The area to the North of IST is very much different from the environment at IST. About 5km north you have rolling hills up to about 700' AMSL (IST is about 10' AMSL) with dense vegetation and forests. It absolutely 100% has it's own microclimate there. If they have no specific weather info from the area north of IST (and there are no airfields there so there is nothing accessible) then I suspect you could easily find suitable weather to launch at IST and a situation not close to being VFR in the region to the north.
IST is one of the world's busiest airports, a FW ac departs there every 50 seconds and lands on a different runway at roughly the same interval. The controllers hate RW traffic there as it interferes with the FW too much. From memory there is a speed restriction coming in of about 160kts minimum, hence no IFR for RW. Basically once the RW depart the ramp up by the VIP/ GA terminal, no one cares what you do and no one is really watching, certainly not in real time.
Just my experience of the area though.