Morton a tough test from Second Division strugglers Albion Rovers to force a replay in the third round of the Scottish Cup.
The First Division visitors are unbeaten since August and they made a bright start in Coatbridge as David O'Brien forced goalkeeper Matthew McGinley into an early save with his feet.
Archibald Campbell then fired wide, while, at the other end, Anthony Stevenson's curling effort was held by Morton goalkeeper Derek Gaston.
McGinley again made use of his feet to repel Weatherson and Albion were able to head into the break in front as Stevenson struck in first-half stoppage time.
The defender kept his composure as he slammed home a rebound on the volley from 12 yards out.
However, Morton fought back and Weatherson applied the finishing touch to Michael Tidser's teasing free-kick to restore parity after 58 minutes.