Status update:
I talked via email with John Celenza of WeatherUnderground and the issue with the WU-forecast.php script was caused by an IP block by WunderGround on my server's IP address. They have kindly removed the block, and the script works again.
I did do an update to WU-forecast.php V1.28 tonight to add the ability to follow the 301 redirect to their block.asp page, and cache the contents in the cache file. If it happens that you find no forecast, even after doing a ?force=1 to force a cache refresh, then check the contents of your cache file (do a view source on the page to find the name/location of the file), and in the file will be the text of the block page .. you can use the IP address there to contact WU to ask the block be removed.
I also changed the request to include a User-agent: PHP,WU-forecast.php,saratoga-weather.org so they can identify that the request was made by the WU-forecast.php script (and that they should contact me for questions).
Sorry for the alarm .. in short:
1) WU was blocking some IPs for excessive traffic (I think)
2) The script couldn't get past the block, so stopped offering you a forecast.
3) the updated script V1.28 has diagnostics to help you put a request to WU to unblock if it happens to you
I am working (and about 80% finished) with a WU API JSON script and will release it later, but the WU-forecast.php can live on to serve

Best regards,
Ken