|Warrington (10) 20|
|Tries: Hughes, Penny, Dwyer Goals: Gidley 4|
|Widnes (12) 18|
|Tries: Mellor, Whitley, Runciman Goals: Hanbury 3|
Warrington Wolves narrowly beat local rivals Widnes Vikings to reach the Challenge Cup semi-finals.
Kurt Gidley's late goal gave the hosts victory following a tight second half.
Widnes led 12-10 at the break through converted tries from Joe Mellor and Matt Whitley, with Jack Hughes and Kevin Penny scoring for the hosts.
Brad Dwyer crossed to put Warrington back ahead but Charly Runciman levelled the scores at 18-18 before Gidley's late penalty settled the tie.
Eight-time winners Warrington join Wakefield in the last four, with Hull FC, Catalans Dragons, Wigan and Castleford looking to join them on Saturday.
Greasy conditions made for an error-strewn game at the Halliwell Jones Stadium, with the game becoming stretched as the second half wore on.
Dwyer's close-range score gave the Wolves the initiative after the break but Runciman finished a well-constructed move to drag Widnes level with 15 minutes left.
However, the Vikings were punished when Hep Cahill was offside from a knock-on by Rhys Hanbury and the visitors had no reply to Gidley's kick from the tee.
Warrington, who had centre Ryan Atkins taken to hospital for assessment following a first-half concussion, will find out their semi-final opponents when the draw is made on Saturday following Wigan's tie with Castleford (17:30 BST, live on BBC Two).
Warrington: Ratchford; Russell, Evans, Atkins, Penny; Gidley, Sandow; Hill, Clark, Westerman, Currie, Hughes, Westwood.
Replacements: Dwyer, King, Bailey, Cox.
Widnes: Hanbury; Thompson, Runciman, Bridge, Ah Van; Mellor, Brown; Cahill, White, Buchanan, Houston, Dean, Leuluai.
Replacements: Whitley, Manuokafoa, Dudson, Heremaia.
Referee: James Child