I am not sure how to do so — what kind of connection interface your weather stations provides? If it provides an HTTP interface, it should be possible, at least by modifying the firmware, to have OS directly talk to the weather station. Also, by default the OS firmware queries the weather server once every hour, and the frequency can be easily reduced by changing one number in the firmware. You should also check your weather station’s update frequency to see if there is a way to reduce the number of times it sends data to wunderground over a day.