San Diego manager Bud Black said that Grandal will serve as the designated hitter Wednesday and then catch for the Storm on Thursday. Lake Elsinore is situated about one hour north of San Diego.
Grandal has been on the disabled list since July 31 with a strained right oblique muscle, an injury that occurred taking a swing on July 30 against the Reds.
Grandal, a switch-hitter, has reported no pain while throwing to the bases and taking batting practice in both the indoor cage at Turner Field and on the field the last two days.
At the time of the injury, Grandal was hitting .312 with five home runs and 15 RBIs in his first month in the big leagues.
There's a chance that Grandal could be reinstated from the disabled list before or during a weekend series against the Giants at Petco Park that begins Friday.