PacWest, Western Alliance stocks plunge as US regional banking woes worsen

First Republic's collapse, the third major casualty of the biggest crisis to hit the U.S. banking sector since 2008, rekindled a slide in shares of regional lenders this week despite regulatory efforts to staunch the turmoil that began with the collapse of Silicon Valley Bank in March. "Nobody knows where these banks should be trading at because what we saw with Silicon Valley Bank is that the fundamentals can change so quickly," said Tom Plumb, portfolio manager at Plumb Balanced Fund in Madison, Wisconsin.