It means it will get sold off tomorrow. People will "sell the news." Generally when these analysts are stuck with any stock, they upgrade it for the retail investors to buy and they exit. Now people don't buy the "upgrades" anymore.
Not true. Then why it goes down when downgrade comes.
don't be too naive. Do you really think analysts give up "upgrades" real time? They load up cheap, then upgrade the stock and unload when retail investors get in.
Downgrades don't affect stocks much or much longer, unless there is a significant evidence of a negative incident.