In the past the not-a-raffle raffle announcements have always been published as "Ideas," so if you have "Recent Ideas" (also listed as "Recent Community Ideas") on your homepage, you'll see the announcement there.
We now also have something called "Announcements and News," and it's possible that the raffles might be announced there in the future. The "Announcements and News" block also is already on your homepage or can be moved to your homepage by customizing the page to include it.
In any case, it will be announced in plenty of time to "purchase" tickets.