Dispatcher reported the alternate airport they added to the flight release was not valid because it did not meet the new weather requirements that the airline established due to 5G NOTAMs.

Narrative

During my shift the night of Date; I was very busy due to the weather situation across [area] with many aerodromes in the IFR-LIFR range. I was selecting alternates that were +1:00 away from airports in southern [area]. Originally I just had ZZZ1 on the release; but selected a second alternate of ZZZ2. The original release was sent with two alternates ZZZ2 and ZZZ1. ZZZ2 was illegal due to the new policy of alternate selection of weather at less 600-2 due to the 5G NOTAMS. I saw the weather had been forecast just below weather alternate minimums. I ACARS the crew and had them remove ZZZ2 from the release since weather was forecast below alternate mins. The biggest thing is the increase in alternate minimums; which recently changed. High workload for the west central region during the shift due to IFR-LIFR conditions across the worked region. Flight was released late due to meteorology writing an exception TAF for ZZZ3 around XA00Z when all the Routine TAFs go out. Meteorology had been busy issuing the XAZ company TAFs. First; better diligence on my part on knowing the new policy in place now for adding an alternate. I did add ZZZ2 has a second alternate with ZZZ1 as the primary. Second; newer flight planning system that highlights closures; alternates or greys out them out as an options (an AI intelligence) that is able to tell us if an alternate is legal to use or not with forecast weather.