PS. To your latest question if you need a WX radar (vs. EFB or MFD uplink weather only): you should know that the mosaic of data displayed on your MFD is far from being "immediate" as it is obtained and processed from multiple NEXRAD sites, the information could be more then 20 minutes old (cf. NTSB safety alert on limitations of cockpit weather displays).
I just spoke to a friend of mine who flies 737s and he said what I thought previously: the weather display is real time and not lagging in time like you suggested.
Some of the smaller GA aircraft take wx info from a local station. But I assume the wx radar in the F27 uses radio waves that bounce off moisture and hence gives a real-time picture to the crew.