Version 1.4.4 no longer works with Weather.com due to changes in weather.com's interface. I found the fix by following the "web support" button on the About tab of the City Editor dialog.
After installing Meteorologist (and while it's not running) do this:
1. Download this file to your home directory.
2. Open a terminal window. (It's called Terminal in Utilities.)
mv ~/weather.xml weather.xml
4. Start Meteorologist.