Hello!

I have seen such a headline in online press: 

İstanbul´da sabah saatlerinde etkili olmaya başlayan kar yağışı Anadolu yakasının yüksek kesimlerini beyaza bürüdü

My try to translate is: Snowfall which began to be strong in morning hours in Istanbul, covered up to white the high parts of its Anatolia side. Tell me please if my translation is good, because I was unsure about the part in red.. first I thought Anadolu yakası is a full phrase for side of Anadolia, but later I´ve come to conclusion that the -si suffix refers to Istanbul [its (Istanbul´s) Anadolia side]. But I´m still not sure about it, and hoping for explanation

The possessive suffix must be in its place because it ties yaka with Anadolu. It is enough reason. But I suspect it also connects the whole package to İstanbul.

In the compound

         İstanbul [Anadolu yaka|sı]

yaka is modified by Anadolu and Anadolu yakası is modified by İstanbul. The syntactic structure is the same like in

         lokantanın [yemek menü|sü].

Double possessives are not used, though.

Actually your compound continues and there is always one possessive suffix in each owned:

         İstanbul [Anadolu yaka|sı|n|ın] [yüksek kesim|ler|i|n|i]

There is a detailed lesson about compounds in the Turkish lessons section (Pagliaccio: Tamlamalar).

sufler, you deserve a better explanation than this and hopefully you will get it, but it seems quiet today. At least the lesson I mentioned will help you inşallah.

 Anadolu yakası = Asian side (we don´t say anatolian side in English).

Your first thoughts are right. The -sı relates to Anadolu.

In Istanbul, the snow which started to be heavy in the morning, covered the high parts of the Asian side in white.