Dear CCWxWatcher, Stu, Blick, and WeatherCat cautious sys-admins,
For this reason, many of us duplicate the com.trixology.weathercat.plist file (once you know it is good) and store it for a future need to replace the old one. It is much easier to have a good working copy of that file than to have to go back in and remember to put all of your settings back the way you want them. This will NOT help you this time, because you need to make sure you have a good plist file first.
There is no guarantees, but if you run Time Machine (or some other backup software that can retrieve a single file,) you could try replacing
com.trixology.weathercat.plist with an older version of this file before your problems started. That is a lot less hassle than having to put all your preferences back into WeatherCat. I also have made a separate backup copy of the
com.trixology.weathercat.plist file because this happening more often since macOS 10.10 Yosemite.
If you attempt to restore this file from backup, you must still follow Blick's instructions to the letter. If you don't, you will simply have macOS put back the corrupted information into the file you had gone to so much trouble to restore from backup.
Cheers, Edouard