The Class 5A and 4A baseball regionals run this weekend, with eight teams advancing to next weekend’s state tournament from each 32-team bracket.

Arvada West is the No. 1 seed in 5A after it won the 5A Jeffco League and finished the regular season on an 18-game winning streak.

The Wildcats are one of the classification’s eight hosts alongside No. 2 Broomfield, No. 3 Erie, No. 4 Regis Jesuit, No. 5 Pine Creek, No. 6 Brighton, No. 7 Rocky Mountain and No. 8 Fairview.

In 4A, Palisade earned the top seed and will host alongside No. 2 Golden, No. 3 Durango, No. 4 Falcon, No. 5 Grand Junction, No. 6 Lutheran, No. 7 Pueblo County and No. 8 Canon City.

Each regional is made up of four teams, with only the champion advancing from the single-elimination tournament.

Let’s dive into a few regionals that caught our eye.

Class 5A Region 3

Teams: No. 3 Erie, No. 14 Mountain Vista, No. 19 Valor Christian and No. 30 ThunderRidge.

First round: No. 14 Mountain Vista vs. No. 19 Valor Christian, 10:30 a.m. Friday; No. 3 Erie vs. No. 30 ThunderRidge, 1 p.m. Friday.

Erie appears to be hosting the Highlands Ranch regional.

The Tigers are the favorites here for plenty of reasons, but none are bigger than ace Maddox Burnett. The BYU commit is 7-1 this season across 57 innings pitched and boasts a 1.23 ERA with 101 strikeouts. He had one so-so outing in 10 otherwise brilliant appearances on the mound this spring — an 8-2 loss to No. 2 Broomfield in which he allowed four earned runs in 5 2/3 innings.

Mountain Vista had won nine straight before ending the regular season with a loss to No. 9 Legacy. Ten days ago, the Golden Eagles beat ThunderRidge 5-0 behind a gem from Sawyer Tipton, who allowed two hits and fanned 11 in 6 1/3 innings.

Valor Christian also beat the Grizzlies during the regular season. It came last month on the back of Harrison Feagans, who drove in two runs in a 4-3 win.

Class 5A Region 8

Teams: No. 8 Fairview, No. 9 Legacy, No. 24 Boulder and No. 25 Pueblo West.

First round: No. 9 Legacy vs. No. 24 Boulder, 12:30 p.m. Saturday; No. 8 Fairview vs. No. 25 Pueblo West, TBA.

We’ve seen much of this before.

Host Fairview played both Legacy and Boulder during the regular season. The Knights beat the Lightning in league play last month and lost to the Panthers in their regular season finale Monday.

When Boulder coach John Whitehead was asked Monday what he’d think if he was paired with Fairview in the regionals, he said he didn’t believe it would happen, and also hoped it wouldn’t. But he knew anything was possible, and now he may have to beat the crosstown rival for a second time in a week to advance to the state tournament.

Boulder and Fairview are led offensively by catchers Sam Skubic and Tanner Craytor.

Skubic has driven in at least one run in 14 of his last 15 games. He’s slugging .903 with 34 RBIs this spring.

Craytor, meanwhile, is slugging 1.075 and leads 5A with nine home runs. He nearly added his 10th against Boulder, but his long fly ball came up just short, hitting the base of the center-field wall at Scott Carpenter Park.

Class 4A Region 1

Teams: No. 1 Palisade, No. 16 Widefield, No. 17 Evergreen and No. 32 Adams City.

First round: No. 16 Widefield vs. No. 17 Evergreen, 10 a.m. Saturday; No. 1 Palisade vs. No. 32 Adams City, 12:30 p.m. Saturday.

A 1-vs.-32 upset is always highly unlikely. But Adams City brings a little bit of intrigue into it as it’ll likely give the ball to 4A’s strikeout leader, Christian Ramirez.

While the competition Ramirez has faced hasn’t been elite this spring, there’s no denying his talent. He’s struck out 107 batters and owns a 1.55 ERA across 58 2/3 innings.

But Palisade is the top seed for good reason. Senior Danyel Ishida-Farmer is 9-1 and is coming off his best start of the season — a complete-game shutout to beat No. 3 Durango 1-0 on Friday.

Widefield finished second in the 4A/3A Colorado Springs Metro League behind No. 8 Canon City. The Gladiators are averaging more than eight runs per game.

Evergreen finished second in the 4A/3A Jeffco League behind No. 2 Golden. The Cougars are averaging more than nine runs per game, spurred by junior Brecken Worthington, who leads the team with seven home runs.

Class 4A Region 5

Teams: No. 5 Grand Junction, No. 12 Discovery Canyon, No. 21 Mead and No. 28 Longmont.

First round: No. 12 Discovery Canon vs. No. 21 Mead, 10 a.m. Friday; No. 5 Grand Junction vs. No. 28 Longmont, 12:30 p.m. Friday.

You could reasonably make a case for any of the four teams to win the regional.

Host Grand Junction has stellar pitching, as both ace Andrew Henderson (1.81 ERA in 46 1/3 innings pitched) and Titus Forsyth (1.12 ERA in 37 1/3 innings pitched) own ERAs under 2.

Discovery Canyon is led by the state’s home run leader, Cole Teltschik. The senior went deep for the 13th time this season in a win over No. 16 Widefield on Saturday. The Thunder are 7-1 in games in which he has homered.

Mead and Longmont, meanwhile, are battle-tested out of the 5A/4A Granite Peaks League, which includes 5A No. 2 Broomfield, No. 3 Erie and No. 8 Fairview.

Against each other last month, the Trojans went up 7-0 and held on for a 7-6 victory. Nikolai Hansen drove in three runs in the win.