From the vast number of contributions to this thread (??) so far I do wonder how IFR pilots of sub-turboprop planes do their long range flight planning.
Years ago, before the internet, and before the internet started leaking all the precious 3D weather data which the "CAA authorised" UK Met Office wants to charge for, pilots were unable to plan things this way.
They either needed to have weather understanding bordering on that of a professional forecaster (which I still think wouldn't have done them a lot of good without access to the data; I know of some forecasters and they get their stuff off the internet too), or they just took off and went, and if they picked up an inch or two of ice which they couldn't get rid of (because the rubber boots were not up to the job, or they didn't have any) they would descend, or climb, and hope.
One could say the same for long VFR flights - they require a much more aggressive planning strategy than VFR - but it's very likely that almost nobody does those in Europe.
At the same time I do know that plenty of people who hang out here either do decent flights, or they used to. I wonder what they do, or did.
On the face of it, the SigWx should do the job if one can flight plan the route for say FL150, but IME the cloud top data on that is way off the mark. I suspect this may be because it is intended for jet pilots and they don't care much for anything enroute because they can handle it as they go along.