Wifi connection dies about once a day

I've been using Yosemite for several months and have kept it fully updated. All of a sudden starting about a week ago, my Wifi connection will go dead on my Mac Pro running Yosemite 10.10.3. My router is fine and all other computers and devices stay connected during this problem.

The icon in the menu bar is normal, however when I click on it, no Wifi networks are shown at all. It normally shows the two nearby networks, and at the very least, it would show the one it's connected to. So somehow the icon is showing I'm connected while no networks appear underneath and I cannot access my LAN or Internet. I even have the "Turn Wifi Off" menu option, however, when I look in the Network Preferences, it shows that I am not connected with a button that says "Turn On Wifi". It will not respond to this button no matter how many times I click it. Eventually, the menubar icon turns hollow, properly indicating no connection. I still cannot turn on Wifi from the menu bar or the Network preferences. The only way to get connected is to reboot the computer. Logging out/in the user does not work either... must reboot.

This is happening at random times and mostly late at night. In the last week, it's happened about five times already. There does not seem to be any steps to reproduce the problem.

What the heck is going on? I never had any Wifi issues before a week ago and I have not recently update any software. I thought 10.10.3 was supposed to fix all the weird Wifi issues.

Is there a preference file I can delete to start over with fresh network settings?

Thanks.