By Anthony Gulizia, Globe correspondent

The state basketball tournament is always filled with upsets, and any team can make a run at anytime. It's a clean slate for the .500 teams and a chance to salvage a sub-par season, while the finest teams in the state look to assert their dominance.

Anything is possible once the tournament heats up, but there's one thing you can count on - the Division 1 North tourney is going to be a barn-burner.

On one side of the bracket, No.1 St John's Prep (19-1), No. 2 Central Catholic (19-2), No. 5 Charlestown (20-2) and No. 12 East Boston (15-5) are seeded.

The Prep has a bye and will face the winner of tomorrow's Billerica (10-10)/Boston Latin (11-11) preliminary contest, which takes place Friday at 7 p.m.

East Boston travels to Lincoln-Sudbury (17-3) Wednesday, Charlestown will host Methuen (12-8) Wednesday and Central Catholic will welcome Lexington (12-8) tomorrow.

Barring any upsets, the stage is set for a semi-final rematch between St. John's Prep and Central Catholic. The Prep took down Central in the last game of the regular season courtesy of a go-ahead layup by Pat Connaughton in the weining seconds of the game.

Likewise, there's the possibility that Charlestown sneaks past Central Catholic and faces the Prep in the final. The townies dealt the Eagles the only blemish on their record earlier this year.

The scenarios go on. If the city squads pull off the upsets of the most feared private schools, Eastie can possibly face Charlestown in a rematch of the Boston City League championship in which the Townies won.

Any way you cut it, you can bank on a great semi-final game in that half of the bracket and a great finals match, cause don't forget there's another side to this.

There's a great matchup between Acton-Boxboro (18-3) Andover (14-5) tomorrow at 7 p.m. The Colonials battled for Dual County League supremacy with Westfrod and LS this season and came out on top. But Andover is no slouch, so keep an eye on this one.

It's unlikely that Lynn English (19-2) will fall to Everett (12-8) in the first round, so expect a marquee matchup between the English and the AB/Andover winner.

Cambridge (19-1) will face the winner of tomorrow's Chelmsford (8-12)/Lawrence (12-8) game, Friday at 7 p.m.. The winner of that contest will face the winner of tomorrow's the Westford (17-3)/Somerville (16-4).

This side of the bracket is wide open, and there is no sure pick. Not even Lynn English or Cambridge are safe, especially with Somerville in the way, who beat Cambridge earlier this season. Andover upset Central Catholic earlier this season as well, and Westford Academy can certainly bang with the best.

The North is about to get wild.\

Finals Prediction: St. John's Prep 74, Acton-Boxboro 68 - AB's dynamic duo of Sam Longwell and Wes Schroll, combined with facing a tough DCL schedule has the Colonials primed for a run at the title. But in the end, Pat Connaughton and his strong supporting cast of Steve Haladyna and Mike Carbone will prove to be too tough. The Prep has a deep lineup, and that makes for a deep tournament run.

In the South, Mansfield (20-2) will take on the winner of tomorrow's Needham (11-9)/North Quincy (10-10) contest, Thursday at 7 p.m.

There's no doubt Mansfield will get through to the quarterfinals, and they'll await the winner Thursday's Madison Park (12-6)/Franklin (13-7). MP takes on a tough Franklin team that took down Charlestown earlier this season, but Madison Park's experience from last year's late run to the Garden can serve them well.

Marshfield (15-3) is the strong suit in the lower left half of the bracket, but they face a strong (12-8) BC High team Thursday at 7 p.m. Don't be fooled by BC's record, as they took out No. 7 Acton-Boxboro and Newton North.

Meanwhile, the stage is set for a Newton North (16-6)/Weymouth (17-3) quarterfinal. Weymouth takes on the winner of tomorrow's Taunton (10-8)/Xaverian (10-10) contest, Thursday at 7 p.m.

Newton North will take on North Attleboro (13-7) Thursday at 7 p.m.

And last, but not least, Brockton (13-7) takes on West Roxbury (15-6) Thursday at 7 p.m. New Bedford (16-3) takes on Barnstable (11-8) Thursday at 7 p.m. as well. Look for a New Bedford/Brockton quarterfinal, but keep a lookout for Westie, who could give Brockton a hard time in the early matchup.

Finals Prediction - Madison Park 74, Weymouth 70. Madison Park faced a tough schedule in the Boston City League, and the experience the team has from last year's title run is going to fuel the Cardinal's fire. Weymouth also survived a tough Bay-State run and their fast-paced offense can hang with MP.

That wraps up the tournament preview, check in for tournament updates and a final Top 20 will follow at the end of the tournament.