wunderground vs. nws

[Alex]

I had been under the impression that weatherunderground.com used data from the national weather service for their forecast. However, after comparing forecasts for north NJ during a recent snowstorm, there were vast discrepancies between the amount forecasted by NWS and Wunderground. NWS was more accurate with a higher amount forecasted.

Since then I have been comparing my local forecasted on the two sites, and they vary differently. Two nights recently NWS forecasted lows of 44 back to back nights. Reality were lows of 33 and 36, which wunderground covered with their 28-34 and 32-37 spread.

So, like TWC, weatherunderground uses their own data to make forecasts now? Through your experiences, which is more accurate?