Since the legacies often match WN fares, using Google Flights in map view mode and selecting legacy carriers generally works pretty well for finding lowest WN fares even though Google Flights doesn't actually show WN fares. Probably best to wait for another WN fare sale (which generally run Tue-Thu) and look for flights in the Fall (Tue/Wed/Sat flights are generally cheapest). You don't list which cities you are looking at flying out of, so I'm assuming you will be flying out of what's listed in your profile. Currently, if you are looking out of BNA, BNA-LGA is available from $54 for Tue/Wed/Sat flights in late August and the Fall. Out of FLL, FLL-RDU is available for $74.