UPDATE: All should be well now. Just download the 1.3 update to Radar In Motion and the maps will work again. Plus, you’ll get all of the features mentioned in the post below. Enjoy and let me know if you have any problems!
The National Weather Service’s server subtly changed something about their website, resulting in Radar In Motion no longer working. I have already submitted the fix as a part of Version 1.3 of the application, which is awaiting approval from Apple. As soon as it is approved, Radar In Motion will work again (and have a lot of new features, too). You will need to download the update when it becomes available. Apologies for the inconvenience.