Update: So it seems the event has been extended, all the way until 1st March 2019, 1pm PST (GMT-8)!
This weekend, take a break from catching Palkia and focus on raiding Latias with a small chance at getting a Shiny version of it! The event will last from Friday, Feb. 22, 2019, at 1 p.m. PST (GMT −8) to Monday, Feb. 25, 2019, at 1 p.m. PST (GMT −8) and like the recent Ho-oh and Lugia weekend, Latias will appear in regular raid battles so watch out for those black eggs!
Personally, I think its great we’re getting a shiny but I very much prefer the 3 hour raid events over the whole weekend ones. If you’re the type who will use and buy a lot of premium passes then its no issue but I prefer to conserve them for the really good legendaries like Shiny Rayquaza or any of the Hoenn Weather Trio for that matter. Latias on its own isn’t the best but it does have a Mega evolution so if Niantic should ever release that, you can at least have a good IV Latias on hand to Mega evolve.
Also, since we’re getting a Shiny Latias event, expect its brother Latios to have his own, sometime soon.