Last summer, when I was working on my glider rating, there was training on what is known as the Thermal Index. In a nutshell, it is a numeric representation of air (in)stability and good gliding weather.
While I can't glide during the winter, I CAN combine my background in software development (call it the day job) with gliding and so I wrote an iOS app for Thermal Index. You can get it in the Apple App Store.
It is called TIFree and, yes, it's free. Not many things in aviation are free so enjoy!