Your right, you did explain the timeout. It was just as I started making the connection with the scanning modules on the firewall the first thing that popped into mind was the possibility of a time out of a few milliseconds. I know that scanning the traffic doesn’t take 30 seconds; if it did anything I did over the internet would be noticeably slower. As an example when I checked the url you posted above the results came back in a second or two. If the filter was slowing the traffic down that bad, the results would’ve taken considerably longer to show.
I have not received any emails from Wunderground today, and I would have by this point if I exceeded the call limit. I just checked my Wunderground page and the usage looks about right for a call every 15 minutes. So I believe that isolates the issue to scanning modules of the UTM, what that is I don’t know yet. I’ll do some digging this evening to see what else I can figure out.