[spoiler]T+0: The bombs drop. Many cities in New England are hit with high explosives. The klaxons that are supposed to warn of an attack never sound, and the strikes appear to be precisely targeted, though there isn’t much special about the areas they strike at first glance. In reality, several of the smaller labs that scatter the area providing relays for the primary dimensional manipulation experiments have experienced gateways opening in the immediate area, and their machinery refusing to shut down. Those inside have quickly been overwhelmed by extradimensional horrors. The strikes are against labs that have been overrun, or where the resonator equipment is still functioning, and locations believed to have opened portals. It is hoped the high energy yield of high explosives will collapse the portals, or at least destroy the equipment that makes it possible for them to open. In many cases, this works. In others, the strikes make things worse, changing how the portals work instead.
From several of these strikes, the portals absorb the energy and create a larger, fluctuating rift that allows noxious alien chemicals to billow forth in huge plumes. Those in the immediate area have their skin blister, boil, and slough off, and the chemicals quickly enter the atmosphere. Other areas have their portals turn into blistering infernos, or areas of extreme cold. It is hypothesized by scientists in-the-know that disrupting the lab network has caused permanent dimensional weakness and expanded our susceptibility not only to connections to the subprime plane, but also a number of neighboring planes. This is all fairly meaningless to the average citizen, who is mostly under the impression that life has turned into hell-on-earth. [/spoiler]
Doesnt specify nukes. But…
T+56 Hours: Bombing of large US cities by an unknown aggressor commences. A crippled defense infrastructure is largely unable to respond.
Also doesnt specify nukes but it could be reasoned there coulda been at larger strategic targets, and that fallout WILL drift.