Turns out that the sunroof drains on both sides were completely clogged with years of dirt and leaf debris. These drain tubes run down through the front A-pillars and are easily clogged, requiring annual (possibly semi-annual) routine maintenance.
I used flexible insulated wire inserted in the drain hold while the sunroof is open to clear the tubes. Ran the wire down the tubing on both sides all the way to the undercarriage. After clearing the debris, used a bottle of water at the drain holes to clear out the remnants left inside the tubing. A good trickle of water coming out from inside the wheel wells will indicate clear drain tubes.
YouTube video explaining how to do this maintenance: https://www.youtube.com/watch?v=E8B9NfayNf0
Drying out the carpeting was a whole different adventure....