A last-gasp try by flanker John McPhail and 11 points from utility back Aaron Bramwell gave Patrick Horgan’s side the points to leapfrog Neath in a highly physical encounter.
Only two other matches survived the adverse weather as fourth-placed Cardiff recorded a bonus-point 28-5 win over Maesteg at the Arms Park to move up to third in the table.
Prop Rhys Gill was the star of the show with a hat-trick of tries and wing Ryan Howells second-half score puts Cardiff just one point behind defending champions Neath whose game at Newport was called off.
Maesteg replied through Nathan Trowbridge before ill-discipline cost the visitors dear with three yellow cards.
In the remaining fixture, Leon Andrews scored all Cross Keys points including a brace of tries in a comfortable 18-7 victory over Swansea.
