Widnes 12-10 up at the break through Joe Mellor and Matt Whitley
Brad Dwyer scores for hosts after half-time but Charly Runciman hits back
Late Kurt Gidley goal wins it for Warrington
Warrington join Wakefield in last four
Warrington 10-12 Widnes
A lengthy delay while video referee Phil Bentham looks at a possible try for Warrington's Ben Currie.
On-field official James Child signalled "no try", deeming Currie had lost control of the ball and Bentham finds nothing to disagree with that view.
Warrington 10-12 Widnes
Warrington, trailing by two points, are in the ascendancy at the start of the second period.
Chris Sandow fancies a dart to the line from close range but is held up by a dogged Widnes defence.
Meanwhile, BBC Sport's touchline reporter Tanya Arnold reports that Warrington's Ryan Atkins is on his way to hospital after receiving a knock to the head in the first half. We wish him well.
#bbcrl
As the players begin the second half, feel free to get in touch with your thoughts on tonight's game using #bbcrl on Twitter.
HT: Warrington 10-12 Widnes
Image source, Getty ImagesAway from the Challenge Cup, there's one big Super League recruit that you may have missed in the past 24 hours.
Frank-Paul Nuuausala has joined Wigan from NRL side Canberra on a three-and-a-half-year deal.
The 29-year-old New Zealand international, who played for the Kiwis in their 2013 World Cup final defeat by Australia, is expected to link up with the Warriors in the next few weeks.
HT: Warrington 10-12 Widnes
Four more sides will compete for the last two Challenge Cup semi-final spots tomorrow.
Super League leaders Hull FC host fourth-placed Catalans Dragons (13:30 BST) in what is perhaps the pick of the four last-eight ties.
Then at 17:30 BST, Wigan play Castleford in a game you can watch live on BBC Two.
I'll be on duty bringing you live text commentary of both matches on the BBC Sport website and app.
With that in mind, I promise I'll get an early night tonight.
HT: Warrington 10-12 Widnes
Jamie Peacock
Former England captain on BBC Two
The early errors from Widnes were caused by Warrington's aggressive defence. As the Wolves started to drop off, Widnes came back into the game.
Widnes were ineffective for the first 20 minutes and got back into it when Warrington weren't able to defend in the same way.
HT: Warrington 10-12 Widnes
Warrington half-back Chris Sandow: "Widnes are trying to turn us with their kicking game, so hopefully we can do that to them in the second half. We're overplaying to hand quite a lot but I think we'll settle down in the second half."
Widnes half-back Kevin Brown: "We're happy with parts of that half. We're ahead on the scoreboard but there's plenty to work on. We've made errors on the ball but if we fix that we've got a good chance of winning."
Warrington 10-12 Widnes
Image source, SWPIX.comWell that first half took a little while to get going, but it's amazing what a couple of quick tries can do.
Warrington led early through Jack Hughes, but Joe Mellor and Matt Whitley crossed in quick succession to put the Vikings in front, and they still lead by two points despite Kevin Penny's score late in the first period.
This quarter-final tie is still right up for grabs.
Kevin Penny
Who ordered some tries before half-time? Winger Kevin Penny is over now for Warrington, touching down a grubber kick in the corner.
Video referee Phil Bentham's happy with the grounding, he's happy that Penny is onside from the kick, and Warrington are back in it.
Warrington 6-12 Widnes
Who saw that coming?
Warrington hadn't particularly looked like stretching their lead, but Widnes hadn't particularly looked like responding to Jack Hughes' early score either.
Two tries in two minutes for the visitors have changed that.
Warrington 6-12 Widnes
Jonathan Davies
Former Widnes and Warrington player on BBC Two
The half-break creates it and they keep their composure. What a couple of minutes for Widnes. Manase Manuokafoa and Whitley have made a huge impact.
Matt Whitley, goal Rhys Hanbury
What a turnaround - Widnes lead!
Warrington were caught on the break and they might have thought the danger was over when hooker Daryl Clark denied Chris Bridge a score against his old club, but it wasn't.
Matt Whitley dives over the line and Rhys Hanbury kicks the goal from straight in front of the posts. The Vikings in dreamland.
Joe Mellor, goal Rhys Hanbury
Out of nothing, Widnes get themselves level.
Joe Mellor pounces on an error from Chris Sandow, who spills the ball 15 metres from his own line.
The Vikings half-back kicks the ball ahead and drops on it over the line - try time.
Warrington 6-0 Widnes
Image source, SWPIX.COMWarrington have won both Super League meetings with Widnes this season.
The Wolves won 28-10 in their home fixture in March, before thumping the Vikings 48-16 on their own ground in April.
Can they make it a hat-trick today?
Warrington 6-0 Widnes
Jonathan Davies
Former Widnes and Warrington player on BBC Two
Warrington are completing their sets, building pressure and keeping Widnes in their own half. That has been the biggest difference so far.
Warrington 6-0 Widnes
We have a stoppage in play as Warrington's Ryan Atkins receives treatment following a knee to the head from Hep Cahill.
It looked accidental - referee James Child says as much - but it's placed on report and it's a penalty for the Wolves.
Warrington 6-0 Widnes
In the greasy conditions, Widnes winger Patrick Ah Van slips over before being tackled and then knocks on from the play-the-ball.
It's not really sparked into life yet, this one.
Warrington 6-0 Widnes
Hello, hello, hello. A bit of a coming together between Warrington's Ryan Atkins and Rhys Hanbury of Widnes.
James Child speaks to both, with no further action, and the re-start is a Widnes penalty 20 metres out.
Joe Mellor's kick on the last tackle is gathered superbly by Kevin Penny, who gets Warrington on the counter quickly.
Warrington 6-0 Widnes
This was the scene at the Halliwell Jones Stadium following a heavy downpour pre-match...
Image source, SWPIX.COMWill there be a pot of gold for one side at the end of the rainbow? It's Warrington who have made the better start and have an early advantage.
Warrington 6-0 Widnes
How can Widnes respond to that early concession? Well, they get two quick penalties either side of halfway and a chance to attack the Warrington line.
The Vikings get to within 10 metres but Charly Runciman's flick out wide to Patrick Ah Van is intercepted and the home side survive.