The weather report and forecast for BC has very little to do with accuarte forecasting for AC. Even though the distance is short, it is still the ocean and the Caribbean. Even the local forecast for AC on the cable when you get there is iffy. This is one of the drier parts of the year, but the winds, tides, alien vistors, etc. make accuracy fun.
It's difficult to forecast the next half hour at times even when you are standing right on the beach. Or, at least it has been for me, but then.....
You will be just fine.