Reaching out here for basically a 'Product enhancement' so as to help client leverage the Alerts functionality(within Analytics) better.
The ask is to trigger an alert(notify a registered user on the client side) when the current day's data falls by more than a particular percentage(say 30%) when compared to the same metric number for the same day last week. For example: We would like to compare today's visits data(Tuesday) with last Tuesday's data.
Based on my understanding, this cannot be configured based on the current set of available configurations. Feel free to add to this if necessary.