Wind alert is probably the best site/mobile app to use. IT takes the reading directly from actual stations. In some areas they do virtual stations using colleted trend data and actual observations. By far they are the most accurate and will tell you the conditions at the station closest to where you want to fly. Weather channel is probably the best forecast site and the winds will be pretty close to the range given. THey also use historical data to predict trends. Don't use hourly forcasts though except to get a generall idea of the range over a few hours.
I found Wind Alert recently, so I haven't had time to use it much, but the "virtual stations" seem misleading to me. There's one virtual station right smack on my flying field, but its report often seems too good to be true. That virtual station can report 12mph... while being surrounded by physical stations 10 miles away that are all reporting 0-3 mph. I'll have a deeper look at wind alert because as you say it provides a lot more detail, but that virtual station was disappointing.
Another thing you need to keep in mind when viewing weather reports is where the weather station is located. Normally these are high up on top of buildings or in areas where there are wide open fields like airports etc... Most kite flying is done well below the top of high buildings and air traffic control towers. What the weather station is predicting or reporting is most likely not what you will be flying in.
That makes sense -- the closest physical weather station to my flying field is a large airport, and its weather station is probably up high and reporting more than the wind at ground level. However, what really matters to me is the direction of the wind, because my flying field is good only for a certain range of wind directions. The airport is just a few miles from the field, so I'd hope that the wind direction is at least close. So any tips for getting the direction of the wind would be helpful.
You know, I didn't think much of that site at first, but it might be helpful. Like I said before, I'm most interested in figuring out what direction the wind is coming from (or will be coming from this evening or a day or two in advance). I checked that site now, and it shows that the wind across my whole state is consistently from the same direction. That might suggest a more consistent, reliable forecast and report. If some places show north and some places show south, it's probably less reliable.