It's really hard to tell on the transatlantic flights, since they take different routes all the time. The jet stream is really pronounced, so you might encounter some light to moderate.
To answer your other question, we don't provide that kind of forecasting and don't recommend you change your flights based on what we forecast. It could be perfectly smooth. I'm just looking at the maps and guessing based on historical (as in, what I've seen) data based on my gut feeling.
And again, transatlantic flights are very difficult to tell.
Was this flight always on 3/6? I'm trying to figure out why I forecasted it so early. There's no way I could have forecasted it 5 days before, so the forecast is wrong. (unless you edited and changed the dates, or I misread it)
Well, there is a good chance of some bumps here and there over the ocean, and into LHR, depending on exactly what track you take (and indeed where the tracks are for that time). Probably some light to moderate at times, and also between LHR-AMS, but predominately out of LHR. Probably not what you wanted to here, but keep in mind I tend to predict 'worst case', so you are prepared.