David Sales' magnificent double-century helped Northamptonshire to a huge total on a rain-affected third day of their LV= County Championship Division Two match against Gloucestershire.
Sales' sensational knock of 255 not out off 279 balls was the third-highest score of his career and included 36 fours and three sixes as Northants eventually declared on 567 for four, giving them a first-innings lead of 209.
Andrew Hall also contributed an unbeaten 55 off 106 deliveries before Gloucestershire then closed on 31 without loss.
A flat wicket and a poor weather forecast for tomorrow makes a draw the clear favourite.
Northants began the day on 369 for three, 11 runs ahead of their opponents, with Sales resuming on 126 alongside Australia international Cameron White.
Rain began to fall 10 minutes before the players were due out, which led to the entire morning session being wiped out and 33 overs lost as play belatedly started at 2:15pm.
White added 10 to his overnight six before he smashed Craig Miles to Benny Howell at deep midwicket in the fifth over of the day.
But Sales hung around to reach 150 for the 17th time in his first-class career off 172 balls as he and Hall piled on another 170 for Northants' fifth wicket.
The 35-year-old club stalwart then completed the eighth double-ton of his career off 232 deliveries by hammering a four through point off Miles.
It was the first time Sales had struck 200 since August 2007, when he made 219 against Glamorgan at Colwyn Bay, and it helped the hosts to 493 for four at tea, with their lead 135.
Gloucestershire still could not break the partnership in the evening as Sales reached 250 off 270 balls just before Hall completed his half-century off 102 deliveries.
Northants captain Stephen Peters then waved his players off halfway through the 143rd over, leaving Gloucestershire to face 16 overs before the close of play.
Only two were possible before the umpires stopped play for bad light but thankfully the players were back out 10 minutes later with two more overs lost.
Within three balls of the restart, Chris Dent was given a reprieve as he was dropped on two by James Middlebrook at third slip off David Willey.
Dent and Gloucestershire captain Michael Klinger resume tomorrow on 10 and 21 respectively.