737NG, FS2002, Real Weather

Good morning Captains, PMDG Staff and anybody else:-)just enroute from EDDT to LEMD at FL370 using real world weather/winds aloft (GetWeather 3.0) in FS2002, i had to realize some strange effects that i did several times ago:the altimeter jumps(!) - not moves - several hundreds of feet up/down as well as the speedtape, VNAV of course is lost. but the ND doesn't show any changes of windspeed/direction. So i thought there might by some turbulences/jetstreams and decided to change from FL370 to FL240 and restart VNAV after changing the CRZ ALT in FMC.But the story continues:-) Taking a close look at the ND i could see that obviously the weather information is lost for a few moments and then comes back, because the wind information in the top left corner of the ND is gone for a few seconds and returns a few seconds later. That is - of course - the reason for the "jumoing" altimeter due to the sudden change of air pressure i suppose.But - does anybody have an explanation for that?Aircraft is 737-700 (boxed version)Looking forward for your answers,kind regards