I experienced the same problem yesterday afternoon. I checked and updated all my references to the forecast in Settings.php, advforecast2.php, and forecast-summary.php after which my local forecast reappeared. (BFSkinner, a psychologist who studied rat behavior, was correct when he stated that random positive reinforcement leads to the most persistent repetitive behavior, because I would probably do the same thing even though it likely didn't do anything to correct the problem.
) I have no idea what happened or how it was resolved. All of my other forecasts would display. How could the cache get frozen on empty like that?