Replacing prefs is really about re-naming them. Before you do that, however, it will save lots of time if you make a screen shot of every single preference panel that the app has.
WC has over a dozen separate pages of prefs. And there are dozens of .plist files. The one you don't make a screen shot of is the one you'll forget how to set.
Secondly, make sure you know/find every .plist the app uses. The basic one(s) should be in your User/Library/Preferences directory. Be aware that WC also has a dozen or so in User/Library/WeatherCatData. Additionally, there may be a coupl in User/Library/Application Support/WeatherCatTemp. They usually have the name of the developer and/or the name of the app in what is basically a reverse url format: com.apple.Mail.plist, com.trixology.weathercat.plist, etc. but sometimes it is something like WeatherCatDaily.plist,
1. Shut down the app that uses the Pref(.plist). If you don't quit the app, it will probably just re-create the old plist info when you do quit it next.
2. Change the name of the .plist to something really creative... like adding "-OLD" to the end of the name. Probably best to add it at the end of the name and just before the ".plist" part. That will keep it in the same relative position in your files and make it easy to find once you determine if it was the problem.
3. Restart the app and start re-creating the prefs settings... If you have a fast drive, it won't hurt to make a complete restart of the OS, but that's not usually necessary.
4. Recreate all the prefs the way you want or had them.
Be very careful when entering the info. I found a problem recently where I had typed in the url for my camera as
http://10.0.1.10/live/0/jpeg.
jpeg when it should have been:
http://10.0.1.10/live/0/jpeg.
jpg See the one letter erer?! I blame it on Microsoft because they never had a really effective way for apps to know which files they should open because they limited suffixes to 3 letters. Apple used four, plus they used Creator and Type values... or at least they did until they caved in to the M$ hoards.