The 22-year-old left-hander made 101 to help his side progress their first innings from an overnight 282 for six to 448 all out, Luke Fletcher striking 51 and Tom Moores 46.
Skipper Tom Abell (three for 84) was the most successful bowler in a depleted Somerset attack, badly missing England’s Craig Overton and the injured Lewis Gregory.
By the time bad light ended play at 5.50pm, the home side had collapsed to 87 for seven and were staring down the barrel of a follow-on. Fletcher took the first four wickets and ended the day with figures of four for 21 from 11 overs.
Somerset had one of their poorest mornings of the season, the bowling lacking penetration, and not helped by some sloppy fielding, which saw chances go down.
Patterson-White was in the form to capitalise, quickly moving from his overnight 46 to a half-century off 44 balls, with 10 fours.
Moores brought up a century stand for the seventh wicket, made from 111 deliveries, and had added 20 his overnight 26 when edging a defensive shot off Tom Lammonby to wicketkeeper Steve Davies.
Patterson-White batted with an assurance that belied his previous highest first class score of 73, adding to his boundary count with some meaty blows.
He was rarely troubled in moving to three figures with a single off Jack Leach, punching the air in delight as he made his ground at the bowler’s end.
It was 381 for eight when Patterson-White’s immense contribution ended with him being pinned lbw on the back foot by the left-arm spin of Leach.
Brett Hutton weighed in with a useful 31 before skying a catch to give Abell his third wicket and Fletcher ensured there was no respite for the home attack with a 90-ball fifty, including 7 fours and a six.
All the momentum was with Notts when Fletcher was last man out and soon he was making life tough for the Somerset batmen, trapping Davies lbw with the final ball of the opening over.
Abell and Lammonby were given a tough examination either side of tea, which was taken at 11 for one.
The final session saw Abell break loose with some attractive shots. But, with the total on 51, Lammonby, who had battled his way to ten, edged a catch behind to give Fletcher a second wicket.
Abell followed for 35 in the same over, also nicking a ball through to wicketkeeper Tom Moores.
Before Lewis Goldsworthy could reach the wicket, the floodlights failed, forcing the umpires to suspend play for bad light.
It proved a temporary reprieve for Somerset as play soon resumed, with Fletcher and Moore combining again to dismiss Goldsworthy before Dane Patterson sent back James Hildreth leg-before.
When Roelof van der Merwe fell in similar fashion to Hutton and Tom Banton was caught behind off Patterson, Somerset were in disarray.