of the invention, the suction side rib termini (52, 56) straddle a point of minimum fluid pressure along the suction surface (38) so that positive coolant flow and spanwise continuity of the cooling film can be realized with coolant of the lowest possible pressure and without exposing the suction wall segment SS to excessive stress.