A no-coverage reply (400/404) from the NWS alerts API set a single flag on wx and on the weather service that skipped every later alert request for the rest of the run, so one wx request for a city abroad silently removed alerts from every US reply after it. NWSNoCoverageCache remembers no-coverage per point rounded to two decimals, for 24 hours, at most 256 points (least recently used dropped first); a successful response clears its point, and the warning is logged once per point. The weather service polls one position, so for it the change means a retry after 24 hours instead of never.
