You could be busted.
When I took training for that sort of thing (used to take people to drug tests at my former employer) I was taught that 30 days can be the expected duration you will test positive for weed.
How do you know you have a test tomorrow? Pre-employment? Condition of probation or parole?
If it's a random, your company has a really lax and terrible drug program.
How Long Can Marijuana Be Detected?
Some THC metabolites have an elimination half-life of 20 hours. However, some are stored in body fat and have a elimination half-life of 10 to 13 days. Most researchers agree that urine tests for marijuana can detect the presence of the drug in the body for up to 13 days.
However, there is anecdotal evidence that the length of time that marijuana remains in the body is affected by how often the person smokes, how much he smokes and how long he has been smoking. Regular smokers have reported positive drug test results after 45 days since last use and heavy smokers have reported positive tests 90 days after quitting.