I usually check aviation weather enroute on my Iphone when I do a long ride. Terminal Aerodrome Forecasts (TAF's) are the most specific and accurate reports that are available for specific airports and weather reporting locations. You can look them up for free on airnav.com or a host of other sites. You have to know how to decode them but it's easy once you learn how.
I think most people will get a better outlook on the weather at
www.noaa.gov. Simply go to the site, type in a city/state and you get simple forcast descriptions, radar and satelite. Click on the Hourly Weather Graph option and you see serveral days of all the important statistics on a rolling graph. It is in plain english and has lots of useful graphics, particularly the current radar pages.
One thing I do use to get right-now, right-here data is the AWOS (Automated Weather Observing Station) data over the phone. A link to the phone numbers is
http://www.airportview.net/awos.php. You still need to know the format and some of the secret coding, but nothing is better at letting you know exactely what is happening in real time. I ride in Colorado and the ones over the mountain passes are great since the weather can be way different at 12,000' than in the valley below. (When I am flying i actually find it easier to use the phone rather than tuning the NAV. All the stations are entered into my contacts list.)