On another day disrupted by the weather, Welch bowled 14 overs either side of lunch to return 5 for 47 as the visitors lost six wickets in 43 overs.
The 27-year-old right-armer had not taken five in an innings since August 1997, when he took 11 Lancashire wickets at Blackpool, the best match return of his career. Since then he has been troubled by an Achilles injury and endured a season of limited opportunities under the former captain, Brian Lara. "My confidence suffered and I did not bowl well," Welch said. "Brian tended to prefer Dougie (Brown) and Ed (Giddins).
"I tended to bowl outswing and I've tried to develop an inswinger to give the batsmen more to think about."
After Warwickshire added 23 to their overnight score - Brown's 325-minute innings of 20 fours ending on 142 - Northamptonshire started purposefully, Matthew Hayden's first five scoring strokes racing to the fence.
But after Welch struck his first blow, Rob Bailey snicking a catch to first slip, this early promise was undermined. Hayden cut into gully's hands, Mal Loye edged a full drive and 42 for 1 became 66 for 3. Russell Warren and David Sales made good progress, but then Warren played around the Welch inswinger and Tony Penberthy was bowled. When Giddins had Graeme Swann caught at third slip, the visitors were still 20 short of the follow- on.Reuse content