Hi Ed, and welcome to WXForum.net !
The Davis system is a great one, and you have a couple of choices for weather software that can provide realtime updates. VWS has a WeatherFlash function that will update a website with weather info, and Weather-Display has a function for WeatherDisplayLive that also updates a website in near-real-time. The primary difference is that VWS requires an ASP or PHP script on your site to submit the data to, while Weather-Display will use FTP to submit the weather data file(s) to your website.
WeatherLink doesn't have a function for that for your website (it uploads at 1 minute intervals at the minimum), but with a WeatherUnderground rapid-fire plugin, can update the WeatherUnderground data site at near realtime rates.
You'll need the data logger capability with your Davis system, and it comes with WeatherLink (but you don't have to use WeatherLink .. you can use Weather-Display or VWS instead).
For 'live weather' info, I prefer Weather-Display over VWS for its rich feature set, and while it may be a bit tricky to set up at first due to lots of settings options, it will reliably update your site.
There are two sets of JavaScript available (one for Weather-Display, one for VWS) that allow you to easily insert markups on your website and have the weather variables updated at 5 second intervals.
Both scripts are available on my site (
http://saratoga-weather.org/ ) along with templates showing the markups and other PHP scripts that might be useful for your city's site.
Hope this helps..
best regards,
Ken