Alert based on daily trend

I have regular alert for CPU, Mem and disk with a fixed thresholds. I am collecting data every 5 minute and my value for variable period is 7min and every is 5 min.

If i want to generate a alert my system behave in different day than day before, basically i want to compare current value and previous values for same time and if there is significant difference create an alert.

Could you point me to the right directions