Hi PF
You can get disturbances a surprising distance downwind from hills/mountains it all depends on the topography and windspeed. While they may not be enough to cause upsets they can make for an uncomfortable ride.
Nearer the mountains they can be very nasty indeed. My first experience of that was in fact low flying in a Jet Provost 5 in Scotland where we ran through a downdraft which gave -6g and only the "top latch" of the ejector seat stopped us being ejected. In a subsequent existence on SAR at Lossiemouth we were very aware of how the mountains can and will bite - it was a matter of pride to get through a mountain flying sortie on the up draughts rather than down draughts. You became very adept at picking the right route. If you didn't the rearcrew would always have strong advice to give you
.
As far as looking at airfield data as how the weather is in the hills it is a waste of time. Orographic effects can modify the weather alarmingly - be it pulling down the cloudbase or funnelling the wind down the valleys.
We always used to fire smoke before landing in the hills and the patterns the smoke made often showed wind speed and direction different to what you may have supposed as well as some dramatic curl unders when fired onto a ridge line.
My advice is, unless you have been well trained and have recent experience, don’t go into the hills – especially at low level.
HF