Ed Joyce and Alex Hales both made centuries on another run-laden day at Hove.
Joyce’s unbeaten 164 helped ensure Sussex avoided the follow-on in the morning but a breathtaking 167 from Hales put Nottinghamshire very much back in the driving seat by the close of play.
The England international’s first Championship ton for almost two years was scored at a rapid rate and enabled Notts to declare on 336-4, a lead of 433.
Chris Nash and Luke Wells safely saw out the final four overs without alarm as Sussex closed on 29-0, requiring another 405 to win.
The morning was very much Sussex’s as Joyce and Jon Lewis comfortably added the 33 extra runs they needed to avoid the follow-on.
The pair were largely untroubled by Stuart Broad and Peter Siddle as they took their partnership – which stood on 54 overnight – to 117 before Lewis finally fell for 38.
Matt Hobden was then trapped lbw by Andre Adams who finished with figures of 5-65 leaving Joyce unbeaten on 164.
With the forecast for tomorrow looking grim Notts knew they needed quick runs to set up a declaration and Hales provided them.
He did receive a reprieve when he was dropped by Rory Hamilton-Brown at second slip on 32 but made the most of it.
Hales reached his 50 off 47 balls and went on to his first hundred in the Championship since August 2012 from a further 49 deliveries.
Once into three figures he really stepped up the pace, thrashing his next 50 in just 27 balls, including four huge sixes.
He finally perished when he attempted to hit Chris Nash for a second maximum in a row and was caught in the deep by Luke Wright.
Nobody else was able to match Hales’ aggression with Michael Lumb falling for 13 when he was superbly caught by Hamilton-Brown in the slips off Hobden and Samit Patel caught behind off Jimmy Anyon for 19.
The scoring rate continued to drop and Notts delayed their declaration – somewhat puzzlingly considering play is likely to be badly disrupted by the weather tomorrow - until shortly before the close on 336-4 with James Taylor unbeaten on 65 and Riki Wessels 20.
That left Sussex with only four overs to negotiate and Nash and Wells went on the attack to take 29 runs from them – meaning 450 runs had been scored in the day.