Jeremy Jackson and Jesse Homan collected maiden six-fors and Jason Snare missed a maiden ton by a whisker in an eventful first day of round 15.
Mowbray batted first at Riverside and Snare opened proceedings by hitting Sam Lockett for six on the first ball of the day.
Snare looked impressive but lost wickets all around him as Lockett (3-31) and Homan ensured Sam Freeman (13) would be the only other Eagle into double figures.
The ex-Longford batsman reached 99 before a direct hit from Blues coach Lyndon Stubbs caught him by surprise running to the striker's end.
Snare was the last wicket to fall as the Eagles were dismissed for 152.
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"He'll be disappointed but he really did bat well," Eagles coach James Storay said.
"I think he's set himself a standard now for how he can go about batting time - he batted for just about two sessions and he's starting to know his game a little bit more now he's playing turf cricket."
Storay (2-23) removed both openers early in Riverside's innings before Matthew Kerrison (60) and Ramesh Sundra combined in a 65-run stand.
Both would fall to Ben Spinks (2-21) late in the day as the Blues finished day one 4-88.
"I think we've definitely made enough inroads to make a game of it next week," Storay said.
For the Blues, Homan finished with a career-best 6-53 to go with a catch in the field.
"Our bowlers bowled really well, [especially] Sam Lockett and Jesse Homan," Stubbs said.
"It was really pleasing for Jesse to get the reward, he'd been consistently our best bowler and he bowled really well today."
Homan was sent out as a nightwatchman late in the day after Kerrison had his bails dislodged in the third-last over.
Kerrison's 72-ball knock was his best score of the year to date and featured a beautifully-timed hook that cleared the boundary at deep square leg.
"It was good for him to be back in the runs - he's been batting well, he just hasn't been converting," Stubbs said.
"At 4-88 if we start well we can knock off the 150 next week and have a good crack at them."
WESTBURY has the upper hand after a topsy-turvy day at South Launceston.
The Shamrocks reached 1-133 early in the frame after Matthew Battle (37) and Nathan Parkin (64) combined for a 75-run opening stand.
But the venomous leg-spin of Jeremy Jackson (6-62) brought South back into the game as the president led from the front, almost single-handedly reducing the Shamrocks to 7-166.
It took a crucial knock of 46 from number 10 Joel Lloyd to reach 251 all out and swing the momentum back Westbury's way in the day's final 20 overs.
Kieren Hume and Nick Spencer both took two wickets as the Knights stumbled to 5-62 at stumps.
Unbeaten pair Sean Harris and Nathan Philip (28 not out) and the returning Brodie Jarrad represent South's three remaining recognised batsmen heading into day two.
"We were a little bit up and down throughout the day, but it's a pretty good position to be in, I'm pretty happy with where we're at," Westbury skipper Dan Murfet said.
"It was good to see Nathan go on and put a decent score out there, he's been showing some really promising signs since coming back from a knee injury and he batted really well today in tough conditions - it was spinning a lot quite soft and really slow.
"We were a little bit unfortunate we had a collapse in the middle which is what we're trying to really get away from now, but thankfully the tail wagged a bit and Lloydy made a few runs - we know he's really capable as an all-rounder.
"We bowled really well in the last session - Lloydy was able to help give us a bit of momentum and we were able to take that out with the ball and put some balls in some good areas and take some good wickets."