Kitchen sink is backed up. It eventually drains ( like hours later) and backs up enough I can't run dishwasher. Have tried the usual fixes that haven't help at all. No luck with the plunger, removing/making sure p-trap is clean, disposal is clean so figuring it must be between where it enters/leaves the kitchen. Have a 15 foot snake and that didn't help things either. Nothing else in the house is backed up so seems isolated to kitchen sink. Fear it's out away from the house but wanted to try every possible fix before calling the plumber. Any ideas? Tips? Longer Snake worth a shot? or just call the plumber?

BIG THANKS in advance!