We live in an age when any nation can get overhead photos in multiple spectrums far better than those available to the US and the Soviet Union in the 1960s and 70s from commercial satellites. Syria might well be responding to Israeli preparations for a large military operation. Sometimes such preparations make it clear what the intentions of the nation making them are. Other times it is not apparent. Last spring there was a lot of Israeli talk about a war with Syria. More recent events in Gaza have drawn attention there. It would appear that the Syrian activity is an enhanced defensive posture. In which case they might well be hedging a bet that the thunderbolt will land on Gaza.
Shaffir to Herzog: Opposition failed to show leadership in political battles against PM (Haaretz)
from the article: MI: Syria increases military activity for fear of an Israeli attack