The home side closed the first day on 250 for six, having been 238 for three after Nottinghamshire chasing a fourth successive win, had failed to make the desired early inroads in humid conditions.
Warwickshire captain Will Rhodes led the way for his side with a resolute 91 (188 balls, ten fours) before falling to the last ball before tea. Sam Hain (61, 179 balls, five fours) and Matt Lamb (43 not out, 115 balls, five fours) added 75 in 26 overs in the final session before Paterson's burst of three wickets in 14 balls evened the day up again.
Runs never flowed freely, but it was a tight, enthralling day's play amid a lovely atmosphere in the Birmingham sunshine with spectators back in the ground. There were 1,808 Warwickshire members present and they ended the day happy enough having seen their team find some batting resilience - the Bears began this game with fewest batting points of all 18 teams across the three groups.
Nottinghamshire bowled well in the morning, got plenty past the bat and were arguably unlucky not to pick up more than two wickets in the session. The first breakthrough arrived in the 14th over when Lyndon James bowled Rob Yates with his sixth ball. Pieter Malan (17, 42 balls) helped Rhodes add 46 but fell lbw to Steven Mullaney from the last ball before lunch.
On 49 at lunch, Rhodes soon completed his 15th first-class half-century and was within four balls of tea when he turned spinner Liam Patterson-White into the hands of short leg. That ended a partnership of 84 in 35 overs between Rhodes and Hain.
With their side 163 for three at tea, Hain and Lamb batted with patience in the last session to take the score to 238 before Paterson delivered his triple strike. The South African won lbw decisions with inswingers to Hain and Michael Burgess and then moved one away from Tim Bresnan to force an edge into the cordon.
Lamb has returned to Warwickshire's team, along with Craig Miles, in place of Dom Sibley and Olly Stone who have joined up with the England squad. Stuart Broad having also headed off for England duty, Nottinghamshire have brought in Zak Chappell.