Considering the forecasted data to be released tommorrow, would it be best to lock today or tommorrow on a 30 year fixed?

At this point, it is too late unless you have access to 24 hour lock.  If you don't, at 830am eastern time the non farm payrolls and unemployment rate will be released.  Expectations are for a loss of about 350,000 and a rate of 9.8%.  for rates to hold steady or improve, they will need worse then expected numbers.

Unfortunately more people than expected lost their jobs.  This should be good for rates, so a bittersweet victory.