I can understand why they get predictions about the future wrong, that bit is hard. What gets me is when the prediction for right now is at odds with what is actually happening. It seems like there is a significant delay between sensors on the ground taking a reading and the models being updated.
I'm not a Met, but I do have some understanding of the processes involved in model forecast runs.
Both the ECMWF and the US's GFS V2 (which, incidentally, is normally trounced by the ECMWF when it comes to predictive qualities) rely on a global network of real-time pressure and temperature sensors. Every six hours, that data is assembled into the databases needed for the ECMWF (and GFS, GEM, JAMSTEC etc) to run. They crunch the numbers and spit out a forecast, starting 6 hours out from the initialization conditions.
Apart from it being slightly comical when the guy on TV says sun is out but looking through the window I can see rain, it makes short term predictions useless. If they say it will rain this evening when I want to go out but the forecast for right now is wrong, what am I supposed to do with that information?
Back in the days when Pluto was still a planet and Bill Crosby wasn't creepy, the local TV stations actually employed a meteorologist to do their short-range forecasting (or had an agreement with the local airport or whatever). That guy (usually an older guy) would draw the maps and explain the weather, and usually get it right (with, of course, the obviously insane errors). Since that guy was doing local forecasts (and note the airport comment; planes need really good local weather to land, or at least they did; I'm not sure about today), it was actionable information.
Fast forward to today, and you see a TV personality showing off a narrow waist and ample cleavage whilst presenting the weather. They are reading off model forecasts that may or may not bear much resemblance to your reality. That crap is at best guidance only; and hardly actionable for this evening.
If you want to have actionable rain information, I've read about an app called Dark Sky (note: I have nothing to do with this app; it's feature set and how it works caught my attention). It uses the pressure and temperature information that comes from your phone (and app users around you) to build a local-to-you forecast. My iPhone 4S doesn't have the necessary sensors, so I've not really followed up with the app, but I have heard lots of good things. YMMV.