Does seem to take a bit to load the weather stats. I could only get the classic stickers to work. You need to modify the code from WU to get it to work in your tagline. In a nutshell you copy out the gif url, paste in profile, then add the img tags to like below.
[img]http://weathersticker.wunderground.com/weathersticker/big2_cond/language/english/US/NY/Rock_Hill.gif[/img]