After losing the toss, Northland were sent into bat on a very green Cobham Oval wicket, which caused the ball to nip around.
"But the guys came out with a sound game plan of what we wanted to achieve and they executed that well with clear intent, reaching 356 all out," Cunis said.
Ian Page top-scored with 80 runs, and put on a partnership of 117 with Nic Breslin in 23 overs. Batting at No6 and No7 respectively, Breslin and Bert Horner both reached half centuries, while Craig Coffey (39) and Brad Kneebone (45) also chipped in.
Counties went into bat late on Saturday, and made a definitive start, reaching 76/1 at stumps. After such a positive start, Northland's initial poor bowling could have cost them dearly, Cunis said.
"The bowlers knew in no uncertain terms what they did on Saturday was not good enough ... the team got a tune-up and it was made clear what our intentions were for Sunday," the coach said.
Northland's bowlers returned on Sunday with vigour, preventing Counties' batsmen from making any worthwhile stands - no one got past 50 - and Counties fell 27 runs short of their target when the game was called off, Cunis said.
Cody Andrews bowled with good pace, taking 3-81 off 22 overs, while Ryan Smith took 3-58. Matt Taylor and Tom Herman also claimed wickets two each.
Northland play their final Fergus Hickey two-day match of the season against Waikato Valley at Cambridge, in two weeks.