MSP430G2553 help

I'm using this microcontroler with the ina219, I want to take voltage from a 20x20 solar cell and store that data. I want to read that data later on. I will take messurments every 5 minutes for 5 hours, Each messurment is stored on the flash. My question is: Will the flash erase the data after i power off the circuit, is using a SD card a good idea, or is this even possible?
Thanks upfornt.