I am almost certain if you get drug tested they will include marijuana. It is part of the NIDA-5, the most basic multiple panel (panel meaning controlled substance) drug test. NIDA-5 includes THC, cocaine, PCP, opiates, and amphetamines. They can test for many more if they like but you can almost be certain THC will be included and not overlooked.

You will have a little more than a month for your body to get clean. The only things that can help your body get clean is time, aerobic exercise, and a low fat diet with soluble fiber. If I understand correctly, you will be starting your jail time soon so this things may be hard to accomplish. Most people get clean in about 30 days or less but some chronic smokers may take 30+ days to get clean. It looks like they are going with the assumption you should be clean because you are locked up.

To answer your question further can you give your height and weight and a more complete smoking history?

BTW it isn't so much "trace" amounts. Through research scientists and doctors have determined thresholds on drug tests that correlate to levels that indicate use and not passive exposure and these thresholds are used across the board in most cases. I hope that makes sense.