The visitors opted to bat first and lost Kadeer with only two runs on the board, when he was caught by Ian Bell off the bowling of Chris Woakes.
Porterfield (74 n o) and Marshall (94 n o) came to the crease and had put on 172 runs against a Warwicks side which used six bowlers including skipper Ant Botha, before rain stopped play just after 3pm.
An hour and a half later, play did resume and Chris Martin struck to take the wicket of Portfield thanks to a catch by wicket keeper Tony Frost.
Marshall went on to make his century and another rain storm ended play for the day on 190-2.