METAR and continuously varying weather parameters
If METAR info is available, this (rather than default tile center info) should be used to set parameters like visibility, pressure or temperature. To avoid discontinuous jumps, the info should be linearly interpolated in time for each nearby position from which a METAR is available. If METAR is updated every 10 minutes, one can use the information at startup for each position for the first 10 minutes of flight, then as soon as the next METAR is available slowly change the value (at each position) within the next 10 minutes to the values just fetched, and continue to do so (in essence creating a 10 minute offset from real to simulated weather).
How can I obtain that slow change of the weather ? Because the weather is allways changed non-continualy after all METAR changes. No interpolation, no aproximation or something else, everytime sudden and steep change. When I'm flying at FL600, this is not problem, after any METAR changes I need chceck autopilot, many times had been disengaged with baro altitude discontinuity. In one second is sky below me fully covered with clouds and second later I can't see any clouds. It is annoying in high altitude, but somewhere in the Alps valley - it is ticket to the hell.