The OP asks the question... when Jesus comes back, will there be a preceding announcement or warning?
Or will it happen suddenly and quickly?
Matt 24:42; "Therefore be on the alert, for you do not know which day your Lord is coming.
Matt 24:43; "But be sure of this, that if the head of the house had known at what time of the night the thief was coming, he would have been on the alert and would not have allowed his house to be broken into.
Matt 24:44; "For this reason you also must be ready; for the Son of Man is coming at an hour when you do not think He will.
Luke 12:35; "Be dressed in readiness, and keep your lamps lit.
Luke 12:36; "Be like men who are waiting for their master when he returns from the wedding feast, so that they may immediately open the door to him when he comes and knocks.
Luke 12:37; "Blessed are those slaves whom the master will find on the alert when he comes; truly I say to you, that he will gird himself to serve, and have them recline at the table, and will come up and wait on them.
Luke 12:38; "Whether he comes in the second watch, or even in the third, and finds them so, blessed are those slaves.
Luke 12:39; "But be sure of this, that if the head of the house had known at what hour the thief was coming, he would not have allowed his house to be broken into.
Luke 12:40; "You too, be ready; for the Son of Man is coming at an hour that you do not expect."
Luke 12:41; Peter said, "Lord, are You addressing this parable to us, or to everyone else as well?"
Luke 12:42; And the Lord said, "Who then is the faithful and sensible steward, whom his master will put in charge of his servants, to give them their rations at the proper time?
Luke 12:43; "Blessed is that slave whom his master finds so doing when he comes.
Some people say these warnings are for unbelievers, but Peter asks Jesus is this message for us also? Read Jesus's reply. Verse 35 above says keep your lamps lit... does this remind you of Matt 25:8; ?
1Thes; 5:2 For you yourselves know full well that the day of the Lord will come just like a thief in the night.
1Thes; 5:3 While they are saying, "Peace and safety!" then destruction will come upon them suddenly like labor pains upon a woman with child, and they will not escape.
1Thes; 5:4 But you, brethren, are not in darkness, that the day would overtake you like a thief;
1Thes; 5:5 for you are all sons of light and sons of day. We are not of night nor of darkness;
1Thes; 5:6 so then let us not sleep as others do, but let us be alert and sober.
1Thes; 5:7 For those who sleep do their sleeping at night, and those who get drunk get drunk at night.
2Pet 3:10; But the day of the Lord will come like a thief, in which the heavens will pass away with a roar and the elements will be destroyed with intense heat, and the earth and its works will be burned up.
2Pet 3:11; Since all these things are to be destroyed in this way, what sort of people ought you to be in holy conduct and godliness,
2Pet 3:12; looking for and hastening the coming of the day of God, because of which the heavens will be destroyed by burning, and the elements will melt with intense heat!
Rev 16:15; ("Behold, I am coming like a thief. Blessed is the one who stays awake and keeps his clothes, so that he will not walk about naked and men will not see his shame.")