Stuart Broad and James Anderson on opposite sides as Notts bowl out Lancashire for 214.
Surrey's Gus Atkinson takes 6-68 - his first five-for - for 2022 champions against Essex.
Second-placed Hampshire all out for 229 on day one against Warwickshire.
Australia batter Steve Smith makes debut for Sussex at New Road
Jonny Bairstow takes three catches behind stumps for Yorkshire against Glamorgan.
On-loan paceman Henry Brookes takes 6-20 on debut for Derbyshire.
Worcs 188-7 v Sussex
Sean Hunt sends one down on leg stump and Matthew Waits hoists it away over backward square leg for six.
A boundary follows, slashed over the slip cordon, later in the over and Waite has 27 off 24 balls.
Looks like he believes aggression is the way to boost the Worcestershire total.
Somerset v Northamptonshire 137-4
A third interruption of the day and we've had less than 38 overs played. The light isn't good enough to continue.
Frustration for Somerset just as they have clicked into gear...
The stumps are coming out of the ground and the covers are coming on - there is a band of rain approaching too. May in England.
Yorkshire v Glamorgan 135-4
Brilliant from Jonny Bairstow!
George Hill finds the inside edge of Kiran Carlson's bat and Bairstow flings himself to his left to take the catch.
In comes Root to bat at Headingley - not Joe, but his younger brother Billy for Glamorgan.
Notts v Lancs 186-9
Olly Stone is rewarded for a hostile spell of fast bowling with the wicket of Will Williams, who backs away and carves one to third.
Lyndon James takes the catch in the deep - the third one of real quality by Nottinghamshire fielders in this innings.
In comes number 11 James Anderson, who I'm sure will be loving the prospect of facing Stone in this mood.
But he did make 81 in a Test against India at Trent Bridge in 2014, so who knows?
Derbyshire v Leicestershire 122
Job very impressively done by Derbyshire as they wrap up the Leicestershire first innings in only the 40th over.
Josh Hull tries to lift his bat out of the way of a ball from Sam Conners but it makes contact with something and the umpire gives him out caught behind.
Conners has 2-53 but the bowling plaudits go to loan recruit Henry Brookes who returns a career-best 6-20 from 12 overs.
Somerset v Northamptonshire 137-4
Yes they can wrestle some momentum.
Lewis Gregory is in the zone and, as he did a few moments ago, he angles in another to the left-hander, the off-balance Saif Zaib takes a hoik but the hint of swing means he can only get an inside edge onto his stumps.
He trudges off... but the other players follow him. We have another break in play...
Hampshire 120-6 v Warwickshire
Come for the bowling masterclass, stay for the cover drive showcase.
Chris Rushworth has had it all his own way for a little too long and James Vince reminds him he's there with a gorgeous square drive before a slightly straighter one from the very next ball. He holds the pose, perfectly balanced. Take notes, kids.
Yorkshire v Glamorgan 128-3
More sedate progress from Marnus Labuschagne at Headingley, but he's done a fine stabilising job for his Glamorgan team after the peril of being 1-2 early on.
The Australia batter reaches his fifty off 142 balls.
Notts v Lancs 181-8
Tom Bailey, backing away so far into the leg side against Olly Stone that he's almost in the first row of the stand at Trent Bridge, slice one through the slips to the boundary.
The next ball, he stays still and gets hit on the left shoulder by a brute of a bouncer.
Bailey responds to that by crashing a full ball through mid-on to the fence.
A thrill a minute.
Worcs 160-7 v Sussex
Image source, Getty ImagesThe perfect yorker.
Adam Hose is caught flat-footed and cannot get the bat down in time as Henry Crocombe knocks out his off stump.
Hose faced 88 balls and hit nine fours. Joe Leach is his replacement.
Somerset v Northamptonshire 126-3
Image source, Rex FeaturesIt's the big one. Angled in to the left-hander by Lewis Gregory with a touch of swing and Ricardo Vasconcelos edges to Craig Overton who takes a fine two-handed catch at second slip tumbling to his left.
Feast and famine for the hosts at Taunton, but can they finally wrestle some momentum now? Rob Keogh joins Saif Zaib.
Somerset v Northamptonshire 126-2
13 scoreless balls first up for Saif Azib but Craig Overton sends a loose delivery down the leg side which Azib helps to the fence to get off the mark with a gimme.
Ricardo Vasconcelos has scored 13 boundaries in his 70 from 100 balls.
Somerset have not helped themselves today. Particularly when they have two lefties at the crease, as they do now.
Yorkshire v Glamorgan 113-3
Yorkshire seamer Ben Coad, who removed both Glamorgan openers this morning, has gone off the field with an injury.
Bad news for the hosts.
Derbys v Leics 107-9
Henry Brookes now has six wickets at the Incora County ground after Michael Finan was well caught at short leg by Matt Lamb.
No doubt someone will tell us the best figures by a Derbyshire debutant to save us trying to look it up.
Hampshire 109-6 v Warwickshire
After a longgg delay the finger goes up and Chris Rushworth has his second lbw in four deliveries. Liam Dawson is back in the hutch for no score after some more late movement from Rushworth to get one to straighten up on him.
Ian Holland is the latest to join James Vince. Hampshire are 26-5 since the ball before lunch.
Essex 125-3 v Surrey
Tom Westley tries to pull a short ball from Sean Abbott and is perhaps a shade fortunate as it just misses the edge on its way through to Ben Foakes.
The next one barely leaves the turf after pitching, but Westley survives again - that's not the first time we've seen the pitch behave in that way today.
Somerset v Northamptonshire 117-2
And on we go... going to be that kind of day.
Ricardo Vasconcelos is going to have to work for everything he gets today, he's unbeaten on 65.
Notts v Lancs 155-8
Tom Hartley is the latest Lancashire batter to fall and Brett Hutton has a five-wicket haul.
Hartley pulls one to deep square leg and Ben Slater dives away to his right to take a superb catch.
Lancashire reeling on 155-8.
Hampshire 109-5 v Warwickshire
That's the ninth time Chris Rushworth has ousted Ben Brown. He gets one to straighten up on Brown and thuds the pads.
The finger eventually goes up and Hampshire's momentum stalls further. From 83-1 to 109-5.
Liam Dawson joins James Vince in the middle to face this fired-up Bears attack in useful conditions.
Somerset v Northamptonshire 117-2
The covers are being rolled on at Taunton as it continues to drizzle in the gloom. No immediate prospect of a swift return, unlike this morning, I'm afraid.