ACR FLC DEVIATE DUE TO WX FACTORS; BUT DO NOT ADVISE CZQM. ATC CHALLENGES OFF RTE FLT.

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I WAS THE PNF. WE WERE EXPERIENCING CONTINUOUS LIGHT TO MODERATE TURB FOR THE PAST 30 MINS OR SO. MANY ACFT WERE RPTING THE SAME CONDITIONS. WE WERE ABOUT 20 MI FROM CYMON; OUR COAST-OUT FIX. THERE WAS AN ACFT AHEAD AND ABOVE US. CAPT THOUGHT TURB MAY BE RELATED TO THAT ACFT. I LEFT THE COCKPIT TO USE THE LAVATORY. I RETURNED APPROX 5 MINS LATER. CAPT TOLD ME THAT HE OFFSET 3 MI FOR AVOIDING POSSIBLE TURB FROM ACFT AHEAD. ABOUT 1 MIN OR SO LATER; CTR ASKED IF WE WERE GOING DIRECT TO CYMON. I SAID YES; THINKING THE CAPT TOLD HIM ABOUT THE OFFSET. AS IT TURNED OUT; CAPT NEVER TOLD CTR THAT HE WAS OFFSETTING. CAPT THEN TOLD CTR THAT HE HAD OFFSET. CTR REPLIED 'OK.' THERE WAS NEVER A SEPARATION PROB AND CTR DID NOT SEEM TOO CONCERNED. WHEN CTR ASKED US IF WE WERE GOING DIRECT TO CYMON; I WAS ALSO THINKING HE WAS CONFIRMING OUR COAST-OUT FIX. SINCE WE WERE STILL IN RADAR CONTACT; CTR SAW THAT WE WERE NOT GOING WHERE HE THOUGHT WE SHOULD BE. CAPT DID NOT THINK HE COULD SEE US ON RADAR. AGAIN; THERE WERE NO CONFLICTS. I SHOULD HAVE NOT ASSUMED THAT THE CAPT HAD TOLD CTR. I SHOULD HAVE ASKED.