It should be getting a little easier and more reliable to integrate weather data in to your home automation/htpc environment now. NOAA adapted a new policy which includes this:
You can find the rest of the policy by going to the NOAA site.
3. To advance the environmental information enterprise, NOAA will provide information in forms accessible to the public as well as underlying data in forms convenient to additional processing, to the extent practicable and within resource constraints. NOAA will make its data and products available in internet-accessible, vendor-neutral form and will use other dissemination technologies, e.g. satellite broadcast, NOAA Weather Radio, and wireless, as appropriate. Information will comply with recognized standards, formats, and metadata descriptions to ensure data from different observing platforms, databases, and models can be integrated and used by all interested parties.
You can find the rest of the policy by going to the NOAA site.